| 1 | /* |
| 2 | * linux/mm/vmscan.c |
| 3 | * |
| 4 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
| 5 | * |
| 6 | * Swap reorganised 29.12.95, Stephen Tweedie. |
| 7 | * kswapd added: 7.1.96 sct |
| 8 | * Removed kswapd_ctl limits, and swap out as many pages as needed |
| 9 | * to bring the system back to freepages.high: 2.4.97, Rik van Riel. |
| 10 | * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). |
| 11 | * Multiqueue VM started 5.8.00, Rik van Riel. |
| 12 | */ |
| 13 | |
| 14 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| 15 | |
| 16 | #include <linux/mm.h> |
| 17 | #include <linux/module.h> |
| 18 | #include <linux/gfp.h> |
| 19 | #include <linux/kernel_stat.h> |
| 20 | #include <linux/swap.h> |
| 21 | #include <linux/pagemap.h> |
| 22 | #include <linux/init.h> |
| 23 | #include <linux/highmem.h> |
| 24 | #include <linux/vmpressure.h> |
| 25 | #include <linux/vmstat.h> |
| 26 | #include <linux/file.h> |
| 27 | #include <linux/writeback.h> |
| 28 | #include <linux/blkdev.h> |
| 29 | #include <linux/buffer_head.h> /* for try_to_release_page(), |
| 30 | buffer_heads_over_limit */ |
| 31 | #include <linux/mm_inline.h> |
| 32 | #include <linux/backing-dev.h> |
| 33 | #include <linux/rmap.h> |
| 34 | #include <linux/topology.h> |
| 35 | #include <linux/cpu.h> |
| 36 | #include <linux/cpuset.h> |
| 37 | #include <linux/compaction.h> |
| 38 | #include <linux/notifier.h> |
| 39 | #include <linux/rwsem.h> |
| 40 | #include <linux/delay.h> |
| 41 | #include <linux/kthread.h> |
| 42 | #include <linux/freezer.h> |
| 43 | #include <linux/memcontrol.h> |
| 44 | #include <linux/delayacct.h> |
| 45 | #include <linux/sysctl.h> |
| 46 | #include <linux/oom.h> |
| 47 | #include <linux/prefetch.h> |
| 48 | #include <linux/printk.h> |
| 49 | #include <linux/dax.h> |
| 50 | |
| 51 | #include <asm/tlbflush.h> |
| 52 | #include <asm/div64.h> |
| 53 | |
| 54 | #include <linux/swapops.h> |
| 55 | #include <linux/balloon_compaction.h> |
| 56 | |
| 57 | #include "internal.h" |
| 58 | |
| 59 | #define CREATE_TRACE_POINTS |
| 60 | #include <trace/events/vmscan.h> |
| 61 | |
| 62 | struct scan_control { |
| 63 | /* How many pages shrink_list() should reclaim */ |
| 64 | unsigned long nr_to_reclaim; |
| 65 | |
| 66 | /* This context's GFP mask */ |
| 67 | gfp_t gfp_mask; |
| 68 | |
| 69 | /* Allocation order */ |
| 70 | int order; |
| 71 | |
| 72 | /* |
| 73 | * Nodemask of nodes allowed by the caller. If NULL, all nodes |
| 74 | * are scanned. |
| 75 | */ |
| 76 | nodemask_t *nodemask; |
| 77 | |
| 78 | /* |
| 79 | * The memory cgroup that hit its limit and as a result is the |
| 80 | * primary target of this reclaim invocation. |
| 81 | */ |
| 82 | struct mem_cgroup *target_mem_cgroup; |
| 83 | |
| 84 | /* Scan (total_size >> priority) pages at once */ |
| 85 | int priority; |
| 86 | |
| 87 | /* The highest zone to isolate pages for reclaim from */ |
| 88 | enum zone_type reclaim_idx; |
| 89 | |
| 90 | unsigned int may_writepage:1; |
| 91 | |
| 92 | /* Can mapped pages be reclaimed? */ |
| 93 | unsigned int may_unmap:1; |
| 94 | |
| 95 | /* Can pages be swapped as part of reclaim? */ |
| 96 | unsigned int may_swap:1; |
| 97 | |
| 98 | /* Can cgroups be reclaimed below their normal consumption range? */ |
| 99 | unsigned int may_thrash:1; |
| 100 | |
| 101 | unsigned int hibernation_mode:1; |
| 102 | |
| 103 | /* One of the zones is ready for compaction */ |
| 104 | unsigned int compaction_ready:1; |
| 105 | |
| 106 | /* Incremented by the number of inactive pages that were scanned */ |
| 107 | unsigned long nr_scanned; |
| 108 | |
| 109 | /* Number of pages freed so far during a call to shrink_zones() */ |
| 110 | unsigned long nr_reclaimed; |
| 111 | }; |
| 112 | |
| 113 | #ifdef ARCH_HAS_PREFETCH |
| 114 | #define prefetch_prev_lru_page(_page, _base, _field) \ |
| 115 | do { \ |
| 116 | if ((_page)->lru.prev != _base) { \ |
| 117 | struct page *prev; \ |
| 118 | \ |
| 119 | prev = lru_to_page(&(_page->lru)); \ |
| 120 | prefetch(&prev->_field); \ |
| 121 | } \ |
| 122 | } while (0) |
| 123 | #else |
| 124 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) |
| 125 | #endif |
| 126 | |
| 127 | #ifdef ARCH_HAS_PREFETCHW |
| 128 | #define prefetchw_prev_lru_page(_page, _base, _field) \ |
| 129 | do { \ |
| 130 | if ((_page)->lru.prev != _base) { \ |
| 131 | struct page *prev; \ |
| 132 | \ |
| 133 | prev = lru_to_page(&(_page->lru)); \ |
| 134 | prefetchw(&prev->_field); \ |
| 135 | } \ |
| 136 | } while (0) |
| 137 | #else |
| 138 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) |
| 139 | #endif |
| 140 | |
| 141 | /* |
| 142 | * From 0 .. 100. Higher means more swappy. |
| 143 | */ |
| 144 | int vm_swappiness = 60; |
| 145 | /* |
| 146 | * The total number of pages which are beyond the high watermark within all |
| 147 | * zones. |
| 148 | */ |
| 149 | unsigned long vm_total_pages; |
| 150 | |
| 151 | static LIST_HEAD(shrinker_list); |
| 152 | static DECLARE_RWSEM(shrinker_rwsem); |
| 153 | |
| 154 | #ifdef CONFIG_MEMCG |
| 155 | static bool global_reclaim(struct scan_control *sc) |
| 156 | { |
| 157 | return !sc->target_mem_cgroup; |
| 158 | } |
| 159 | |
| 160 | /** |
| 161 | * sane_reclaim - is the usual dirty throttling mechanism operational? |
| 162 | * @sc: scan_control in question |
| 163 | * |
| 164 | * The normal page dirty throttling mechanism in balance_dirty_pages() is |
| 165 | * completely broken with the legacy memcg and direct stalling in |
| 166 | * shrink_page_list() is used for throttling instead, which lacks all the |
| 167 | * niceties such as fairness, adaptive pausing, bandwidth proportional |
| 168 | * allocation and configurability. |
| 169 | * |
| 170 | * This function tests whether the vmscan currently in progress can assume |
| 171 | * that the normal dirty throttling mechanism is operational. |
| 172 | */ |
| 173 | static bool sane_reclaim(struct scan_control *sc) |
| 174 | { |
| 175 | struct mem_cgroup *memcg = sc->target_mem_cgroup; |
| 176 | |
| 177 | if (!memcg) |
| 178 | return true; |
| 179 | #ifdef CONFIG_CGROUP_WRITEBACK |
| 180 | if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) |
| 181 | return true; |
| 182 | #endif |
| 183 | return false; |
| 184 | } |
| 185 | #else |
| 186 | static bool global_reclaim(struct scan_control *sc) |
| 187 | { |
| 188 | return true; |
| 189 | } |
| 190 | |
| 191 | static bool sane_reclaim(struct scan_control *sc) |
| 192 | { |
| 193 | return true; |
| 194 | } |
| 195 | #endif |
| 196 | |
| 197 | /* |
| 198 | * This misses isolated pages which are not accounted for to save counters. |
| 199 | * As the data only determines if reclaim or compaction continues, it is |
| 200 | * not expected that isolated pages will be a dominating factor. |
| 201 | */ |
| 202 | unsigned long zone_reclaimable_pages(struct zone *zone) |
| 203 | { |
| 204 | unsigned long nr; |
| 205 | |
| 206 | nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) + |
| 207 | zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE); |
| 208 | if (get_nr_swap_pages() > 0) |
| 209 | nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) + |
| 210 | zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON); |
| 211 | |
| 212 | return nr; |
| 213 | } |
| 214 | |
| 215 | unsigned long pgdat_reclaimable_pages(struct pglist_data *pgdat) |
| 216 | { |
| 217 | unsigned long nr; |
| 218 | |
| 219 | nr = node_page_state_snapshot(pgdat, NR_ACTIVE_FILE) + |
| 220 | node_page_state_snapshot(pgdat, NR_INACTIVE_FILE) + |
| 221 | node_page_state_snapshot(pgdat, NR_ISOLATED_FILE); |
| 222 | |
| 223 | if (get_nr_swap_pages() > 0) |
| 224 | nr += node_page_state_snapshot(pgdat, NR_ACTIVE_ANON) + |
| 225 | node_page_state_snapshot(pgdat, NR_INACTIVE_ANON) + |
| 226 | node_page_state_snapshot(pgdat, NR_ISOLATED_ANON); |
| 227 | |
| 228 | return nr; |
| 229 | } |
| 230 | |
| 231 | bool pgdat_reclaimable(struct pglist_data *pgdat) |
| 232 | { |
| 233 | return node_page_state_snapshot(pgdat, NR_PAGES_SCANNED) < |
| 234 | pgdat_reclaimable_pages(pgdat) * 6; |
| 235 | } |
| 236 | |
| 237 | unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru) |
| 238 | { |
| 239 | if (!mem_cgroup_disabled()) |
| 240 | return mem_cgroup_get_lru_size(lruvec, lru); |
| 241 | |
| 242 | return node_page_state(lruvec_pgdat(lruvec), NR_LRU_BASE + lru); |
| 243 | } |
| 244 | |
| 245 | /* |
| 246 | * Add a shrinker callback to be called from the vm. |
| 247 | */ |
| 248 | int register_shrinker(struct shrinker *shrinker) |
| 249 | { |
| 250 | size_t size = sizeof(*shrinker->nr_deferred); |
| 251 | |
| 252 | if (shrinker->flags & SHRINKER_NUMA_AWARE) |
| 253 | size *= nr_node_ids; |
| 254 | |
| 255 | shrinker->nr_deferred = kzalloc(size, GFP_KERNEL); |
| 256 | if (!shrinker->nr_deferred) |
| 257 | return -ENOMEM; |
| 258 | |
| 259 | down_write(&shrinker_rwsem); |
| 260 | list_add_tail(&shrinker->list, &shrinker_list); |
| 261 | up_write(&shrinker_rwsem); |
| 262 | return 0; |
| 263 | } |
| 264 | EXPORT_SYMBOL(register_shrinker); |
| 265 | |
| 266 | /* |
| 267 | * Remove one |
| 268 | */ |
| 269 | void unregister_shrinker(struct shrinker *shrinker) |
| 270 | { |
| 271 | down_write(&shrinker_rwsem); |
| 272 | list_del(&shrinker->list); |
| 273 | up_write(&shrinker_rwsem); |
| 274 | kfree(shrinker->nr_deferred); |
| 275 | } |
| 276 | EXPORT_SYMBOL(unregister_shrinker); |
| 277 | |
| 278 | #define SHRINK_BATCH 128 |
| 279 | |
| 280 | static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, |
| 281 | struct shrinker *shrinker, |
| 282 | unsigned long nr_scanned, |
| 283 | unsigned long nr_eligible) |
| 284 | { |
| 285 | unsigned long freed = 0; |
| 286 | unsigned long long delta; |
| 287 | long total_scan; |
| 288 | long freeable; |
| 289 | long nr; |
| 290 | long new_nr; |
| 291 | int nid = shrinkctl->nid; |
| 292 | long batch_size = shrinker->batch ? shrinker->batch |
| 293 | : SHRINK_BATCH; |
| 294 | |
| 295 | freeable = shrinker->count_objects(shrinker, shrinkctl); |
| 296 | if (freeable == 0) |
| 297 | return 0; |
| 298 | |
| 299 | /* |
| 300 | * copy the current shrinker scan count into a local variable |
| 301 | * and zero it so that other concurrent shrinker invocations |
| 302 | * don't also do this scanning work. |
| 303 | */ |
| 304 | nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0); |
| 305 | |
| 306 | total_scan = nr; |
| 307 | delta = (4 * nr_scanned) / shrinker->seeks; |
| 308 | delta *= freeable; |
| 309 | do_div(delta, nr_eligible + 1); |
| 310 | total_scan += delta; |
| 311 | if (total_scan < 0) { |
| 312 | pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n", |
| 313 | shrinker->scan_objects, total_scan); |
| 314 | total_scan = freeable; |
| 315 | } |
| 316 | |
| 317 | /* |
| 318 | * We need to avoid excessive windup on filesystem shrinkers |
| 319 | * due to large numbers of GFP_NOFS allocations causing the |
| 320 | * shrinkers to return -1 all the time. This results in a large |
| 321 | * nr being built up so when a shrink that can do some work |
| 322 | * comes along it empties the entire cache due to nr >>> |
| 323 | * freeable. This is bad for sustaining a working set in |
| 324 | * memory. |
| 325 | * |
| 326 | * Hence only allow the shrinker to scan the entire cache when |
| 327 | * a large delta change is calculated directly. |
| 328 | */ |
| 329 | if (delta < freeable / 4) |
| 330 | total_scan = min(total_scan, freeable / 2); |
| 331 | |
| 332 | /* |
| 333 | * Avoid risking looping forever due to too large nr value: |
| 334 | * never try to free more than twice the estimate number of |
| 335 | * freeable entries. |
| 336 | */ |
| 337 | if (total_scan > freeable * 2) |
| 338 | total_scan = freeable * 2; |
| 339 | |
| 340 | trace_mm_shrink_slab_start(shrinker, shrinkctl, nr, |
| 341 | nr_scanned, nr_eligible, |
| 342 | freeable, delta, total_scan); |
| 343 | |
| 344 | /* |
| 345 | * Normally, we should not scan less than batch_size objects in one |
| 346 | * pass to avoid too frequent shrinker calls, but if the slab has less |
| 347 | * than batch_size objects in total and we are really tight on memory, |
| 348 | * we will try to reclaim all available objects, otherwise we can end |
| 349 | * up failing allocations although there are plenty of reclaimable |
| 350 | * objects spread over several slabs with usage less than the |
| 351 | * batch_size. |
| 352 | * |
| 353 | * We detect the "tight on memory" situations by looking at the total |
| 354 | * number of objects we want to scan (total_scan). If it is greater |
| 355 | * than the total number of objects on slab (freeable), we must be |
| 356 | * scanning at high prio and therefore should try to reclaim as much as |
| 357 | * possible. |
| 358 | */ |
| 359 | while (total_scan >= batch_size || |
| 360 | total_scan >= freeable) { |
| 361 | unsigned long ret; |
| 362 | unsigned long nr_to_scan = min(batch_size, total_scan); |
| 363 | |
| 364 | shrinkctl->nr_to_scan = nr_to_scan; |
| 365 | ret = shrinker->scan_objects(shrinker, shrinkctl); |
| 366 | if (ret == SHRINK_STOP) |
| 367 | break; |
| 368 | freed += ret; |
| 369 | |
| 370 | count_vm_events(SLABS_SCANNED, nr_to_scan); |
| 371 | total_scan -= nr_to_scan; |
| 372 | |
| 373 | cond_resched(); |
| 374 | } |
| 375 | |
| 376 | /* |
| 377 | * move the unused scan count back into the shrinker in a |
| 378 | * manner that handles concurrent updates. If we exhausted the |
| 379 | * scan, there is no need to do an update. |
| 380 | */ |
| 381 | if (total_scan > 0) |
| 382 | new_nr = atomic_long_add_return(total_scan, |
| 383 | &shrinker->nr_deferred[nid]); |
| 384 | else |
| 385 | new_nr = atomic_long_read(&shrinker->nr_deferred[nid]); |
| 386 | |
| 387 | trace_mm_shrink_slab_end(shrinker, nid, freed, nr, new_nr, total_scan); |
| 388 | return freed; |
| 389 | } |
| 390 | |
| 391 | /** |
| 392 | * shrink_slab - shrink slab caches |
| 393 | * @gfp_mask: allocation context |
| 394 | * @nid: node whose slab caches to target |
| 395 | * @memcg: memory cgroup whose slab caches to target |
| 396 | * @nr_scanned: pressure numerator |
| 397 | * @nr_eligible: pressure denominator |
| 398 | * |
| 399 | * Call the shrink functions to age shrinkable caches. |
| 400 | * |
| 401 | * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set, |
| 402 | * unaware shrinkers will receive a node id of 0 instead. |
| 403 | * |
| 404 | * @memcg specifies the memory cgroup to target. If it is not NULL, |
| 405 | * only shrinkers with SHRINKER_MEMCG_AWARE set will be called to scan |
| 406 | * objects from the memory cgroup specified. Otherwise, only unaware |
| 407 | * shrinkers are called. |
| 408 | * |
| 409 | * @nr_scanned and @nr_eligible form a ratio that indicate how much of |
| 410 | * the available objects should be scanned. Page reclaim for example |
| 411 | * passes the number of pages scanned and the number of pages on the |
| 412 | * LRU lists that it considered on @nid, plus a bias in @nr_scanned |
| 413 | * when it encountered mapped pages. The ratio is further biased by |
| 414 | * the ->seeks setting of the shrink function, which indicates the |
| 415 | * cost to recreate an object relative to that of an LRU page. |
| 416 | * |
| 417 | * Returns the number of reclaimed slab objects. |
| 418 | */ |
| 419 | static unsigned long shrink_slab(gfp_t gfp_mask, int nid, |
| 420 | struct mem_cgroup *memcg, |
| 421 | unsigned long nr_scanned, |
| 422 | unsigned long nr_eligible) |
| 423 | { |
| 424 | struct shrinker *shrinker; |
| 425 | unsigned long freed = 0; |
| 426 | |
| 427 | if (memcg && (!memcg_kmem_enabled() || !mem_cgroup_online(memcg))) |
| 428 | return 0; |
| 429 | |
| 430 | if (nr_scanned == 0) |
| 431 | nr_scanned = SWAP_CLUSTER_MAX; |
| 432 | |
| 433 | if (!down_read_trylock(&shrinker_rwsem)) { |
| 434 | /* |
| 435 | * If we would return 0, our callers would understand that we |
| 436 | * have nothing else to shrink and give up trying. By returning |
| 437 | * 1 we keep it going and assume we'll be able to shrink next |
| 438 | * time. |
| 439 | */ |
| 440 | freed = 1; |
| 441 | goto out; |
| 442 | } |
| 443 | |
| 444 | list_for_each_entry(shrinker, &shrinker_list, list) { |
| 445 | struct shrink_control sc = { |
| 446 | .gfp_mask = gfp_mask, |
| 447 | .nid = nid, |
| 448 | .memcg = memcg, |
| 449 | }; |
| 450 | |
| 451 | /* |
| 452 | * If kernel memory accounting is disabled, we ignore |
| 453 | * SHRINKER_MEMCG_AWARE flag and call all shrinkers |
| 454 | * passing NULL for memcg. |
| 455 | */ |
| 456 | if (memcg_kmem_enabled() && |
| 457 | !!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE)) |
| 458 | continue; |
| 459 | |
| 460 | if (!(shrinker->flags & SHRINKER_NUMA_AWARE)) |
| 461 | sc.nid = 0; |
| 462 | |
| 463 | freed += do_shrink_slab(&sc, shrinker, nr_scanned, nr_eligible); |
| 464 | } |
| 465 | |
| 466 | up_read(&shrinker_rwsem); |
| 467 | out: |
| 468 | cond_resched(); |
| 469 | return freed; |
| 470 | } |
| 471 | |
| 472 | void drop_slab_node(int nid) |
| 473 | { |
| 474 | unsigned long freed; |
| 475 | |
| 476 | do { |
| 477 | struct mem_cgroup *memcg = NULL; |
| 478 | |
| 479 | freed = 0; |
| 480 | do { |
| 481 | freed += shrink_slab(GFP_KERNEL, nid, memcg, |
| 482 | 1000, 1000); |
| 483 | } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); |
| 484 | } while (freed > 10); |
| 485 | } |
| 486 | |
| 487 | void drop_slab(void) |
| 488 | { |
| 489 | int nid; |
| 490 | |
| 491 | for_each_online_node(nid) |
| 492 | drop_slab_node(nid); |
| 493 | } |
| 494 | |
| 495 | static inline int is_page_cache_freeable(struct page *page) |
| 496 | { |
| 497 | /* |
| 498 | * A freeable page cache page is referenced only by the caller |
| 499 | * that isolated the page, the page cache radix tree and |
| 500 | * optional buffer heads at page->private. |
| 501 | */ |
| 502 | return page_count(page) - page_has_private(page) == 2; |
| 503 | } |
| 504 | |
| 505 | static int may_write_to_inode(struct inode *inode, struct scan_control *sc) |
| 506 | { |
| 507 | if (current->flags & PF_SWAPWRITE) |
| 508 | return 1; |
| 509 | if (!inode_write_congested(inode)) |
| 510 | return 1; |
| 511 | if (inode_to_bdi(inode) == current->backing_dev_info) |
| 512 | return 1; |
| 513 | return 0; |
| 514 | } |
| 515 | |
| 516 | /* |
| 517 | * We detected a synchronous write error writing a page out. Probably |
| 518 | * -ENOSPC. We need to propagate that into the address_space for a subsequent |
| 519 | * fsync(), msync() or close(). |
| 520 | * |
| 521 | * The tricky part is that after writepage we cannot touch the mapping: nothing |
| 522 | * prevents it from being freed up. But we have a ref on the page and once |
| 523 | * that page is locked, the mapping is pinned. |
| 524 | * |
| 525 | * We're allowed to run sleeping lock_page() here because we know the caller has |
| 526 | * __GFP_FS. |
| 527 | */ |
| 528 | static void handle_write_error(struct address_space *mapping, |
| 529 | struct page *page, int error) |
| 530 | { |
| 531 | lock_page(page); |
| 532 | if (page_mapping(page) == mapping) |
| 533 | mapping_set_error(mapping, error); |
| 534 | unlock_page(page); |
| 535 | } |
| 536 | |
| 537 | /* possible outcome of pageout() */ |
| 538 | typedef enum { |
| 539 | /* failed to write page out, page is locked */ |
| 540 | PAGE_KEEP, |
| 541 | /* move page to the active list, page is locked */ |
| 542 | PAGE_ACTIVATE, |
| 543 | /* page has been sent to the disk successfully, page is unlocked */ |
| 544 | PAGE_SUCCESS, |
| 545 | /* page is clean and locked */ |
| 546 | PAGE_CLEAN, |
| 547 | } pageout_t; |
| 548 | |
| 549 | /* |
| 550 | * pageout is called by shrink_page_list() for each dirty page. |
| 551 | * Calls ->writepage(). |
| 552 | */ |
| 553 | static pageout_t pageout(struct page *page, struct address_space *mapping, |
| 554 | struct scan_control *sc) |
| 555 | { |
| 556 | /* |
| 557 | * If the page is dirty, only perform writeback if that write |
| 558 | * will be non-blocking. To prevent this allocation from being |
| 559 | * stalled by pagecache activity. But note that there may be |
| 560 | * stalls if we need to run get_block(). We could test |
| 561 | * PagePrivate for that. |
| 562 | * |
| 563 | * If this process is currently in __generic_file_write_iter() against |
| 564 | * this page's queue, we can perform writeback even if that |
| 565 | * will block. |
| 566 | * |
| 567 | * If the page is swapcache, write it back even if that would |
| 568 | * block, for some throttling. This happens by accident, because |
| 569 | * swap_backing_dev_info is bust: it doesn't reflect the |
| 570 | * congestion state of the swapdevs. Easy to fix, if needed. |
| 571 | */ |
| 572 | if (!is_page_cache_freeable(page)) |
| 573 | return PAGE_KEEP; |
| 574 | if (!mapping) { |
| 575 | /* |
| 576 | * Some data journaling orphaned pages can have |
| 577 | * page->mapping == NULL while being dirty with clean buffers. |
| 578 | */ |
| 579 | if (page_has_private(page)) { |
| 580 | if (try_to_free_buffers(page)) { |
| 581 | ClearPageDirty(page); |
| 582 | pr_info("%s: orphaned page\n", __func__); |
| 583 | return PAGE_CLEAN; |
| 584 | } |
| 585 | } |
| 586 | return PAGE_KEEP; |
| 587 | } |
| 588 | if (mapping->a_ops->writepage == NULL) |
| 589 | return PAGE_ACTIVATE; |
| 590 | if (!may_write_to_inode(mapping->host, sc)) |
| 591 | return PAGE_KEEP; |
| 592 | |
| 593 | if (clear_page_dirty_for_io(page)) { |
| 594 | int res; |
| 595 | struct writeback_control wbc = { |
| 596 | .sync_mode = WB_SYNC_NONE, |
| 597 | .nr_to_write = SWAP_CLUSTER_MAX, |
| 598 | .range_start = 0, |
| 599 | .range_end = LLONG_MAX, |
| 600 | .for_reclaim = 1, |
| 601 | }; |
| 602 | |
| 603 | SetPageReclaim(page); |
| 604 | res = mapping->a_ops->writepage(page, &wbc); |
| 605 | if (res < 0) |
| 606 | handle_write_error(mapping, page, res); |
| 607 | if (res == AOP_WRITEPAGE_ACTIVATE) { |
| 608 | ClearPageReclaim(page); |
| 609 | return PAGE_ACTIVATE; |
| 610 | } |
| 611 | |
| 612 | if (!PageWriteback(page)) { |
| 613 | /* synchronous write or broken a_ops? */ |
| 614 | ClearPageReclaim(page); |
| 615 | } |
| 616 | trace_mm_vmscan_writepage(page); |
| 617 | inc_node_page_state(page, NR_VMSCAN_WRITE); |
| 618 | return PAGE_SUCCESS; |
| 619 | } |
| 620 | |
| 621 | return PAGE_CLEAN; |
| 622 | } |
| 623 | |
| 624 | /* |
| 625 | * Same as remove_mapping, but if the page is removed from the mapping, it |
| 626 | * gets returned with a refcount of 0. |
| 627 | */ |
| 628 | static int __remove_mapping(struct address_space *mapping, struct page *page, |
| 629 | bool reclaimed) |
| 630 | { |
| 631 | unsigned long flags; |
| 632 | |
| 633 | BUG_ON(!PageLocked(page)); |
| 634 | BUG_ON(mapping != page_mapping(page)); |
| 635 | |
| 636 | spin_lock_irqsave(&mapping->tree_lock, flags); |
| 637 | /* |
| 638 | * The non racy check for a busy page. |
| 639 | * |
| 640 | * Must be careful with the order of the tests. When someone has |
| 641 | * a ref to the page, it may be possible that they dirty it then |
| 642 | * drop the reference. So if PageDirty is tested before page_count |
| 643 | * here, then the following race may occur: |
| 644 | * |
| 645 | * get_user_pages(&page); |
| 646 | * [user mapping goes away] |
| 647 | * write_to(page); |
| 648 | * !PageDirty(page) [good] |
| 649 | * SetPageDirty(page); |
| 650 | * put_page(page); |
| 651 | * !page_count(page) [good, discard it] |
| 652 | * |
| 653 | * [oops, our write_to data is lost] |
| 654 | * |
| 655 | * Reversing the order of the tests ensures such a situation cannot |
| 656 | * escape unnoticed. The smp_rmb is needed to ensure the page->flags |
| 657 | * load is not satisfied before that of page->_refcount. |
| 658 | * |
| 659 | * Note that if SetPageDirty is always performed via set_page_dirty, |
| 660 | * and thus under tree_lock, then this ordering is not required. |
| 661 | */ |
| 662 | if (!page_ref_freeze(page, 2)) |
| 663 | goto cannot_free; |
| 664 | /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ |
| 665 | if (unlikely(PageDirty(page))) { |
| 666 | page_ref_unfreeze(page, 2); |
| 667 | goto cannot_free; |
| 668 | } |
| 669 | |
| 670 | if (PageSwapCache(page)) { |
| 671 | swp_entry_t swap = { .val = page_private(page) }; |
| 672 | mem_cgroup_swapout(page, swap); |
| 673 | __delete_from_swap_cache(page); |
| 674 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
| 675 | swapcache_free(swap); |
| 676 | } else { |
| 677 | void (*freepage)(struct page *); |
| 678 | void *shadow = NULL; |
| 679 | |
| 680 | freepage = mapping->a_ops->freepage; |
| 681 | /* |
| 682 | * Remember a shadow entry for reclaimed file cache in |
| 683 | * order to detect refaults, thus thrashing, later on. |
| 684 | * |
| 685 | * But don't store shadows in an address space that is |
| 686 | * already exiting. This is not just an optizimation, |
| 687 | * inode reclaim needs to empty out the radix tree or |
| 688 | * the nodes are lost. Don't plant shadows behind its |
| 689 | * back. |
| 690 | * |
| 691 | * We also don't store shadows for DAX mappings because the |
| 692 | * only page cache pages found in these are zero pages |
| 693 | * covering holes, and because we don't want to mix DAX |
| 694 | * exceptional entries and shadow exceptional entries in the |
| 695 | * same page_tree. |
| 696 | */ |
| 697 | if (reclaimed && page_is_file_cache(page) && |
| 698 | !mapping_exiting(mapping) && !dax_mapping(mapping)) |
| 699 | shadow = workingset_eviction(mapping, page); |
| 700 | __delete_from_page_cache(page, shadow); |
| 701 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
| 702 | |
| 703 | if (freepage != NULL) |
| 704 | freepage(page); |
| 705 | } |
| 706 | |
| 707 | return 1; |
| 708 | |
| 709 | cannot_free: |
| 710 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
| 711 | return 0; |
| 712 | } |
| 713 | |
| 714 | /* |
| 715 | * Attempt to detach a locked page from its ->mapping. If it is dirty or if |
| 716 | * someone else has a ref on the page, abort and return 0. If it was |
| 717 | * successfully detached, return 1. Assumes the caller has a single ref on |
| 718 | * this page. |
| 719 | */ |
| 720 | int remove_mapping(struct address_space *mapping, struct page *page) |
| 721 | { |
| 722 | if (__remove_mapping(mapping, page, false)) { |
| 723 | /* |
| 724 | * Unfreezing the refcount with 1 rather than 2 effectively |
| 725 | * drops the pagecache ref for us without requiring another |
| 726 | * atomic operation. |
| 727 | */ |
| 728 | page_ref_unfreeze(page, 1); |
| 729 | return 1; |
| 730 | } |
| 731 | return 0; |
| 732 | } |
| 733 | |
| 734 | /** |
| 735 | * putback_lru_page - put previously isolated page onto appropriate LRU list |
| 736 | * @page: page to be put back to appropriate lru list |
| 737 | * |
| 738 | * Add previously isolated @page to appropriate LRU list. |
| 739 | * Page may still be unevictable for other reasons. |
| 740 | * |
| 741 | * lru_lock must not be held, interrupts must be enabled. |
| 742 | */ |
| 743 | void putback_lru_page(struct page *page) |
| 744 | { |
| 745 | bool is_unevictable; |
| 746 | int was_unevictable = PageUnevictable(page); |
| 747 | |
| 748 | VM_BUG_ON_PAGE(PageLRU(page), page); |
| 749 | |
| 750 | redo: |
| 751 | ClearPageUnevictable(page); |
| 752 | |
| 753 | if (page_evictable(page)) { |
| 754 | /* |
| 755 | * For evictable pages, we can use the cache. |
| 756 | * In event of a race, worst case is we end up with an |
| 757 | * unevictable page on [in]active list. |
| 758 | * We know how to handle that. |
| 759 | */ |
| 760 | is_unevictable = false; |
| 761 | lru_cache_add(page); |
| 762 | } else { |
| 763 | /* |
| 764 | * Put unevictable pages directly on zone's unevictable |
| 765 | * list. |
| 766 | */ |
| 767 | is_unevictable = true; |
| 768 | add_page_to_unevictable_list(page); |
| 769 | /* |
| 770 | * When racing with an mlock or AS_UNEVICTABLE clearing |
| 771 | * (page is unlocked) make sure that if the other thread |
| 772 | * does not observe our setting of PG_lru and fails |
| 773 | * isolation/check_move_unevictable_pages, |
| 774 | * we see PG_mlocked/AS_UNEVICTABLE cleared below and move |
| 775 | * the page back to the evictable list. |
| 776 | * |
| 777 | * The other side is TestClearPageMlocked() or shmem_lock(). |
| 778 | */ |
| 779 | smp_mb(); |
| 780 | } |
| 781 | |
| 782 | /* |
| 783 | * page's status can change while we move it among lru. If an evictable |
| 784 | * page is on unevictable list, it never be freed. To avoid that, |
| 785 | * check after we added it to the list, again. |
| 786 | */ |
| 787 | if (is_unevictable && page_evictable(page)) { |
| 788 | if (!isolate_lru_page(page)) { |
| 789 | put_page(page); |
| 790 | goto redo; |
| 791 | } |
| 792 | /* This means someone else dropped this page from LRU |
| 793 | * So, it will be freed or putback to LRU again. There is |
| 794 | * nothing to do here. |
| 795 | */ |
| 796 | } |
| 797 | |
| 798 | if (was_unevictable && !is_unevictable) |
| 799 | count_vm_event(UNEVICTABLE_PGRESCUED); |
| 800 | else if (!was_unevictable && is_unevictable) |
| 801 | count_vm_event(UNEVICTABLE_PGCULLED); |
| 802 | |
| 803 | put_page(page); /* drop ref from isolate */ |
| 804 | } |
| 805 | |
| 806 | enum page_references { |
| 807 | PAGEREF_RECLAIM, |
| 808 | PAGEREF_RECLAIM_CLEAN, |
| 809 | PAGEREF_KEEP, |
| 810 | PAGEREF_ACTIVATE, |
| 811 | }; |
| 812 | |
| 813 | static enum page_references page_check_references(struct page *page, |
| 814 | struct scan_control *sc) |
| 815 | { |
| 816 | int referenced_ptes, referenced_page; |
| 817 | unsigned long vm_flags; |
| 818 | |
| 819 | referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup, |
| 820 | &vm_flags); |
| 821 | referenced_page = TestClearPageReferenced(page); |
| 822 | |
| 823 | /* |
| 824 | * Mlock lost the isolation race with us. Let try_to_unmap() |
| 825 | * move the page to the unevictable list. |
| 826 | */ |
| 827 | if (vm_flags & VM_LOCKED) |
| 828 | return PAGEREF_RECLAIM; |
| 829 | |
| 830 | if (referenced_ptes) { |
| 831 | if (PageSwapBacked(page)) |
| 832 | return PAGEREF_ACTIVATE; |
| 833 | /* |
| 834 | * All mapped pages start out with page table |
| 835 | * references from the instantiating fault, so we need |
| 836 | * to look twice if a mapped file page is used more |
| 837 | * than once. |
| 838 | * |
| 839 | * Mark it and spare it for another trip around the |
| 840 | * inactive list. Another page table reference will |
| 841 | * lead to its activation. |
| 842 | * |
| 843 | * Note: the mark is set for activated pages as well |
| 844 | * so that recently deactivated but used pages are |
| 845 | * quickly recovered. |
| 846 | */ |
| 847 | SetPageReferenced(page); |
| 848 | |
| 849 | if (referenced_page || referenced_ptes > 1) |
| 850 | return PAGEREF_ACTIVATE; |
| 851 | |
| 852 | /* |
| 853 | * Activate file-backed executable pages after first usage. |
| 854 | */ |
| 855 | if (vm_flags & VM_EXEC) |
| 856 | return PAGEREF_ACTIVATE; |
| 857 | |
| 858 | return PAGEREF_KEEP; |
| 859 | } |
| 860 | |
| 861 | /* Reclaim if clean, defer dirty pages to writeback */ |
| 862 | if (referenced_page && !PageSwapBacked(page)) |
| 863 | return PAGEREF_RECLAIM_CLEAN; |
| 864 | |
| 865 | return PAGEREF_RECLAIM; |
| 866 | } |
| 867 | |
| 868 | /* Check if a page is dirty or under writeback */ |
| 869 | static void page_check_dirty_writeback(struct page *page, |
| 870 | bool *dirty, bool *writeback) |
| 871 | { |
| 872 | struct address_space *mapping; |
| 873 | |
| 874 | /* |
| 875 | * Anonymous pages are not handled by flushers and must be written |
| 876 | * from reclaim context. Do not stall reclaim based on them |
| 877 | */ |
| 878 | if (!page_is_file_cache(page)) { |
| 879 | *dirty = false; |
| 880 | *writeback = false; |
| 881 | return; |
| 882 | } |
| 883 | |
| 884 | /* By default assume that the page flags are accurate */ |
| 885 | *dirty = PageDirty(page); |
| 886 | *writeback = PageWriteback(page); |
| 887 | |
| 888 | /* Verify dirty/writeback state if the filesystem supports it */ |
| 889 | if (!page_has_private(page)) |
| 890 | return; |
| 891 | |
| 892 | mapping = page_mapping(page); |
| 893 | if (mapping && mapping->a_ops->is_dirty_writeback) |
| 894 | mapping->a_ops->is_dirty_writeback(page, dirty, writeback); |
| 895 | } |
| 896 | |
| 897 | /* |
| 898 | * shrink_page_list() returns the number of reclaimed pages |
| 899 | */ |
| 900 | static unsigned long shrink_page_list(struct list_head *page_list, |
| 901 | struct pglist_data *pgdat, |
| 902 | struct scan_control *sc, |
| 903 | enum ttu_flags ttu_flags, |
| 904 | unsigned long *ret_nr_dirty, |
| 905 | unsigned long *ret_nr_unqueued_dirty, |
| 906 | unsigned long *ret_nr_congested, |
| 907 | unsigned long *ret_nr_writeback, |
| 908 | unsigned long *ret_nr_immediate, |
| 909 | bool force_reclaim) |
| 910 | { |
| 911 | LIST_HEAD(ret_pages); |
| 912 | LIST_HEAD(free_pages); |
| 913 | int pgactivate = 0; |
| 914 | unsigned long nr_unqueued_dirty = 0; |
| 915 | unsigned long nr_dirty = 0; |
| 916 | unsigned long nr_congested = 0; |
| 917 | unsigned long nr_reclaimed = 0; |
| 918 | unsigned long nr_writeback = 0; |
| 919 | unsigned long nr_immediate = 0; |
| 920 | |
| 921 | cond_resched(); |
| 922 | |
| 923 | while (!list_empty(page_list)) { |
| 924 | struct address_space *mapping; |
| 925 | struct page *page; |
| 926 | int may_enter_fs; |
| 927 | enum page_references references = PAGEREF_RECLAIM_CLEAN; |
| 928 | bool dirty, writeback; |
| 929 | bool lazyfree = false; |
| 930 | int ret = SWAP_SUCCESS; |
| 931 | |
| 932 | cond_resched(); |
| 933 | |
| 934 | page = lru_to_page(page_list); |
| 935 | list_del(&page->lru); |
| 936 | |
| 937 | if (!trylock_page(page)) |
| 938 | goto keep; |
| 939 | |
| 940 | VM_BUG_ON_PAGE(PageActive(page), page); |
| 941 | |
| 942 | sc->nr_scanned++; |
| 943 | |
| 944 | if (unlikely(!page_evictable(page))) |
| 945 | goto cull_mlocked; |
| 946 | |
| 947 | if (!sc->may_unmap && page_mapped(page)) |
| 948 | goto keep_locked; |
| 949 | |
| 950 | /* Double the slab pressure for mapped and swapcache pages */ |
| 951 | if (page_mapped(page) || PageSwapCache(page)) |
| 952 | sc->nr_scanned++; |
| 953 | |
| 954 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || |
| 955 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); |
| 956 | |
| 957 | /* |
| 958 | * The number of dirty pages determines if a zone is marked |
| 959 | * reclaim_congested which affects wait_iff_congested. kswapd |
| 960 | * will stall and start writing pages if the tail of the LRU |
| 961 | * is all dirty unqueued pages. |
| 962 | */ |
| 963 | page_check_dirty_writeback(page, &dirty, &writeback); |
| 964 | if (dirty || writeback) |
| 965 | nr_dirty++; |
| 966 | |
| 967 | if (dirty && !writeback) |
| 968 | nr_unqueued_dirty++; |
| 969 | |
| 970 | /* |
| 971 | * Treat this page as congested if the underlying BDI is or if |
| 972 | * pages are cycling through the LRU so quickly that the |
| 973 | * pages marked for immediate reclaim are making it to the |
| 974 | * end of the LRU a second time. |
| 975 | */ |
| 976 | mapping = page_mapping(page); |
| 977 | if (((dirty || writeback) && mapping && |
| 978 | inode_write_congested(mapping->host)) || |
| 979 | (writeback && PageReclaim(page))) |
| 980 | nr_congested++; |
| 981 | |
| 982 | /* |
| 983 | * If a page at the tail of the LRU is under writeback, there |
| 984 | * are three cases to consider. |
| 985 | * |
| 986 | * 1) If reclaim is encountering an excessive number of pages |
| 987 | * under writeback and this page is both under writeback and |
| 988 | * PageReclaim then it indicates that pages are being queued |
| 989 | * for IO but are being recycled through the LRU before the |
| 990 | * IO can complete. Waiting on the page itself risks an |
| 991 | * indefinite stall if it is impossible to writeback the |
| 992 | * page due to IO error or disconnected storage so instead |
| 993 | * note that the LRU is being scanned too quickly and the |
| 994 | * caller can stall after page list has been processed. |
| 995 | * |
| 996 | * 2) Global or new memcg reclaim encounters a page that is |
| 997 | * not marked for immediate reclaim, or the caller does not |
| 998 | * have __GFP_FS (or __GFP_IO if it's simply going to swap, |
| 999 | * not to fs). In this case mark the page for immediate |
| 1000 | * reclaim and continue scanning. |
| 1001 | * |
| 1002 | * Require may_enter_fs because we would wait on fs, which |
| 1003 | * may not have submitted IO yet. And the loop driver might |
| 1004 | * enter reclaim, and deadlock if it waits on a page for |
| 1005 | * which it is needed to do the write (loop masks off |
| 1006 | * __GFP_IO|__GFP_FS for this reason); but more thought |
| 1007 | * would probably show more reasons. |
| 1008 | * |
| 1009 | * 3) Legacy memcg encounters a page that is already marked |
| 1010 | * PageReclaim. memcg does not have any dirty pages |
| 1011 | * throttling so we could easily OOM just because too many |
| 1012 | * pages are in writeback and there is nothing else to |
| 1013 | * reclaim. Wait for the writeback to complete. |
| 1014 | */ |
| 1015 | if (PageWriteback(page)) { |
| 1016 | /* Case 1 above */ |
| 1017 | if (current_is_kswapd() && |
| 1018 | PageReclaim(page) && |
| 1019 | test_bit(PGDAT_WRITEBACK, &pgdat->flags)) { |
| 1020 | nr_immediate++; |
| 1021 | goto keep_locked; |
| 1022 | |
| 1023 | /* Case 2 above */ |
| 1024 | } else if (sane_reclaim(sc) || |
| 1025 | !PageReclaim(page) || !may_enter_fs) { |
| 1026 | /* |
| 1027 | * This is slightly racy - end_page_writeback() |
| 1028 | * might have just cleared PageReclaim, then |
| 1029 | * setting PageReclaim here end up interpreted |
| 1030 | * as PageReadahead - but that does not matter |
| 1031 | * enough to care. What we do want is for this |
| 1032 | * page to have PageReclaim set next time memcg |
| 1033 | * reclaim reaches the tests above, so it will |
| 1034 | * then wait_on_page_writeback() to avoid OOM; |
| 1035 | * and it's also appropriate in global reclaim. |
| 1036 | */ |
| 1037 | SetPageReclaim(page); |
| 1038 | nr_writeback++; |
| 1039 | goto keep_locked; |
| 1040 | |
| 1041 | /* Case 3 above */ |
| 1042 | } else { |
| 1043 | unlock_page(page); |
| 1044 | wait_on_page_writeback(page); |
| 1045 | /* then go back and try same page again */ |
| 1046 | list_add_tail(&page->lru, page_list); |
| 1047 | continue; |
| 1048 | } |
| 1049 | } |
| 1050 | |
| 1051 | if (!force_reclaim) |
| 1052 | references = page_check_references(page, sc); |
| 1053 | |
| 1054 | switch (references) { |
| 1055 | case PAGEREF_ACTIVATE: |
| 1056 | goto activate_locked; |
| 1057 | case PAGEREF_KEEP: |
| 1058 | goto keep_locked; |
| 1059 | case PAGEREF_RECLAIM: |
| 1060 | case PAGEREF_RECLAIM_CLEAN: |
| 1061 | ; /* try to reclaim the page below */ |
| 1062 | } |
| 1063 | |
| 1064 | /* |
| 1065 | * Anonymous process memory has backing store? |
| 1066 | * Try to allocate it some swap space here. |
| 1067 | */ |
| 1068 | if (PageAnon(page) && !PageSwapCache(page)) { |
| 1069 | if (!(sc->gfp_mask & __GFP_IO)) |
| 1070 | goto keep_locked; |
| 1071 | if (!add_to_swap(page, page_list)) |
| 1072 | goto activate_locked; |
| 1073 | lazyfree = true; |
| 1074 | may_enter_fs = 1; |
| 1075 | |
| 1076 | /* Adding to swap updated mapping */ |
| 1077 | mapping = page_mapping(page); |
| 1078 | } else if (unlikely(PageTransHuge(page))) { |
| 1079 | /* Split file THP */ |
| 1080 | if (split_huge_page_to_list(page, page_list)) |
| 1081 | goto keep_locked; |
| 1082 | } |
| 1083 | |
| 1084 | VM_BUG_ON_PAGE(PageTransHuge(page), page); |
| 1085 | |
| 1086 | /* |
| 1087 | * The page is mapped into the page tables of one or more |
| 1088 | * processes. Try to unmap it here. |
| 1089 | */ |
| 1090 | if (page_mapped(page) && mapping) { |
| 1091 | switch (ret = try_to_unmap(page, lazyfree ? |
| 1092 | (ttu_flags | TTU_BATCH_FLUSH | TTU_LZFREE) : |
| 1093 | (ttu_flags | TTU_BATCH_FLUSH))) { |
| 1094 | case SWAP_FAIL: |
| 1095 | goto activate_locked; |
| 1096 | case SWAP_AGAIN: |
| 1097 | goto keep_locked; |
| 1098 | case SWAP_MLOCK: |
| 1099 | goto cull_mlocked; |
| 1100 | case SWAP_LZFREE: |
| 1101 | goto lazyfree; |
| 1102 | case SWAP_SUCCESS: |
| 1103 | ; /* try to free the page below */ |
| 1104 | } |
| 1105 | } |
| 1106 | |
| 1107 | if (PageDirty(page)) { |
| 1108 | /* |
| 1109 | * Only kswapd can writeback filesystem pages to |
| 1110 | * avoid risk of stack overflow but only writeback |
| 1111 | * if many dirty pages have been encountered. |
| 1112 | */ |
| 1113 | if (page_is_file_cache(page) && |
| 1114 | (!current_is_kswapd() || |
| 1115 | !test_bit(PGDAT_DIRTY, &pgdat->flags))) { |
| 1116 | /* |
| 1117 | * Immediately reclaim when written back. |
| 1118 | * Similar in principal to deactivate_page() |
| 1119 | * except we already have the page isolated |
| 1120 | * and know it's dirty |
| 1121 | */ |
| 1122 | inc_node_page_state(page, NR_VMSCAN_IMMEDIATE); |
| 1123 | SetPageReclaim(page); |
| 1124 | |
| 1125 | goto keep_locked; |
| 1126 | } |
| 1127 | |
| 1128 | if (references == PAGEREF_RECLAIM_CLEAN) |
| 1129 | goto keep_locked; |
| 1130 | if (!may_enter_fs) |
| 1131 | goto keep_locked; |
| 1132 | if (!sc->may_writepage) |
| 1133 | goto keep_locked; |
| 1134 | |
| 1135 | /* |
| 1136 | * Page is dirty. Flush the TLB if a writable entry |
| 1137 | * potentially exists to avoid CPU writes after IO |
| 1138 | * starts and then write it out here. |
| 1139 | */ |
| 1140 | try_to_unmap_flush_dirty(); |
| 1141 | switch (pageout(page, mapping, sc)) { |
| 1142 | case PAGE_KEEP: |
| 1143 | goto keep_locked; |
| 1144 | case PAGE_ACTIVATE: |
| 1145 | goto activate_locked; |
| 1146 | case PAGE_SUCCESS: |
| 1147 | if (PageWriteback(page)) |
| 1148 | goto keep; |
| 1149 | if (PageDirty(page)) |
| 1150 | goto keep; |
| 1151 | |
| 1152 | /* |
| 1153 | * A synchronous write - probably a ramdisk. Go |
| 1154 | * ahead and try to reclaim the page. |
| 1155 | */ |
| 1156 | if (!trylock_page(page)) |
| 1157 | goto keep; |
| 1158 | if (PageDirty(page) || PageWriteback(page)) |
| 1159 | goto keep_locked; |
| 1160 | mapping = page_mapping(page); |
| 1161 | case PAGE_CLEAN: |
| 1162 | ; /* try to free the page below */ |
| 1163 | } |
| 1164 | } |
| 1165 | |
| 1166 | /* |
| 1167 | * If the page has buffers, try to free the buffer mappings |
| 1168 | * associated with this page. If we succeed we try to free |
| 1169 | * the page as well. |
| 1170 | * |
| 1171 | * We do this even if the page is PageDirty(). |
| 1172 | * try_to_release_page() does not perform I/O, but it is |
| 1173 | * possible for a page to have PageDirty set, but it is actually |
| 1174 | * clean (all its buffers are clean). This happens if the |
| 1175 | * buffers were written out directly, with submit_bh(). ext3 |
| 1176 | * will do this, as well as the blockdev mapping. |
| 1177 | * try_to_release_page() will discover that cleanness and will |
| 1178 | * drop the buffers and mark the page clean - it can be freed. |
| 1179 | * |
| 1180 | * Rarely, pages can have buffers and no ->mapping. These are |
| 1181 | * the pages which were not successfully invalidated in |
| 1182 | * truncate_complete_page(). We try to drop those buffers here |
| 1183 | * and if that worked, and the page is no longer mapped into |
| 1184 | * process address space (page_count == 1) it can be freed. |
| 1185 | * Otherwise, leave the page on the LRU so it is swappable. |
| 1186 | */ |
| 1187 | if (page_has_private(page)) { |
| 1188 | if (!try_to_release_page(page, sc->gfp_mask)) |
| 1189 | goto activate_locked; |
| 1190 | if (!mapping && page_count(page) == 1) { |
| 1191 | unlock_page(page); |
| 1192 | if (put_page_testzero(page)) |
| 1193 | goto free_it; |
| 1194 | else { |
| 1195 | /* |
| 1196 | * rare race with speculative reference. |
| 1197 | * the speculative reference will free |
| 1198 | * this page shortly, so we may |
| 1199 | * increment nr_reclaimed here (and |
| 1200 | * leave it off the LRU). |
| 1201 | */ |
| 1202 | nr_reclaimed++; |
| 1203 | continue; |
| 1204 | } |
| 1205 | } |
| 1206 | } |
| 1207 | |
| 1208 | lazyfree: |
| 1209 | if (!mapping || !__remove_mapping(mapping, page, true)) |
| 1210 | goto keep_locked; |
| 1211 | |
| 1212 | /* |
| 1213 | * At this point, we have no other references and there is |
| 1214 | * no way to pick any more up (removed from LRU, removed |
| 1215 | * from pagecache). Can use non-atomic bitops now (and |
| 1216 | * we obviously don't have to worry about waking up a process |
| 1217 | * waiting on the page lock, because there are no references. |
| 1218 | */ |
| 1219 | __ClearPageLocked(page); |
| 1220 | free_it: |
| 1221 | if (ret == SWAP_LZFREE) |
| 1222 | count_vm_event(PGLAZYFREED); |
| 1223 | |
| 1224 | nr_reclaimed++; |
| 1225 | |
| 1226 | /* |
| 1227 | * Is there need to periodically free_page_list? It would |
| 1228 | * appear not as the counts should be low |
| 1229 | */ |
| 1230 | list_add(&page->lru, &free_pages); |
| 1231 | continue; |
| 1232 | |
| 1233 | cull_mlocked: |
| 1234 | if (PageSwapCache(page)) |
| 1235 | try_to_free_swap(page); |
| 1236 | unlock_page(page); |
| 1237 | list_add(&page->lru, &ret_pages); |
| 1238 | continue; |
| 1239 | |
| 1240 | activate_locked: |
| 1241 | /* Not a candidate for swapping, so reclaim swap space. */ |
| 1242 | if (PageSwapCache(page) && mem_cgroup_swap_full(page)) |
| 1243 | try_to_free_swap(page); |
| 1244 | VM_BUG_ON_PAGE(PageActive(page), page); |
| 1245 | SetPageActive(page); |
| 1246 | pgactivate++; |
| 1247 | keep_locked: |
| 1248 | unlock_page(page); |
| 1249 | keep: |
| 1250 | list_add(&page->lru, &ret_pages); |
| 1251 | VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page); |
| 1252 | } |
| 1253 | |
| 1254 | mem_cgroup_uncharge_list(&free_pages); |
| 1255 | try_to_unmap_flush(); |
| 1256 | free_hot_cold_page_list(&free_pages, true); |
| 1257 | |
| 1258 | list_splice(&ret_pages, page_list); |
| 1259 | count_vm_events(PGACTIVATE, pgactivate); |
| 1260 | |
| 1261 | *ret_nr_dirty += nr_dirty; |
| 1262 | *ret_nr_congested += nr_congested; |
| 1263 | *ret_nr_unqueued_dirty += nr_unqueued_dirty; |
| 1264 | *ret_nr_writeback += nr_writeback; |
| 1265 | *ret_nr_immediate += nr_immediate; |
| 1266 | return nr_reclaimed; |
| 1267 | } |
| 1268 | |
| 1269 | unsigned long reclaim_clean_pages_from_list(struct zone *zone, |
| 1270 | struct list_head *page_list) |
| 1271 | { |
| 1272 | struct scan_control sc = { |
| 1273 | .gfp_mask = GFP_KERNEL, |
| 1274 | .priority = DEF_PRIORITY, |
| 1275 | .may_unmap = 1, |
| 1276 | }; |
| 1277 | unsigned long ret, dummy1, dummy2, dummy3, dummy4, dummy5; |
| 1278 | struct page *page, *next; |
| 1279 | LIST_HEAD(clean_pages); |
| 1280 | |
| 1281 | list_for_each_entry_safe(page, next, page_list, lru) { |
| 1282 | if (page_is_file_cache(page) && !PageDirty(page) && |
| 1283 | !__PageMovable(page)) { |
| 1284 | ClearPageActive(page); |
| 1285 | list_move(&page->lru, &clean_pages); |
| 1286 | } |
| 1287 | } |
| 1288 | |
| 1289 | ret = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc, |
| 1290 | TTU_UNMAP|TTU_IGNORE_ACCESS, |
| 1291 | &dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true); |
| 1292 | list_splice(&clean_pages, page_list); |
| 1293 | mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -ret); |
| 1294 | return ret; |
| 1295 | } |
| 1296 | |
| 1297 | /* |
| 1298 | * Attempt to remove the specified page from its LRU. Only take this page |
| 1299 | * if it is of the appropriate PageActive status. Pages which are being |
| 1300 | * freed elsewhere are also ignored. |
| 1301 | * |
| 1302 | * page: page to consider |
| 1303 | * mode: one of the LRU isolation modes defined above |
| 1304 | * |
| 1305 | * returns 0 on success, -ve errno on failure. |
| 1306 | */ |
| 1307 | int __isolate_lru_page(struct page *page, isolate_mode_t mode) |
| 1308 | { |
| 1309 | int ret = -EINVAL; |
| 1310 | |
| 1311 | /* Only take pages on the LRU. */ |
| 1312 | if (!PageLRU(page)) |
| 1313 | return ret; |
| 1314 | |
| 1315 | /* Compaction should not handle unevictable pages but CMA can do so */ |
| 1316 | if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE)) |
| 1317 | return ret; |
| 1318 | |
| 1319 | ret = -EBUSY; |
| 1320 | |
| 1321 | /* |
| 1322 | * To minimise LRU disruption, the caller can indicate that it only |
| 1323 | * wants to isolate pages it will be able to operate on without |
| 1324 | * blocking - clean pages for the most part. |
| 1325 | * |
| 1326 | * ISOLATE_CLEAN means that only clean pages should be isolated. This |
| 1327 | * is used by reclaim when it is cannot write to backing storage |
| 1328 | * |
| 1329 | * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages |
| 1330 | * that it is possible to migrate without blocking |
| 1331 | */ |
| 1332 | if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) { |
| 1333 | /* All the caller can do on PageWriteback is block */ |
| 1334 | if (PageWriteback(page)) |
| 1335 | return ret; |
| 1336 | |
| 1337 | if (PageDirty(page)) { |
| 1338 | struct address_space *mapping; |
| 1339 | |
| 1340 | /* ISOLATE_CLEAN means only clean pages */ |
| 1341 | if (mode & ISOLATE_CLEAN) |
| 1342 | return ret; |
| 1343 | |
| 1344 | /* |
| 1345 | * Only pages without mappings or that have a |
| 1346 | * ->migratepage callback are possible to migrate |
| 1347 | * without blocking |
| 1348 | */ |
| 1349 | mapping = page_mapping(page); |
| 1350 | if (mapping && !mapping->a_ops->migratepage) |
| 1351 | return ret; |
| 1352 | } |
| 1353 | } |
| 1354 | |
| 1355 | if ((mode & ISOLATE_UNMAPPED) && page_mapped(page)) |
| 1356 | return ret; |
| 1357 | |
| 1358 | if (likely(get_page_unless_zero(page))) { |
| 1359 | /* |
| 1360 | * Be careful not to clear PageLRU until after we're |
| 1361 | * sure the page is not being freed elsewhere -- the |
| 1362 | * page release code relies on it. |
| 1363 | */ |
| 1364 | ClearPageLRU(page); |
| 1365 | ret = 0; |
| 1366 | } |
| 1367 | |
| 1368 | return ret; |
| 1369 | } |
| 1370 | |
| 1371 | |
| 1372 | /* |
| 1373 | * Update LRU sizes after isolating pages. The LRU size updates must |
| 1374 | * be complete before mem_cgroup_update_lru_size due to a santity check. |
| 1375 | */ |
| 1376 | static __always_inline void update_lru_sizes(struct lruvec *lruvec, |
| 1377 | enum lru_list lru, unsigned long *nr_zone_taken, |
| 1378 | unsigned long nr_taken) |
| 1379 | { |
| 1380 | int zid; |
| 1381 | |
| 1382 | for (zid = 0; zid < MAX_NR_ZONES; zid++) { |
| 1383 | if (!nr_zone_taken[zid]) |
| 1384 | continue; |
| 1385 | |
| 1386 | __update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]); |
| 1387 | } |
| 1388 | |
| 1389 | #ifdef CONFIG_MEMCG |
| 1390 | mem_cgroup_update_lru_size(lruvec, lru, -nr_taken); |
| 1391 | #endif |
| 1392 | } |
| 1393 | |
| 1394 | /* |
| 1395 | * zone_lru_lock is heavily contended. Some of the functions that |
| 1396 | * shrink the lists perform better by taking out a batch of pages |
| 1397 | * and working on them outside the LRU lock. |
| 1398 | * |
| 1399 | * For pagecache intensive workloads, this function is the hottest |
| 1400 | * spot in the kernel (apart from copy_*_user functions). |
| 1401 | * |
| 1402 | * Appropriate locks must be held before calling this function. |
| 1403 | * |
| 1404 | * @nr_to_scan: The number of pages to look through on the list. |
| 1405 | * @lruvec: The LRU vector to pull pages from. |
| 1406 | * @dst: The temp list to put pages on to. |
| 1407 | * @nr_scanned: The number of pages that were scanned. |
| 1408 | * @sc: The scan_control struct for this reclaim session |
| 1409 | * @mode: One of the LRU isolation modes |
| 1410 | * @lru: LRU list id for isolating |
| 1411 | * |
| 1412 | * returns how many pages were moved onto *@dst. |
| 1413 | */ |
| 1414 | static unsigned long isolate_lru_pages(unsigned long nr_to_scan, |
| 1415 | struct lruvec *lruvec, struct list_head *dst, |
| 1416 | unsigned long *nr_scanned, struct scan_control *sc, |
| 1417 | isolate_mode_t mode, enum lru_list lru) |
| 1418 | { |
| 1419 | struct list_head *src = &lruvec->lists[lru]; |
| 1420 | unsigned long nr_taken = 0; |
| 1421 | unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 }; |
| 1422 | unsigned long nr_skipped[MAX_NR_ZONES] = { 0, }; |
| 1423 | unsigned long scan, nr_pages; |
| 1424 | LIST_HEAD(pages_skipped); |
| 1425 | |
| 1426 | for (scan = 0; scan < nr_to_scan && nr_taken < nr_to_scan && |
| 1427 | !list_empty(src);) { |
| 1428 | struct page *page; |
| 1429 | |
| 1430 | page = lru_to_page(src); |
| 1431 | prefetchw_prev_lru_page(page, src, flags); |
| 1432 | |
| 1433 | VM_BUG_ON_PAGE(!PageLRU(page), page); |
| 1434 | |
| 1435 | if (page_zonenum(page) > sc->reclaim_idx) { |
| 1436 | list_move(&page->lru, &pages_skipped); |
| 1437 | nr_skipped[page_zonenum(page)]++; |
| 1438 | continue; |
| 1439 | } |
| 1440 | |
| 1441 | /* |
| 1442 | * Account for scanned and skipped separetly to avoid the pgdat |
| 1443 | * being prematurely marked unreclaimable by pgdat_reclaimable. |
| 1444 | */ |
| 1445 | scan++; |
| 1446 | |
| 1447 | switch (__isolate_lru_page(page, mode)) { |
| 1448 | case 0: |
| 1449 | nr_pages = hpage_nr_pages(page); |
| 1450 | nr_taken += nr_pages; |
| 1451 | nr_zone_taken[page_zonenum(page)] += nr_pages; |
| 1452 | list_move(&page->lru, dst); |
| 1453 | break; |
| 1454 | |
| 1455 | case -EBUSY: |
| 1456 | /* else it is being freed elsewhere */ |
| 1457 | list_move(&page->lru, src); |
| 1458 | continue; |
| 1459 | |
| 1460 | default: |
| 1461 | BUG(); |
| 1462 | } |
| 1463 | } |
| 1464 | |
| 1465 | /* |
| 1466 | * Splice any skipped pages to the start of the LRU list. Note that |
| 1467 | * this disrupts the LRU order when reclaiming for lower zones but |
| 1468 | * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX |
| 1469 | * scanning would soon rescan the same pages to skip and put the |
| 1470 | * system at risk of premature OOM. |
| 1471 | */ |
| 1472 | if (!list_empty(&pages_skipped)) { |
| 1473 | int zid; |
| 1474 | unsigned long total_skipped = 0; |
| 1475 | |
| 1476 | for (zid = 0; zid < MAX_NR_ZONES; zid++) { |
| 1477 | if (!nr_skipped[zid]) |
| 1478 | continue; |
| 1479 | |
| 1480 | __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]); |
| 1481 | total_skipped += nr_skipped[zid]; |
| 1482 | } |
| 1483 | |
| 1484 | /* |
| 1485 | * Account skipped pages as a partial scan as the pgdat may be |
| 1486 | * close to unreclaimable. If the LRU list is empty, account |
| 1487 | * skipped pages as a full scan. |
| 1488 | */ |
| 1489 | scan += list_empty(src) ? total_skipped : total_skipped >> 2; |
| 1490 | |
| 1491 | list_splice(&pages_skipped, src); |
| 1492 | } |
| 1493 | *nr_scanned = scan; |
| 1494 | trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, scan, |
| 1495 | nr_taken, mode, is_file_lru(lru)); |
| 1496 | update_lru_sizes(lruvec, lru, nr_zone_taken, nr_taken); |
| 1497 | return nr_taken; |
| 1498 | } |
| 1499 | |
| 1500 | /** |
| 1501 | * isolate_lru_page - tries to isolate a page from its LRU list |
| 1502 | * @page: page to isolate from its LRU list |
| 1503 | * |
| 1504 | * Isolates a @page from an LRU list, clears PageLRU and adjusts the |
| 1505 | * vmstat statistic corresponding to whatever LRU list the page was on. |
| 1506 | * |
| 1507 | * Returns 0 if the page was removed from an LRU list. |
| 1508 | * Returns -EBUSY if the page was not on an LRU list. |
| 1509 | * |
| 1510 | * The returned page will have PageLRU() cleared. If it was found on |
| 1511 | * the active list, it will have PageActive set. If it was found on |
| 1512 | * the unevictable list, it will have the PageUnevictable bit set. That flag |
| 1513 | * may need to be cleared by the caller before letting the page go. |
| 1514 | * |
| 1515 | * The vmstat statistic corresponding to the list on which the page was |
| 1516 | * found will be decremented. |
| 1517 | * |
| 1518 | * Restrictions: |
| 1519 | * (1) Must be called with an elevated refcount on the page. This is a |
| 1520 | * fundamentnal difference from isolate_lru_pages (which is called |
| 1521 | * without a stable reference). |
| 1522 | * (2) the lru_lock must not be held. |
| 1523 | * (3) interrupts must be enabled. |
| 1524 | */ |
| 1525 | int isolate_lru_page(struct page *page) |
| 1526 | { |
| 1527 | int ret = -EBUSY; |
| 1528 | |
| 1529 | VM_BUG_ON_PAGE(!page_count(page), page); |
| 1530 | WARN_RATELIMIT(PageTail(page), "trying to isolate tail page"); |
| 1531 | |
| 1532 | if (PageLRU(page)) { |
| 1533 | struct zone *zone = page_zone(page); |
| 1534 | struct lruvec *lruvec; |
| 1535 | |
| 1536 | spin_lock_irq(zone_lru_lock(zone)); |
| 1537 | lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat); |
| 1538 | if (PageLRU(page)) { |
| 1539 | int lru = page_lru(page); |
| 1540 | get_page(page); |
| 1541 | ClearPageLRU(page); |
| 1542 | del_page_from_lru_list(page, lruvec, lru); |
| 1543 | ret = 0; |
| 1544 | } |
| 1545 | spin_unlock_irq(zone_lru_lock(zone)); |
| 1546 | } |
| 1547 | return ret; |
| 1548 | } |
| 1549 | |
| 1550 | /* |
| 1551 | * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and |
| 1552 | * then get resheduled. When there are massive number of tasks doing page |
| 1553 | * allocation, such sleeping direct reclaimers may keep piling up on each CPU, |
| 1554 | * the LRU list will go small and be scanned faster than necessary, leading to |
| 1555 | * unnecessary swapping, thrashing and OOM. |
| 1556 | */ |
| 1557 | static int too_many_isolated(struct pglist_data *pgdat, int file, |
| 1558 | struct scan_control *sc) |
| 1559 | { |
| 1560 | unsigned long inactive, isolated; |
| 1561 | |
| 1562 | if (current_is_kswapd()) |
| 1563 | return 0; |
| 1564 | |
| 1565 | if (!sane_reclaim(sc)) |
| 1566 | return 0; |
| 1567 | |
| 1568 | if (file) { |
| 1569 | inactive = node_page_state(pgdat, NR_INACTIVE_FILE); |
| 1570 | isolated = node_page_state(pgdat, NR_ISOLATED_FILE); |
| 1571 | } else { |
| 1572 | inactive = node_page_state(pgdat, NR_INACTIVE_ANON); |
| 1573 | isolated = node_page_state(pgdat, NR_ISOLATED_ANON); |
| 1574 | } |
| 1575 | |
| 1576 | /* |
| 1577 | * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they |
| 1578 | * won't get blocked by normal direct-reclaimers, forming a circular |
| 1579 | * deadlock. |
| 1580 | */ |
| 1581 | if ((sc->gfp_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS)) |
| 1582 | inactive >>= 3; |
| 1583 | |
| 1584 | return isolated > inactive; |
| 1585 | } |
| 1586 | |
| 1587 | static noinline_for_stack void |
| 1588 | putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list) |
| 1589 | { |
| 1590 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
| 1591 | struct pglist_data *pgdat = lruvec_pgdat(lruvec); |
| 1592 | LIST_HEAD(pages_to_free); |
| 1593 | |
| 1594 | /* |
| 1595 | * Put back any unfreeable pages. |
| 1596 | */ |
| 1597 | while (!list_empty(page_list)) { |
| 1598 | struct page *page = lru_to_page(page_list); |
| 1599 | int lru; |
| 1600 | |
| 1601 | VM_BUG_ON_PAGE(PageLRU(page), page); |
| 1602 | list_del(&page->lru); |
| 1603 | if (unlikely(!page_evictable(page))) { |
| 1604 | spin_unlock_irq(&pgdat->lru_lock); |
| 1605 | putback_lru_page(page); |
| 1606 | spin_lock_irq(&pgdat->lru_lock); |
| 1607 | continue; |
| 1608 | } |
| 1609 | |
| 1610 | lruvec = mem_cgroup_page_lruvec(page, pgdat); |
| 1611 | |
| 1612 | SetPageLRU(page); |
| 1613 | lru = page_lru(page); |
| 1614 | add_page_to_lru_list(page, lruvec, lru); |
| 1615 | |
| 1616 | if (is_active_lru(lru)) { |
| 1617 | int file = is_file_lru(lru); |
| 1618 | int numpages = hpage_nr_pages(page); |
| 1619 | reclaim_stat->recent_rotated[file] += numpages; |
| 1620 | } |
| 1621 | if (put_page_testzero(page)) { |
| 1622 | __ClearPageLRU(page); |
| 1623 | __ClearPageActive(page); |
| 1624 | del_page_from_lru_list(page, lruvec, lru); |
| 1625 | |
| 1626 | if (unlikely(PageCompound(page))) { |
| 1627 | spin_unlock_irq(&pgdat->lru_lock); |
| 1628 | mem_cgroup_uncharge(page); |
| 1629 | (*get_compound_page_dtor(page))(page); |
| 1630 | spin_lock_irq(&pgdat->lru_lock); |
| 1631 | } else |
| 1632 | list_add(&page->lru, &pages_to_free); |
| 1633 | } |
| 1634 | } |
| 1635 | |
| 1636 | /* |
| 1637 | * To save our caller's stack, now use input list for pages to free. |
| 1638 | */ |
| 1639 | list_splice(&pages_to_free, page_list); |
| 1640 | } |
| 1641 | |
| 1642 | /* |
| 1643 | * If a kernel thread (such as nfsd for loop-back mounts) services |
| 1644 | * a backing device by writing to the page cache it sets PF_LESS_THROTTLE. |
| 1645 | * In that case we should only throttle if the backing device it is |
| 1646 | * writing to is congested. In other cases it is safe to throttle. |
| 1647 | */ |
| 1648 | static int current_may_throttle(void) |
| 1649 | { |
| 1650 | return !(current->flags & PF_LESS_THROTTLE) || |
| 1651 | current->backing_dev_info == NULL || |
| 1652 | bdi_write_congested(current->backing_dev_info); |
| 1653 | } |
| 1654 | |
| 1655 | static bool inactive_reclaimable_pages(struct lruvec *lruvec, |
| 1656 | struct scan_control *sc, enum lru_list lru) |
| 1657 | { |
| 1658 | int zid; |
| 1659 | struct zone *zone; |
| 1660 | int file = is_file_lru(lru); |
| 1661 | struct pglist_data *pgdat = lruvec_pgdat(lruvec); |
| 1662 | |
| 1663 | if (!global_reclaim(sc)) |
| 1664 | return true; |
| 1665 | |
| 1666 | for (zid = sc->reclaim_idx; zid >= 0; zid--) { |
| 1667 | zone = &pgdat->node_zones[zid]; |
| 1668 | if (!managed_zone(zone)) |
| 1669 | continue; |
| 1670 | |
| 1671 | if (zone_page_state_snapshot(zone, NR_ZONE_LRU_BASE + |
| 1672 | LRU_FILE * file) >= SWAP_CLUSTER_MAX) |
| 1673 | return true; |
| 1674 | } |
| 1675 | |
| 1676 | return false; |
| 1677 | } |
| 1678 | |
| 1679 | /* |
| 1680 | * shrink_inactive_list() is a helper for shrink_node(). It returns the number |
| 1681 | * of reclaimed pages |
| 1682 | */ |
| 1683 | static noinline_for_stack unsigned long |
| 1684 | shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, |
| 1685 | struct scan_control *sc, enum lru_list lru) |
| 1686 | { |
| 1687 | LIST_HEAD(page_list); |
| 1688 | unsigned long nr_scanned; |
| 1689 | unsigned long nr_reclaimed = 0; |
| 1690 | unsigned long nr_taken; |
| 1691 | unsigned long nr_dirty = 0; |
| 1692 | unsigned long nr_congested = 0; |
| 1693 | unsigned long nr_unqueued_dirty = 0; |
| 1694 | unsigned long nr_writeback = 0; |
| 1695 | unsigned long nr_immediate = 0; |
| 1696 | isolate_mode_t isolate_mode = 0; |
| 1697 | int file = is_file_lru(lru); |
| 1698 | struct pglist_data *pgdat = lruvec_pgdat(lruvec); |
| 1699 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
| 1700 | |
| 1701 | if (!inactive_reclaimable_pages(lruvec, sc, lru)) |
| 1702 | return 0; |
| 1703 | |
| 1704 | while (unlikely(too_many_isolated(pgdat, file, sc))) { |
| 1705 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
| 1706 | |
| 1707 | /* We are about to die and free our memory. Return now. */ |
| 1708 | if (fatal_signal_pending(current)) |
| 1709 | return SWAP_CLUSTER_MAX; |
| 1710 | } |
| 1711 | |
| 1712 | lru_add_drain(); |
| 1713 | |
| 1714 | if (!sc->may_unmap) |
| 1715 | isolate_mode |= ISOLATE_UNMAPPED; |
| 1716 | if (!sc->may_writepage) |
| 1717 | isolate_mode |= ISOLATE_CLEAN; |
| 1718 | |
| 1719 | spin_lock_irq(&pgdat->lru_lock); |
| 1720 | |
| 1721 | nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list, |
| 1722 | &nr_scanned, sc, isolate_mode, lru); |
| 1723 | |
| 1724 | __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken); |
| 1725 | reclaim_stat->recent_scanned[file] += nr_taken; |
| 1726 | |
| 1727 | if (global_reclaim(sc)) { |
| 1728 | __mod_node_page_state(pgdat, NR_PAGES_SCANNED, nr_scanned); |
| 1729 | if (current_is_kswapd()) |
| 1730 | __count_vm_events(PGSCAN_KSWAPD, nr_scanned); |
| 1731 | else |
| 1732 | __count_vm_events(PGSCAN_DIRECT, nr_scanned); |
| 1733 | } |
| 1734 | spin_unlock_irq(&pgdat->lru_lock); |
| 1735 | |
| 1736 | if (nr_taken == 0) |
| 1737 | return 0; |
| 1738 | |
| 1739 | nr_reclaimed = shrink_page_list(&page_list, pgdat, sc, TTU_UNMAP, |
| 1740 | &nr_dirty, &nr_unqueued_dirty, &nr_congested, |
| 1741 | &nr_writeback, &nr_immediate, |
| 1742 | false); |
| 1743 | |
| 1744 | spin_lock_irq(&pgdat->lru_lock); |
| 1745 | |
| 1746 | if (global_reclaim(sc)) { |
| 1747 | if (current_is_kswapd()) |
| 1748 | __count_vm_events(PGSTEAL_KSWAPD, nr_reclaimed); |
| 1749 | else |
| 1750 | __count_vm_events(PGSTEAL_DIRECT, nr_reclaimed); |
| 1751 | } |
| 1752 | |
| 1753 | putback_inactive_pages(lruvec, &page_list); |
| 1754 | |
| 1755 | __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken); |
| 1756 | |
| 1757 | spin_unlock_irq(&pgdat->lru_lock); |
| 1758 | |
| 1759 | mem_cgroup_uncharge_list(&page_list); |
| 1760 | free_hot_cold_page_list(&page_list, true); |
| 1761 | |
| 1762 | /* |
| 1763 | * If reclaim is isolating dirty pages under writeback, it implies |
| 1764 | * that the long-lived page allocation rate is exceeding the page |
| 1765 | * laundering rate. Either the global limits are not being effective |
| 1766 | * at throttling processes due to the page distribution throughout |
| 1767 | * zones or there is heavy usage of a slow backing device. The |
| 1768 | * only option is to throttle from reclaim context which is not ideal |
| 1769 | * as there is no guarantee the dirtying process is throttled in the |
| 1770 | * same way balance_dirty_pages() manages. |
| 1771 | * |
| 1772 | * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number |
| 1773 | * of pages under pages flagged for immediate reclaim and stall if any |
| 1774 | * are encountered in the nr_immediate check below. |
| 1775 | */ |
| 1776 | if (nr_writeback && nr_writeback == nr_taken) |
| 1777 | set_bit(PGDAT_WRITEBACK, &pgdat->flags); |
| 1778 | |
| 1779 | /* |
| 1780 | * Legacy memcg will stall in page writeback so avoid forcibly |
| 1781 | * stalling here. |
| 1782 | */ |
| 1783 | if (sane_reclaim(sc)) { |
| 1784 | /* |
| 1785 | * Tag a zone as congested if all the dirty pages scanned were |
| 1786 | * backed by a congested BDI and wait_iff_congested will stall. |
| 1787 | */ |
| 1788 | if (nr_dirty && nr_dirty == nr_congested) |
| 1789 | set_bit(PGDAT_CONGESTED, &pgdat->flags); |
| 1790 | |
| 1791 | /* |
| 1792 | * If dirty pages are scanned that are not queued for IO, it |
| 1793 | * implies that flushers are not keeping up. In this case, flag |
| 1794 | * the pgdat PGDAT_DIRTY and kswapd will start writing pages from |
| 1795 | * reclaim context. |
| 1796 | */ |
| 1797 | if (nr_unqueued_dirty == nr_taken) |
| 1798 | set_bit(PGDAT_DIRTY, &pgdat->flags); |
| 1799 | |
| 1800 | /* |
| 1801 | * If kswapd scans pages marked marked for immediate |
| 1802 | * reclaim and under writeback (nr_immediate), it implies |
| 1803 | * that pages are cycling through the LRU faster than |
| 1804 | * they are written so also forcibly stall. |
| 1805 | */ |
| 1806 | if (nr_immediate && current_may_throttle()) |
| 1807 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
| 1808 | } |
| 1809 | |
| 1810 | /* |
| 1811 | * Stall direct reclaim for IO completions if underlying BDIs or zone |
| 1812 | * is congested. Allow kswapd to continue until it starts encountering |
| 1813 | * unqueued dirty pages or cycling through the LRU too quickly. |
| 1814 | */ |
| 1815 | if (!sc->hibernation_mode && !current_is_kswapd() && |
| 1816 | current_may_throttle()) |
| 1817 | wait_iff_congested(pgdat, BLK_RW_ASYNC, HZ/10); |
| 1818 | |
| 1819 | trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id, |
| 1820 | nr_scanned, nr_reclaimed, |
| 1821 | sc->priority, file); |
| 1822 | return nr_reclaimed; |
| 1823 | } |
| 1824 | |
| 1825 | /* |
| 1826 | * This moves pages from the active list to the inactive list. |
| 1827 | * |
| 1828 | * We move them the other way if the page is referenced by one or more |
| 1829 | * processes, from rmap. |
| 1830 | * |
| 1831 | * If the pages are mostly unmapped, the processing is fast and it is |
| 1832 | * appropriate to hold zone_lru_lock across the whole operation. But if |
| 1833 | * the pages are mapped, the processing is slow (page_referenced()) so we |
| 1834 | * should drop zone_lru_lock around each page. It's impossible to balance |
| 1835 | * this, so instead we remove the pages from the LRU while processing them. |
| 1836 | * It is safe to rely on PG_active against the non-LRU pages in here because |
| 1837 | * nobody will play with that bit on a non-LRU page. |
| 1838 | * |
| 1839 | * The downside is that we have to touch page->_refcount against each page. |
| 1840 | * But we had to alter page->flags anyway. |
| 1841 | */ |
| 1842 | |
| 1843 | static void move_active_pages_to_lru(struct lruvec *lruvec, |
| 1844 | struct list_head *list, |
| 1845 | struct list_head *pages_to_free, |
| 1846 | enum lru_list lru) |
| 1847 | { |
| 1848 | struct pglist_data *pgdat = lruvec_pgdat(lruvec); |
| 1849 | unsigned long pgmoved = 0; |
| 1850 | struct page *page; |
| 1851 | int nr_pages; |
| 1852 | |
| 1853 | while (!list_empty(list)) { |
| 1854 | page = lru_to_page(list); |
| 1855 | lruvec = mem_cgroup_page_lruvec(page, pgdat); |
| 1856 | |
| 1857 | VM_BUG_ON_PAGE(PageLRU(page), page); |
| 1858 | SetPageLRU(page); |
| 1859 | |
| 1860 | nr_pages = hpage_nr_pages(page); |
| 1861 | update_lru_size(lruvec, lru, page_zonenum(page), nr_pages); |
| 1862 | list_move(&page->lru, &lruvec->lists[lru]); |
| 1863 | pgmoved += nr_pages; |
| 1864 | |
| 1865 | if (put_page_testzero(page)) { |
| 1866 | __ClearPageLRU(page); |
| 1867 | __ClearPageActive(page); |
| 1868 | del_page_from_lru_list(page, lruvec, lru); |
| 1869 | |
| 1870 | if (unlikely(PageCompound(page))) { |
| 1871 | spin_unlock_irq(&pgdat->lru_lock); |
| 1872 | mem_cgroup_uncharge(page); |
| 1873 | (*get_compound_page_dtor(page))(page); |
| 1874 | spin_lock_irq(&pgdat->lru_lock); |
| 1875 | } else |
| 1876 | list_add(&page->lru, pages_to_free); |
| 1877 | } |
| 1878 | } |
| 1879 | |
| 1880 | if (!is_active_lru(lru)) |
| 1881 | __count_vm_events(PGDEACTIVATE, pgmoved); |
| 1882 | } |
| 1883 | |
| 1884 | static void shrink_active_list(unsigned long nr_to_scan, |
| 1885 | struct lruvec *lruvec, |
| 1886 | struct scan_control *sc, |
| 1887 | enum lru_list lru) |
| 1888 | { |
| 1889 | unsigned long nr_taken; |
| 1890 | unsigned long nr_scanned; |
| 1891 | unsigned long vm_flags; |
| 1892 | LIST_HEAD(l_hold); /* The pages which were snipped off */ |
| 1893 | LIST_HEAD(l_active); |
| 1894 | LIST_HEAD(l_inactive); |
| 1895 | struct page *page; |
| 1896 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
| 1897 | unsigned long nr_rotated = 0; |
| 1898 | isolate_mode_t isolate_mode = 0; |
| 1899 | int file = is_file_lru(lru); |
| 1900 | struct pglist_data *pgdat = lruvec_pgdat(lruvec); |
| 1901 | |
| 1902 | lru_add_drain(); |
| 1903 | |
| 1904 | if (!sc->may_unmap) |
| 1905 | isolate_mode |= ISOLATE_UNMAPPED; |
| 1906 | if (!sc->may_writepage) |
| 1907 | isolate_mode |= ISOLATE_CLEAN; |
| 1908 | |
| 1909 | spin_lock_irq(&pgdat->lru_lock); |
| 1910 | |
| 1911 | nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold, |
| 1912 | &nr_scanned, sc, isolate_mode, lru); |
| 1913 | |
| 1914 | __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken); |
| 1915 | reclaim_stat->recent_scanned[file] += nr_taken; |
| 1916 | |
| 1917 | if (global_reclaim(sc)) |
| 1918 | __mod_node_page_state(pgdat, NR_PAGES_SCANNED, nr_scanned); |
| 1919 | __count_vm_events(PGREFILL, nr_scanned); |
| 1920 | |
| 1921 | spin_unlock_irq(&pgdat->lru_lock); |
| 1922 | |
| 1923 | while (!list_empty(&l_hold)) { |
| 1924 | cond_resched(); |
| 1925 | page = lru_to_page(&l_hold); |
| 1926 | list_del(&page->lru); |
| 1927 | |
| 1928 | if (unlikely(!page_evictable(page))) { |
| 1929 | putback_lru_page(page); |
| 1930 | continue; |
| 1931 | } |
| 1932 | |
| 1933 | if (unlikely(buffer_heads_over_limit)) { |
| 1934 | if (page_has_private(page) && trylock_page(page)) { |
| 1935 | if (page_has_private(page)) |
| 1936 | try_to_release_page(page, 0); |
| 1937 | unlock_page(page); |
| 1938 | } |
| 1939 | } |
| 1940 | |
| 1941 | if (page_referenced(page, 0, sc->target_mem_cgroup, |
| 1942 | &vm_flags)) { |
| 1943 | nr_rotated += hpage_nr_pages(page); |
| 1944 | /* |
| 1945 | * Identify referenced, file-backed active pages and |
| 1946 | * give them one more trip around the active list. So |
| 1947 | * that executable code get better chances to stay in |
| 1948 | * memory under moderate memory pressure. Anon pages |
| 1949 | * are not likely to be evicted by use-once streaming |
| 1950 | * IO, plus JVM can create lots of anon VM_EXEC pages, |
| 1951 | * so we ignore them here. |
| 1952 | */ |
| 1953 | if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { |
| 1954 | list_add(&page->lru, &l_active); |
| 1955 | continue; |
| 1956 | } |
| 1957 | } |
| 1958 | |
| 1959 | ClearPageActive(page); /* we are de-activating */ |
| 1960 | list_add(&page->lru, &l_inactive); |
| 1961 | } |
| 1962 | |
| 1963 | /* |
| 1964 | * Move pages back to the lru list. |
| 1965 | */ |
| 1966 | spin_lock_irq(&pgdat->lru_lock); |
| 1967 | /* |
| 1968 | * Count referenced pages from currently used mappings as rotated, |
| 1969 | * even though only some of them are actually re-activated. This |
| 1970 | * helps balance scan pressure between file and anonymous pages in |
| 1971 | * get_scan_count. |
| 1972 | */ |
| 1973 | reclaim_stat->recent_rotated[file] += nr_rotated; |
| 1974 | |
| 1975 | move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru); |
| 1976 | move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE); |
| 1977 | __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken); |
| 1978 | spin_unlock_irq(&pgdat->lru_lock); |
| 1979 | |
| 1980 | mem_cgroup_uncharge_list(&l_hold); |
| 1981 | free_hot_cold_page_list(&l_hold, true); |
| 1982 | } |
| 1983 | |
| 1984 | /* |
| 1985 | * The inactive anon list should be small enough that the VM never has |
| 1986 | * to do too much work. |
| 1987 | * |
| 1988 | * The inactive file list should be small enough to leave most memory |
| 1989 | * to the established workingset on the scan-resistant active list, |
| 1990 | * but large enough to avoid thrashing the aggregate readahead window. |
| 1991 | * |
| 1992 | * Both inactive lists should also be large enough that each inactive |
| 1993 | * page has a chance to be referenced again before it is reclaimed. |
| 1994 | * |
| 1995 | * The inactive_ratio is the target ratio of ACTIVE to INACTIVE pages |
| 1996 | * on this LRU, maintained by the pageout code. A zone->inactive_ratio |
| 1997 | * of 3 means 3:1 or 25% of the pages are kept on the inactive list. |
| 1998 | * |
| 1999 | * total target max |
| 2000 | * memory ratio inactive |
| 2001 | * ------------------------------------- |
| 2002 | * 10MB 1 5MB |
| 2003 | * 100MB 1 50MB |
| 2004 | * 1GB 3 250MB |
| 2005 | * 10GB 10 0.9GB |
| 2006 | * 100GB 31 3GB |
| 2007 | * 1TB 101 10GB |
| 2008 | * 10TB 320 32GB |
| 2009 | */ |
| 2010 | static bool inactive_list_is_low(struct lruvec *lruvec, bool file, |
| 2011 | struct scan_control *sc) |
| 2012 | { |
| 2013 | unsigned long inactive_ratio; |
| 2014 | unsigned long inactive; |
| 2015 | unsigned long active; |
| 2016 | unsigned long gb; |
| 2017 | struct pglist_data *pgdat = lruvec_pgdat(lruvec); |
| 2018 | int zid; |
| 2019 | |
| 2020 | /* |
| 2021 | * If we don't have swap space, anonymous page deactivation |
| 2022 | * is pointless. |
| 2023 | */ |
| 2024 | if (!file && !total_swap_pages) |
| 2025 | return false; |
| 2026 | |
| 2027 | inactive = lruvec_lru_size(lruvec, file * LRU_FILE); |
| 2028 | active = lruvec_lru_size(lruvec, file * LRU_FILE + LRU_ACTIVE); |
| 2029 | |
| 2030 | /* |
| 2031 | * For zone-constrained allocations, it is necessary to check if |
| 2032 | * deactivations are required for lowmem to be reclaimed. This |
| 2033 | * calculates the inactive/active pages available in eligible zones. |
| 2034 | */ |
| 2035 | for (zid = sc->reclaim_idx + 1; zid < MAX_NR_ZONES; zid++) { |
| 2036 | struct zone *zone = &pgdat->node_zones[zid]; |
| 2037 | unsigned long inactive_zone, active_zone; |
| 2038 | |
| 2039 | if (!managed_zone(zone)) |
| 2040 | continue; |
| 2041 | |
| 2042 | inactive_zone = zone_page_state(zone, |
| 2043 | NR_ZONE_LRU_BASE + (file * LRU_FILE)); |
| 2044 | active_zone = zone_page_state(zone, |
| 2045 | NR_ZONE_LRU_BASE + (file * LRU_FILE) + LRU_ACTIVE); |
| 2046 | |
| 2047 | inactive -= min(inactive, inactive_zone); |
| 2048 | active -= min(active, active_zone); |
| 2049 | } |
| 2050 | |
| 2051 | gb = (inactive + active) >> (30 - PAGE_SHIFT); |
| 2052 | if (gb) |
| 2053 | inactive_ratio = int_sqrt(10 * gb); |
| 2054 | else |
| 2055 | inactive_ratio = 1; |
| 2056 | |
| 2057 | return inactive * inactive_ratio < active; |
| 2058 | } |
| 2059 | |
| 2060 | static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, |
| 2061 | struct lruvec *lruvec, struct scan_control *sc) |
| 2062 | { |
| 2063 | if (is_active_lru(lru)) { |
| 2064 | if (inactive_list_is_low(lruvec, is_file_lru(lru), sc)) |
| 2065 | shrink_active_list(nr_to_scan, lruvec, sc, lru); |
| 2066 | return 0; |
| 2067 | } |
| 2068 | |
| 2069 | return shrink_inactive_list(nr_to_scan, lruvec, sc, lru); |
| 2070 | } |
| 2071 | |
| 2072 | enum scan_balance { |
| 2073 | SCAN_EQUAL, |
| 2074 | SCAN_FRACT, |
| 2075 | SCAN_ANON, |
| 2076 | SCAN_FILE, |
| 2077 | }; |
| 2078 | |
| 2079 | /* |
| 2080 | * Determine how aggressively the anon and file LRU lists should be |
| 2081 | * scanned. The relative value of each set of LRU lists is determined |
| 2082 | * by looking at the fraction of the pages scanned we did rotate back |
| 2083 | * onto the active list instead of evict. |
| 2084 | * |
| 2085 | * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan |
| 2086 | * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan |
| 2087 | */ |
| 2088 | static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg, |
| 2089 | struct scan_control *sc, unsigned long *nr, |
| 2090 | unsigned long *lru_pages) |
| 2091 | { |
| 2092 | int swappiness = mem_cgroup_swappiness(memcg); |
| 2093 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
| 2094 | u64 fraction[2]; |
| 2095 | u64 denominator = 0; /* gcc */ |
| 2096 | struct pglist_data *pgdat = lruvec_pgdat(lruvec); |
| 2097 | unsigned long anon_prio, file_prio; |
| 2098 | enum scan_balance scan_balance; |
| 2099 | unsigned long anon, file; |
| 2100 | bool force_scan = false; |
| 2101 | unsigned long ap, fp; |
| 2102 | enum lru_list lru; |
| 2103 | bool some_scanned; |
| 2104 | int pass; |
| 2105 | |
| 2106 | /* |
| 2107 | * If the zone or memcg is small, nr[l] can be 0. This |
| 2108 | * results in no scanning on this priority and a potential |
| 2109 | * priority drop. Global direct reclaim can go to the next |
| 2110 | * zone and tends to have no problems. Global kswapd is for |
| 2111 | * zone balancing and it needs to scan a minimum amount. When |
| 2112 | * reclaiming for a memcg, a priority drop can cause high |
| 2113 | * latencies, so it's better to scan a minimum amount there as |
| 2114 | * well. |
| 2115 | */ |
| 2116 | if (current_is_kswapd()) { |
| 2117 | if (!pgdat_reclaimable(pgdat)) |
| 2118 | force_scan = true; |
| 2119 | if (!mem_cgroup_online(memcg)) |
| 2120 | force_scan = true; |
| 2121 | } |
| 2122 | if (!global_reclaim(sc)) |
| 2123 | force_scan = true; |
| 2124 | |
| 2125 | /* If we have no swap space, do not bother scanning anon pages. */ |
| 2126 | if (!sc->may_swap || mem_cgroup_get_nr_swap_pages(memcg) <= 0) { |
| 2127 | scan_balance = SCAN_FILE; |
| 2128 | goto out; |
| 2129 | } |
| 2130 | |
| 2131 | /* |
| 2132 | * Global reclaim will swap to prevent OOM even with no |
| 2133 | * swappiness, but memcg users want to use this knob to |
| 2134 | * disable swapping for individual groups completely when |
| 2135 | * using the memory controller's swap limit feature would be |
| 2136 | * too expensive. |
| 2137 | */ |
| 2138 | if (!global_reclaim(sc) && !swappiness) { |
| 2139 | scan_balance = SCAN_FILE; |
| 2140 | goto out; |
| 2141 | } |
| 2142 | |
| 2143 | /* |
| 2144 | * Do not apply any pressure balancing cleverness when the |
| 2145 | * system is close to OOM, scan both anon and file equally |
| 2146 | * (unless the swappiness setting disagrees with swapping). |
| 2147 | */ |
| 2148 | if (!sc->priority && swappiness) { |
| 2149 | scan_balance = SCAN_EQUAL; |
| 2150 | goto out; |
| 2151 | } |
| 2152 | |
| 2153 | /* |
| 2154 | * Prevent the reclaimer from falling into the cache trap: as |
| 2155 | * cache pages start out inactive, every cache fault will tip |
| 2156 | * the scan balance towards the file LRU. And as the file LRU |
| 2157 | * shrinks, so does the window for rotation from references. |
| 2158 | * This means we have a runaway feedback loop where a tiny |
| 2159 | * thrashing file LRU becomes infinitely more attractive than |
| 2160 | * anon pages. Try to detect this based on file LRU size. |
| 2161 | */ |
| 2162 | if (global_reclaim(sc)) { |
| 2163 | unsigned long pgdatfile; |
| 2164 | unsigned long pgdatfree; |
| 2165 | int z; |
| 2166 | unsigned long total_high_wmark = 0; |
| 2167 | |
| 2168 | pgdatfree = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES); |
| 2169 | pgdatfile = node_page_state(pgdat, NR_ACTIVE_FILE) + |
| 2170 | node_page_state(pgdat, NR_INACTIVE_FILE); |
| 2171 | |
| 2172 | for (z = 0; z < MAX_NR_ZONES; z++) { |
| 2173 | struct zone *zone = &pgdat->node_zones[z]; |
| 2174 | if (!managed_zone(zone)) |
| 2175 | continue; |
| 2176 | |
| 2177 | total_high_wmark += high_wmark_pages(zone); |
| 2178 | } |
| 2179 | |
| 2180 | if (unlikely(pgdatfile + pgdatfree <= total_high_wmark)) { |
| 2181 | scan_balance = SCAN_ANON; |
| 2182 | goto out; |
| 2183 | } |
| 2184 | } |
| 2185 | |
| 2186 | /* |
| 2187 | * If there is enough inactive page cache, i.e. if the size of the |
| 2188 | * inactive list is greater than that of the active list *and* the |
| 2189 | * inactive list actually has some pages to scan on this priority, we |
| 2190 | * do not reclaim anything from the anonymous working set right now. |
| 2191 | * Without the second condition we could end up never scanning an |
| 2192 | * lruvec even if it has plenty of old anonymous pages unless the |
| 2193 | * system is under heavy pressure. |
| 2194 | */ |
| 2195 | if (!inactive_list_is_low(lruvec, true, sc) && |
| 2196 | lruvec_lru_size(lruvec, LRU_INACTIVE_FILE) >> sc->priority) { |
| 2197 | scan_balance = SCAN_FILE; |
| 2198 | goto out; |
| 2199 | } |
| 2200 | |
| 2201 | scan_balance = SCAN_FRACT; |
| 2202 | |
| 2203 | /* |
| 2204 | * With swappiness at 100, anonymous and file have the same priority. |
| 2205 | * This scanning priority is essentially the inverse of IO cost. |
| 2206 | */ |
| 2207 | anon_prio = swappiness; |
| 2208 | file_prio = 200 - anon_prio; |
| 2209 | |
| 2210 | /* |
| 2211 | * OK, so we have swap space and a fair amount of page cache |
| 2212 | * pages. We use the recently rotated / recently scanned |
| 2213 | * ratios to determine how valuable each cache is. |
| 2214 | * |
| 2215 | * Because workloads change over time (and to avoid overflow) |
| 2216 | * we keep these statistics as a floating average, which ends |
| 2217 | * up weighing recent references more than old ones. |
| 2218 | * |
| 2219 | * anon in [0], file in [1] |
| 2220 | */ |
| 2221 | |
| 2222 | anon = lruvec_lru_size(lruvec, LRU_ACTIVE_ANON) + |
| 2223 | lruvec_lru_size(lruvec, LRU_INACTIVE_ANON); |
| 2224 | file = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE) + |
| 2225 | lruvec_lru_size(lruvec, LRU_INACTIVE_FILE); |
| 2226 | |
| 2227 | spin_lock_irq(&pgdat->lru_lock); |
| 2228 | if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { |
| 2229 | reclaim_stat->recent_scanned[0] /= 2; |
| 2230 | reclaim_stat->recent_rotated[0] /= 2; |
| 2231 | } |
| 2232 | |
| 2233 | if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { |
| 2234 | reclaim_stat->recent_scanned[1] /= 2; |
| 2235 | reclaim_stat->recent_rotated[1] /= 2; |
| 2236 | } |
| 2237 | |
| 2238 | /* |
| 2239 | * The amount of pressure on anon vs file pages is inversely |
| 2240 | * proportional to the fraction of recently scanned pages on |
| 2241 | * each list that were recently referenced and in active use. |
| 2242 | */ |
| 2243 | ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1); |
| 2244 | ap /= reclaim_stat->recent_rotated[0] + 1; |
| 2245 | |
| 2246 | fp = file_prio * (reclaim_stat->recent_scanned[1] + 1); |
| 2247 | fp /= reclaim_stat->recent_rotated[1] + 1; |
| 2248 | spin_unlock_irq(&pgdat->lru_lock); |
| 2249 | |
| 2250 | fraction[0] = ap; |
| 2251 | fraction[1] = fp; |
| 2252 | denominator = ap + fp + 1; |
| 2253 | out: |
| 2254 | some_scanned = false; |
| 2255 | /* Only use force_scan on second pass. */ |
| 2256 | for (pass = 0; !some_scanned && pass < 2; pass++) { |
| 2257 | *lru_pages = 0; |
| 2258 | for_each_evictable_lru(lru) { |
| 2259 | int file = is_file_lru(lru); |
| 2260 | unsigned long size; |
| 2261 | unsigned long scan; |
| 2262 | |
| 2263 | size = lruvec_lru_size(lruvec, lru); |
| 2264 | scan = size >> sc->priority; |
| 2265 | |
| 2266 | if (!scan && pass && force_scan) |
| 2267 | scan = min(size, SWAP_CLUSTER_MAX); |
| 2268 | |
| 2269 | switch (scan_balance) { |
| 2270 | case SCAN_EQUAL: |
| 2271 | /* Scan lists relative to size */ |
| 2272 | break; |
| 2273 | case SCAN_FRACT: |
| 2274 | /* |
| 2275 | * Scan types proportional to swappiness and |
| 2276 | * their relative recent reclaim efficiency. |
| 2277 | */ |
| 2278 | scan = div64_u64(scan * fraction[file], |
| 2279 | denominator); |
| 2280 | break; |
| 2281 | case SCAN_FILE: |
| 2282 | case SCAN_ANON: |
| 2283 | /* Scan one type exclusively */ |
| 2284 | if ((scan_balance == SCAN_FILE) != file) { |
| 2285 | size = 0; |
| 2286 | scan = 0; |
| 2287 | } |
| 2288 | break; |
| 2289 | default: |
| 2290 | /* Look ma, no brain */ |
| 2291 | BUG(); |
| 2292 | } |
| 2293 | |
| 2294 | *lru_pages += size; |
| 2295 | nr[lru] = scan; |
| 2296 | |
| 2297 | /* |
| 2298 | * Skip the second pass and don't force_scan, |
| 2299 | * if we found something to scan. |
| 2300 | */ |
| 2301 | some_scanned |= !!scan; |
| 2302 | } |
| 2303 | } |
| 2304 | } |
| 2305 | |
| 2306 | /* |
| 2307 | * This is a basic per-node page freer. Used by both kswapd and direct reclaim. |
| 2308 | */ |
| 2309 | static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memcg, |
| 2310 | struct scan_control *sc, unsigned long *lru_pages) |
| 2311 | { |
| 2312 | struct lruvec *lruvec = mem_cgroup_lruvec(pgdat, memcg); |
| 2313 | unsigned long nr[NR_LRU_LISTS]; |
| 2314 | unsigned long targets[NR_LRU_LISTS]; |
| 2315 | unsigned long nr_to_scan; |
| 2316 | enum lru_list lru; |
| 2317 | unsigned long nr_reclaimed = 0; |
| 2318 | unsigned long nr_to_reclaim = sc->nr_to_reclaim; |
| 2319 | struct blk_plug plug; |
| 2320 | bool scan_adjusted; |
| 2321 | |
| 2322 | get_scan_count(lruvec, memcg, sc, nr, lru_pages); |
| 2323 | |
| 2324 | /* Record the original scan target for proportional adjustments later */ |
| 2325 | memcpy(targets, nr, sizeof(nr)); |
| 2326 | |
| 2327 | /* |
| 2328 | * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal |
| 2329 | * event that can occur when there is little memory pressure e.g. |
| 2330 | * multiple streaming readers/writers. Hence, we do not abort scanning |
| 2331 | * when the requested number of pages are reclaimed when scanning at |
| 2332 | * DEF_PRIORITY on the assumption that the fact we are direct |
| 2333 | * reclaiming implies that kswapd is not keeping up and it is best to |
| 2334 | * do a batch of work at once. For memcg reclaim one check is made to |
| 2335 | * abort proportional reclaim if either the file or anon lru has already |
| 2336 | * dropped to zero at the first pass. |
| 2337 | */ |
| 2338 | scan_adjusted = (global_reclaim(sc) && !current_is_kswapd() && |
| 2339 | sc->priority == DEF_PRIORITY); |
| 2340 | |
| 2341 | blk_start_plug(&plug); |
| 2342 | while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || |
| 2343 | nr[LRU_INACTIVE_FILE]) { |
| 2344 | unsigned long nr_anon, nr_file, percentage; |
| 2345 | unsigned long nr_scanned; |
| 2346 | |
| 2347 | for_each_evictable_lru(lru) { |
| 2348 | if (nr[lru]) { |
| 2349 | nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX); |
| 2350 | nr[lru] -= nr_to_scan; |
| 2351 | |
| 2352 | nr_reclaimed += shrink_list(lru, nr_to_scan, |
| 2353 | lruvec, sc); |
| 2354 | } |
| 2355 | } |
| 2356 | |
| 2357 | if (nr_reclaimed < nr_to_reclaim || scan_adjusted) |
| 2358 | continue; |
| 2359 | |
| 2360 | /* |
| 2361 | * For kswapd and memcg, reclaim at least the number of pages |
| 2362 | * requested. Ensure that the anon and file LRUs are scanned |
| 2363 | * proportionally what was requested by get_scan_count(). We |
| 2364 | * stop reclaiming one LRU and reduce the amount scanning |
| 2365 | * proportional to the original scan target. |
| 2366 | */ |
| 2367 | nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE]; |
| 2368 | nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON]; |
| 2369 | |
| 2370 | /* |
| 2371 | * It's just vindictive to attack the larger once the smaller |
| 2372 | * has gone to zero. And given the way we stop scanning the |
| 2373 | * smaller below, this makes sure that we only make one nudge |
| 2374 | * towards proportionality once we've got nr_to_reclaim. |
| 2375 | */ |
| 2376 | if (!nr_file || !nr_anon) |
| 2377 | break; |
| 2378 | |
| 2379 | if (nr_file > nr_anon) { |
| 2380 | unsigned long scan_target = targets[LRU_INACTIVE_ANON] + |
| 2381 | targets[LRU_ACTIVE_ANON] + 1; |
| 2382 | lru = LRU_BASE; |
| 2383 | percentage = nr_anon * 100 / scan_target; |
| 2384 | } else { |
| 2385 | unsigned long scan_target = targets[LRU_INACTIVE_FILE] + |
| 2386 | targets[LRU_ACTIVE_FILE] + 1; |
| 2387 | lru = LRU_FILE; |
| 2388 | percentage = nr_file * 100 / scan_target; |
| 2389 | } |
| 2390 | |
| 2391 | /* Stop scanning the smaller of the LRU */ |
| 2392 | nr[lru] = 0; |
| 2393 | nr[lru + LRU_ACTIVE] = 0; |
| 2394 | |
| 2395 | /* |
| 2396 | * Recalculate the other LRU scan count based on its original |
| 2397 | * scan target and the percentage scanning already complete |
| 2398 | */ |
| 2399 | lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE; |
| 2400 | nr_scanned = targets[lru] - nr[lru]; |
| 2401 | nr[lru] = targets[lru] * (100 - percentage) / 100; |
| 2402 | nr[lru] -= min(nr[lru], nr_scanned); |
| 2403 | |
| 2404 | lru += LRU_ACTIVE; |
| 2405 | nr_scanned = targets[lru] - nr[lru]; |
| 2406 | nr[lru] = targets[lru] * (100 - percentage) / 100; |
| 2407 | nr[lru] -= min(nr[lru], nr_scanned); |
| 2408 | |
| 2409 | scan_adjusted = true; |
| 2410 | } |
| 2411 | blk_finish_plug(&plug); |
| 2412 | sc->nr_reclaimed += nr_reclaimed; |
| 2413 | |
| 2414 | /* |
| 2415 | * Even if we did not try to evict anon pages at all, we want to |
| 2416 | * rebalance the anon lru active/inactive ratio. |
| 2417 | */ |
| 2418 | if (inactive_list_is_low(lruvec, false, sc)) |
| 2419 | shrink_active_list(SWAP_CLUSTER_MAX, lruvec, |
| 2420 | sc, LRU_ACTIVE_ANON); |
| 2421 | } |
| 2422 | |
| 2423 | /* Use reclaim/compaction for costly allocs or under memory pressure */ |
| 2424 | static bool in_reclaim_compaction(struct scan_control *sc) |
| 2425 | { |
| 2426 | if (IS_ENABLED(CONFIG_COMPACTION) && sc->order && |
| 2427 | (sc->order > PAGE_ALLOC_COSTLY_ORDER || |
| 2428 | sc->priority < DEF_PRIORITY - 2)) |
| 2429 | return true; |
| 2430 | |
| 2431 | return false; |
| 2432 | } |
| 2433 | |
| 2434 | /* |
| 2435 | * Reclaim/compaction is used for high-order allocation requests. It reclaims |
| 2436 | * order-0 pages before compacting the zone. should_continue_reclaim() returns |
| 2437 | * true if more pages should be reclaimed such that when the page allocator |
| 2438 | * calls try_to_compact_zone() that it will have enough free pages to succeed. |
| 2439 | * It will give up earlier than that if there is difficulty reclaiming pages. |
| 2440 | */ |
| 2441 | static inline bool should_continue_reclaim(struct pglist_data *pgdat, |
| 2442 | unsigned long nr_reclaimed, |
| 2443 | unsigned long nr_scanned, |
| 2444 | struct scan_control *sc) |
| 2445 | { |
| 2446 | unsigned long pages_for_compaction; |
| 2447 | unsigned long inactive_lru_pages; |
| 2448 | int z; |
| 2449 | |
| 2450 | /* If not in reclaim/compaction mode, stop */ |
| 2451 | if (!in_reclaim_compaction(sc)) |
| 2452 | return false; |
| 2453 | |
| 2454 | /* Consider stopping depending on scan and reclaim activity */ |
| 2455 | if (sc->gfp_mask & __GFP_REPEAT) { |
| 2456 | /* |
| 2457 | * For __GFP_REPEAT allocations, stop reclaiming if the |
| 2458 | * full LRU list has been scanned and we are still failing |
| 2459 | * to reclaim pages. This full LRU scan is potentially |
| 2460 | * expensive but a __GFP_REPEAT caller really wants to succeed |
| 2461 | */ |
| 2462 | if (!nr_reclaimed && !nr_scanned) |
| 2463 | return false; |
| 2464 | } else { |
| 2465 | /* |
| 2466 | * For non-__GFP_REPEAT allocations which can presumably |
| 2467 | * fail without consequence, stop if we failed to reclaim |
| 2468 | * any pages from the last SWAP_CLUSTER_MAX number of |
| 2469 | * pages that were scanned. This will return to the |
| 2470 | * caller faster at the risk reclaim/compaction and |
| 2471 | * the resulting allocation attempt fails |
| 2472 | */ |
| 2473 | if (!nr_reclaimed) |
| 2474 | return false; |
| 2475 | } |
| 2476 | |
| 2477 | /* |
| 2478 | * If we have not reclaimed enough pages for compaction and the |
| 2479 | * inactive lists are large enough, continue reclaiming |
| 2480 | */ |
| 2481 | pages_for_compaction = compact_gap(sc->order); |
| 2482 | inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE); |
| 2483 | if (get_nr_swap_pages() > 0) |
| 2484 | inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON); |
| 2485 | if (sc->nr_reclaimed < pages_for_compaction && |
| 2486 | inactive_lru_pages > pages_for_compaction) |
| 2487 | return true; |
| 2488 | |
| 2489 | /* If compaction would go ahead or the allocation would succeed, stop */ |
| 2490 | for (z = 0; z <= sc->reclaim_idx; z++) { |
| 2491 | struct zone *zone = &pgdat->node_zones[z]; |
| 2492 | if (!managed_zone(zone)) |
| 2493 | continue; |
| 2494 | |
| 2495 | switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) { |
| 2496 | case COMPACT_SUCCESS: |
| 2497 | case COMPACT_CONTINUE: |
| 2498 | return false; |
| 2499 | default: |
| 2500 | /* check next zone */ |
| 2501 | ; |
| 2502 | } |
| 2503 | } |
| 2504 | return true; |
| 2505 | } |
| 2506 | |
| 2507 | static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc) |
| 2508 | { |
| 2509 | struct reclaim_state *reclaim_state = current->reclaim_state; |
| 2510 | unsigned long nr_reclaimed, nr_scanned; |
| 2511 | bool reclaimable = false; |
| 2512 | |
| 2513 | do { |
| 2514 | struct mem_cgroup *root = sc->target_mem_cgroup; |
| 2515 | struct mem_cgroup_reclaim_cookie reclaim = { |
| 2516 | .pgdat = pgdat, |
| 2517 | .priority = sc->priority, |
| 2518 | }; |
| 2519 | unsigned long node_lru_pages = 0; |
| 2520 | struct mem_cgroup *memcg; |
| 2521 | |
| 2522 | nr_reclaimed = sc->nr_reclaimed; |
| 2523 | nr_scanned = sc->nr_scanned; |
| 2524 | |
| 2525 | memcg = mem_cgroup_iter(root, NULL, &reclaim); |
| 2526 | do { |
| 2527 | unsigned long lru_pages; |
| 2528 | unsigned long reclaimed; |
| 2529 | unsigned long scanned; |
| 2530 | |
| 2531 | if (mem_cgroup_low(root, memcg)) { |
| 2532 | if (!sc->may_thrash) |
| 2533 | continue; |
| 2534 | mem_cgroup_events(memcg, MEMCG_LOW, 1); |
| 2535 | } |
| 2536 | |
| 2537 | reclaimed = sc->nr_reclaimed; |
| 2538 | scanned = sc->nr_scanned; |
| 2539 | |
| 2540 | shrink_node_memcg(pgdat, memcg, sc, &lru_pages); |
| 2541 | node_lru_pages += lru_pages; |
| 2542 | |
| 2543 | if (memcg) |
| 2544 | shrink_slab(sc->gfp_mask, pgdat->node_id, |
| 2545 | memcg, sc->nr_scanned - scanned, |
| 2546 | lru_pages); |
| 2547 | |
| 2548 | /* Record the group's reclaim efficiency */ |
| 2549 | vmpressure(sc->gfp_mask, memcg, false, |
| 2550 | sc->nr_scanned - scanned, |
| 2551 | sc->nr_reclaimed - reclaimed); |
| 2552 | |
| 2553 | /* |
| 2554 | * Direct reclaim and kswapd have to scan all memory |
| 2555 | * cgroups to fulfill the overall scan target for the |
| 2556 | * node. |
| 2557 | * |
| 2558 | * Limit reclaim, on the other hand, only cares about |
| 2559 | * nr_to_reclaim pages to be reclaimed and it will |
| 2560 | * retry with decreasing priority if one round over the |
| 2561 | * whole hierarchy is not sufficient. |
| 2562 | */ |
| 2563 | if (!global_reclaim(sc) && |
| 2564 | sc->nr_reclaimed >= sc->nr_to_reclaim) { |
| 2565 | mem_cgroup_iter_break(root, memcg); |
| 2566 | break; |
| 2567 | } |
| 2568 | } while ((memcg = mem_cgroup_iter(root, memcg, &reclaim))); |
| 2569 | |
| 2570 | /* |
| 2571 | * Shrink the slab caches in the same proportion that |
| 2572 | * the eligible LRU pages were scanned. |
| 2573 | */ |
| 2574 | if (global_reclaim(sc)) |
| 2575 | shrink_slab(sc->gfp_mask, pgdat->node_id, NULL, |
| 2576 | sc->nr_scanned - nr_scanned, |
| 2577 | node_lru_pages); |
| 2578 | |
| 2579 | if (reclaim_state) { |
| 2580 | sc->nr_reclaimed += reclaim_state->reclaimed_slab; |
| 2581 | reclaim_state->reclaimed_slab = 0; |
| 2582 | } |
| 2583 | |
| 2584 | /* Record the subtree's reclaim efficiency */ |
| 2585 | vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true, |
| 2586 | sc->nr_scanned - nr_scanned, |
| 2587 | sc->nr_reclaimed - nr_reclaimed); |
| 2588 | |
| 2589 | if (sc->nr_reclaimed - nr_reclaimed) |
| 2590 | reclaimable = true; |
| 2591 | |
| 2592 | } while (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed, |
| 2593 | sc->nr_scanned - nr_scanned, sc)); |
| 2594 | |
| 2595 | return reclaimable; |
| 2596 | } |
| 2597 | |
| 2598 | /* |
| 2599 | * Returns true if compaction should go ahead for a costly-order request, or |
| 2600 | * the allocation would already succeed without compaction. Return false if we |
| 2601 | * should reclaim first. |
| 2602 | */ |
| 2603 | static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) |
| 2604 | { |
| 2605 | unsigned long watermark; |
| 2606 | enum compact_result suitable; |
| 2607 | |
| 2608 | suitable = compaction_suitable(zone, sc->order, 0, sc->reclaim_idx); |
| 2609 | if (suitable == COMPACT_SUCCESS) |
| 2610 | /* Allocation should succeed already. Don't reclaim. */ |
| 2611 | return true; |
| 2612 | if (suitable == COMPACT_SKIPPED) |
| 2613 | /* Compaction cannot yet proceed. Do reclaim. */ |
| 2614 | return false; |
| 2615 | |
| 2616 | /* |
| 2617 | * Compaction is already possible, but it takes time to run and there |
| 2618 | * are potentially other callers using the pages just freed. So proceed |
| 2619 | * with reclaim to make a buffer of free pages available to give |
| 2620 | * compaction a reasonable chance of completing and allocating the page. |
| 2621 | * Note that we won't actually reclaim the whole buffer in one attempt |
| 2622 | * as the target watermark in should_continue_reclaim() is lower. But if |
| 2623 | * we are already above the high+gap watermark, don't reclaim at all. |
| 2624 | */ |
| 2625 | watermark = high_wmark_pages(zone) + compact_gap(sc->order); |
| 2626 | |
| 2627 | return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx); |
| 2628 | } |
| 2629 | |
| 2630 | /* |
| 2631 | * This is the direct reclaim path, for page-allocating processes. We only |
| 2632 | * try to reclaim pages from zones which will satisfy the caller's allocation |
| 2633 | * request. |
| 2634 | * |
| 2635 | * If a zone is deemed to be full of pinned pages then just give it a light |
| 2636 | * scan then give up on it. |
| 2637 | */ |
| 2638 | static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) |
| 2639 | { |
| 2640 | struct zoneref *z; |
| 2641 | struct zone *zone; |
| 2642 | unsigned long nr_soft_reclaimed; |
| 2643 | unsigned long nr_soft_scanned; |
| 2644 | gfp_t orig_mask; |
| 2645 | pg_data_t *last_pgdat = NULL; |
| 2646 | |
| 2647 | /* |
| 2648 | * If the number of buffer_heads in the machine exceeds the maximum |
| 2649 | * allowed level, force direct reclaim to scan the highmem zone as |
| 2650 | * highmem pages could be pinning lowmem pages storing buffer_heads |
| 2651 | */ |
| 2652 | orig_mask = sc->gfp_mask; |
| 2653 | if (buffer_heads_over_limit) { |
| 2654 | sc->gfp_mask |= __GFP_HIGHMEM; |
| 2655 | sc->reclaim_idx = gfp_zone(sc->gfp_mask); |
| 2656 | } |
| 2657 | |
| 2658 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
| 2659 | sc->reclaim_idx, sc->nodemask) { |
| 2660 | /* |
| 2661 | * Take care memory controller reclaiming has small influence |
| 2662 | * to global LRU. |
| 2663 | */ |
| 2664 | if (global_reclaim(sc)) { |
| 2665 | if (!cpuset_zone_allowed(zone, |
| 2666 | GFP_KERNEL | __GFP_HARDWALL)) |
| 2667 | continue; |
| 2668 | |
| 2669 | if (sc->priority != DEF_PRIORITY && |
| 2670 | !pgdat_reclaimable(zone->zone_pgdat)) |
| 2671 | continue; /* Let kswapd poll it */ |
| 2672 | |
| 2673 | /* |
| 2674 | * If we already have plenty of memory free for |
| 2675 | * compaction in this zone, don't free any more. |
| 2676 | * Even though compaction is invoked for any |
| 2677 | * non-zero order, only frequent costly order |
| 2678 | * reclamation is disruptive enough to become a |
| 2679 | * noticeable problem, like transparent huge |
| 2680 | * page allocations. |
| 2681 | */ |
| 2682 | if (IS_ENABLED(CONFIG_COMPACTION) && |
| 2683 | sc->order > PAGE_ALLOC_COSTLY_ORDER && |
| 2684 | compaction_ready(zone, sc)) { |
| 2685 | sc->compaction_ready = true; |
| 2686 | continue; |
| 2687 | } |
| 2688 | |
| 2689 | /* |
| 2690 | * Shrink each node in the zonelist once. If the |
| 2691 | * zonelist is ordered by zone (not the default) then a |
| 2692 | * node may be shrunk multiple times but in that case |
| 2693 | * the user prefers lower zones being preserved. |
| 2694 | */ |
| 2695 | if (zone->zone_pgdat == last_pgdat) |
| 2696 | continue; |
| 2697 | |
| 2698 | /* |
| 2699 | * This steals pages from memory cgroups over softlimit |
| 2700 | * and returns the number of reclaimed pages and |
| 2701 | * scanned pages. This works for global memory pressure |
| 2702 | * and balancing, not for a memcg's limit. |
| 2703 | */ |
| 2704 | nr_soft_scanned = 0; |
| 2705 | nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone->zone_pgdat, |
| 2706 | sc->order, sc->gfp_mask, |
| 2707 | &nr_soft_scanned); |
| 2708 | sc->nr_reclaimed += nr_soft_reclaimed; |
| 2709 | sc->nr_scanned += nr_soft_scanned; |
| 2710 | /* need some check for avoid more shrink_zone() */ |
| 2711 | } |
| 2712 | |
| 2713 | /* See comment about same check for global reclaim above */ |
| 2714 | if (zone->zone_pgdat == last_pgdat) |
| 2715 | continue; |
| 2716 | last_pgdat = zone->zone_pgdat; |
| 2717 | shrink_node(zone->zone_pgdat, sc); |
| 2718 | } |
| 2719 | |
| 2720 | /* |
| 2721 | * Restore to original mask to avoid the impact on the caller if we |
| 2722 | * promoted it to __GFP_HIGHMEM. |
| 2723 | */ |
| 2724 | sc->gfp_mask = orig_mask; |
| 2725 | } |
| 2726 | |
| 2727 | /* |
| 2728 | * This is the main entry point to direct page reclaim. |
| 2729 | * |
| 2730 | * If a full scan of the inactive list fails to free enough memory then we |
| 2731 | * are "out of memory" and something needs to be killed. |
| 2732 | * |
| 2733 | * If the caller is !__GFP_FS then the probability of a failure is reasonably |
| 2734 | * high - the zone may be full of dirty or under-writeback pages, which this |
| 2735 | * caller can't do much about. We kick the writeback threads and take explicit |
| 2736 | * naps in the hope that some of these pages can be written. But if the |
| 2737 | * allocating task holds filesystem locks which prevent writeout this might not |
| 2738 | * work, and the allocation attempt will fail. |
| 2739 | * |
| 2740 | * returns: 0, if no pages reclaimed |
| 2741 | * else, the number of pages reclaimed |
| 2742 | */ |
| 2743 | static unsigned long do_try_to_free_pages(struct zonelist *zonelist, |
| 2744 | struct scan_control *sc) |
| 2745 | { |
| 2746 | int initial_priority = sc->priority; |
| 2747 | unsigned long total_scanned = 0; |
| 2748 | unsigned long writeback_threshold; |
| 2749 | retry: |
| 2750 | delayacct_freepages_start(); |
| 2751 | |
| 2752 | if (global_reclaim(sc)) |
| 2753 | __count_zid_vm_events(ALLOCSTALL, sc->reclaim_idx, 1); |
| 2754 | |
| 2755 | do { |
| 2756 | vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup, |
| 2757 | sc->priority); |
| 2758 | sc->nr_scanned = 0; |
| 2759 | shrink_zones(zonelist, sc); |
| 2760 | |
| 2761 | total_scanned += sc->nr_scanned; |
| 2762 | if (sc->nr_reclaimed >= sc->nr_to_reclaim) |
| 2763 | break; |
| 2764 | |
| 2765 | if (sc->compaction_ready) |
| 2766 | break; |
| 2767 | |
| 2768 | /* |
| 2769 | * If we're getting trouble reclaiming, start doing |
| 2770 | * writepage even in laptop mode. |
| 2771 | */ |
| 2772 | if (sc->priority < DEF_PRIORITY - 2) |
| 2773 | sc->may_writepage = 1; |
| 2774 | |
| 2775 | /* |
| 2776 | * Try to write back as many pages as we just scanned. This |
| 2777 | * tends to cause slow streaming writers to write data to the |
| 2778 | * disk smoothly, at the dirtying rate, which is nice. But |
| 2779 | * that's undesirable in laptop mode, where we *want* lumpy |
| 2780 | * writeout. So in laptop mode, write out the whole world. |
| 2781 | */ |
| 2782 | writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; |
| 2783 | if (total_scanned > writeback_threshold) { |
| 2784 | wakeup_flusher_threads(laptop_mode ? 0 : total_scanned, |
| 2785 | WB_REASON_TRY_TO_FREE_PAGES); |
| 2786 | sc->may_writepage = 1; |
| 2787 | } |
| 2788 | } while (--sc->priority >= 0); |
| 2789 | |
| 2790 | delayacct_freepages_end(); |
| 2791 | |
| 2792 | if (sc->nr_reclaimed) |
| 2793 | return sc->nr_reclaimed; |
| 2794 | |
| 2795 | /* Aborted reclaim to try compaction? don't OOM, then */ |
| 2796 | if (sc->compaction_ready) |
| 2797 | return 1; |
| 2798 | |
| 2799 | /* Untapped cgroup reserves? Don't OOM, retry. */ |
| 2800 | if (!sc->may_thrash) { |
| 2801 | sc->priority = initial_priority; |
| 2802 | sc->may_thrash = 1; |
| 2803 | goto retry; |
| 2804 | } |
| 2805 | |
| 2806 | return 0; |
| 2807 | } |
| 2808 | |
| 2809 | static bool pfmemalloc_watermark_ok(pg_data_t *pgdat) |
| 2810 | { |
| 2811 | struct zone *zone; |
| 2812 | unsigned long pfmemalloc_reserve = 0; |
| 2813 | unsigned long free_pages = 0; |
| 2814 | int i; |
| 2815 | bool wmark_ok; |
| 2816 | |
| 2817 | for (i = 0; i <= ZONE_NORMAL; i++) { |
| 2818 | zone = &pgdat->node_zones[i]; |
| 2819 | if (!managed_zone(zone) || |
| 2820 | pgdat_reclaimable_pages(pgdat) == 0) |
| 2821 | continue; |
| 2822 | |
| 2823 | pfmemalloc_reserve += min_wmark_pages(zone); |
| 2824 | free_pages += zone_page_state(zone, NR_FREE_PAGES); |
| 2825 | } |
| 2826 | |
| 2827 | /* If there are no reserves (unexpected config) then do not throttle */ |
| 2828 | if (!pfmemalloc_reserve) |
| 2829 | return true; |
| 2830 | |
| 2831 | wmark_ok = free_pages > pfmemalloc_reserve / 2; |
| 2832 | |
| 2833 | /* kswapd must be awake if processes are being throttled */ |
| 2834 | if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) { |
| 2835 | pgdat->kswapd_classzone_idx = min(pgdat->kswapd_classzone_idx, |
| 2836 | (enum zone_type)ZONE_NORMAL); |
| 2837 | wake_up_interruptible(&pgdat->kswapd_wait); |
| 2838 | } |
| 2839 | |
| 2840 | return wmark_ok; |
| 2841 | } |
| 2842 | |
| 2843 | /* |
| 2844 | * Throttle direct reclaimers if backing storage is backed by the network |
| 2845 | * and the PFMEMALLOC reserve for the preferred node is getting dangerously |
| 2846 | * depleted. kswapd will continue to make progress and wake the processes |
| 2847 | * when the low watermark is reached. |
| 2848 | * |
| 2849 | * Returns true if a fatal signal was delivered during throttling. If this |
| 2850 | * happens, the page allocator should not consider triggering the OOM killer. |
| 2851 | */ |
| 2852 | static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist, |
| 2853 | nodemask_t *nodemask) |
| 2854 | { |
| 2855 | struct zoneref *z; |
| 2856 | struct zone *zone; |
| 2857 | pg_data_t *pgdat = NULL; |
| 2858 | |
| 2859 | /* |
| 2860 | * Kernel threads should not be throttled as they may be indirectly |
| 2861 | * responsible for cleaning pages necessary for reclaim to make forward |
| 2862 | * progress. kjournald for example may enter direct reclaim while |
| 2863 | * committing a transaction where throttling it could forcing other |
| 2864 | * processes to block on log_wait_commit(). |
| 2865 | */ |
| 2866 | if (current->flags & PF_KTHREAD) |
| 2867 | goto out; |
| 2868 | |
| 2869 | /* |
| 2870 | * If a fatal signal is pending, this process should not throttle. |
| 2871 | * It should return quickly so it can exit and free its memory |
| 2872 | */ |
| 2873 | if (fatal_signal_pending(current)) |
| 2874 | goto out; |
| 2875 | |
| 2876 | /* |
| 2877 | * Check if the pfmemalloc reserves are ok by finding the first node |
| 2878 | * with a usable ZONE_NORMAL or lower zone. The expectation is that |
| 2879 | * GFP_KERNEL will be required for allocating network buffers when |
| 2880 | * swapping over the network so ZONE_HIGHMEM is unusable. |
| 2881 | * |
| 2882 | * Throttling is based on the first usable node and throttled processes |
| 2883 | * wait on a queue until kswapd makes progress and wakes them. There |
| 2884 | * is an affinity then between processes waking up and where reclaim |
| 2885 | * progress has been made assuming the process wakes on the same node. |
| 2886 | * More importantly, processes running on remote nodes will not compete |
| 2887 | * for remote pfmemalloc reserves and processes on different nodes |
| 2888 | * should make reasonable progress. |
| 2889 | */ |
| 2890 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
| 2891 | gfp_zone(gfp_mask), nodemask) { |
| 2892 | if (zone_idx(zone) > ZONE_NORMAL) |
| 2893 | continue; |
| 2894 | |
| 2895 | /* Throttle based on the first usable node */ |
| 2896 | pgdat = zone->zone_pgdat; |
| 2897 | if (pfmemalloc_watermark_ok(pgdat)) |
| 2898 | goto out; |
| 2899 | break; |
| 2900 | } |
| 2901 | |
| 2902 | /* If no zone was usable by the allocation flags then do not throttle */ |
| 2903 | if (!pgdat) |
| 2904 | goto out; |
| 2905 | |
| 2906 | /* Account for the throttling */ |
| 2907 | count_vm_event(PGSCAN_DIRECT_THROTTLE); |
| 2908 | |
| 2909 | /* |
| 2910 | * If the caller cannot enter the filesystem, it's possible that it |
| 2911 | * is due to the caller holding an FS lock or performing a journal |
| 2912 | * transaction in the case of a filesystem like ext[3|4]. In this case, |
| 2913 | * it is not safe to block on pfmemalloc_wait as kswapd could be |
| 2914 | * blocked waiting on the same lock. Instead, throttle for up to a |
| 2915 | * second before continuing. |
| 2916 | */ |
| 2917 | if (!(gfp_mask & __GFP_FS)) { |
| 2918 | wait_event_interruptible_timeout(pgdat->pfmemalloc_wait, |
| 2919 | pfmemalloc_watermark_ok(pgdat), HZ); |
| 2920 | |
| 2921 | goto check_pending; |
| 2922 | } |
| 2923 | |
| 2924 | /* Throttle until kswapd wakes the process */ |
| 2925 | wait_event_killable(zone->zone_pgdat->pfmemalloc_wait, |
| 2926 | pfmemalloc_watermark_ok(pgdat)); |
| 2927 | |
| 2928 | check_pending: |
| 2929 | if (fatal_signal_pending(current)) |
| 2930 | return true; |
| 2931 | |
| 2932 | out: |
| 2933 | return false; |
| 2934 | } |
| 2935 | |
| 2936 | unsigned long try_to_free_pages(struct zonelist *zonelist, int order, |
| 2937 | gfp_t gfp_mask, nodemask_t *nodemask) |
| 2938 | { |
| 2939 | unsigned long nr_reclaimed; |
| 2940 | struct scan_control sc = { |
| 2941 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
| 2942 | .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)), |
| 2943 | .reclaim_idx = gfp_zone(gfp_mask), |
| 2944 | .order = order, |
| 2945 | .nodemask = nodemask, |
| 2946 | .priority = DEF_PRIORITY, |
| 2947 | .may_writepage = !laptop_mode, |
| 2948 | .may_unmap = 1, |
| 2949 | .may_swap = 1, |
| 2950 | }; |
| 2951 | |
| 2952 | /* |
| 2953 | * Do not enter reclaim if fatal signal was delivered while throttled. |
| 2954 | * 1 is returned so that the page allocator does not OOM kill at this |
| 2955 | * point. |
| 2956 | */ |
| 2957 | if (throttle_direct_reclaim(gfp_mask, zonelist, nodemask)) |
| 2958 | return 1; |
| 2959 | |
| 2960 | trace_mm_vmscan_direct_reclaim_begin(order, |
| 2961 | sc.may_writepage, |
| 2962 | gfp_mask, |
| 2963 | sc.reclaim_idx); |
| 2964 | |
| 2965 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc); |
| 2966 | |
| 2967 | trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); |
| 2968 | |
| 2969 | return nr_reclaimed; |
| 2970 | } |
| 2971 | |
| 2972 | #ifdef CONFIG_MEMCG |
| 2973 | |
| 2974 | unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg, |
| 2975 | gfp_t gfp_mask, bool noswap, |
| 2976 | pg_data_t *pgdat, |
| 2977 | unsigned long *nr_scanned) |
| 2978 | { |
| 2979 | struct scan_control sc = { |
| 2980 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
| 2981 | .target_mem_cgroup = memcg, |
| 2982 | .may_writepage = !laptop_mode, |
| 2983 | .may_unmap = 1, |
| 2984 | .reclaim_idx = MAX_NR_ZONES - 1, |
| 2985 | .may_swap = !noswap, |
| 2986 | }; |
| 2987 | unsigned long lru_pages; |
| 2988 | |
| 2989 | sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
| 2990 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); |
| 2991 | |
| 2992 | trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order, |
| 2993 | sc.may_writepage, |
| 2994 | sc.gfp_mask, |
| 2995 | sc.reclaim_idx); |
| 2996 | |
| 2997 | /* |
| 2998 | * NOTE: Although we can get the priority field, using it |
| 2999 | * here is not a good idea, since it limits the pages we can scan. |
| 3000 | * if we don't reclaim here, the shrink_node from balance_pgdat |
| 3001 | * will pick up pages from other mem cgroup's as well. We hack |
| 3002 | * the priority and make it zero. |
| 3003 | */ |
| 3004 | shrink_node_memcg(pgdat, memcg, &sc, &lru_pages); |
| 3005 | |
| 3006 | trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); |
| 3007 | |
| 3008 | *nr_scanned = sc.nr_scanned; |
| 3009 | return sc.nr_reclaimed; |
| 3010 | } |
| 3011 | |
| 3012 | unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, |
| 3013 | unsigned long nr_pages, |
| 3014 | gfp_t gfp_mask, |
| 3015 | bool may_swap) |
| 3016 | { |
| 3017 | struct zonelist *zonelist; |
| 3018 | unsigned long nr_reclaimed; |
| 3019 | int nid; |
| 3020 | struct scan_control sc = { |
| 3021 | .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), |
| 3022 | .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
| 3023 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), |
| 3024 | .reclaim_idx = MAX_NR_ZONES - 1, |
| 3025 | .target_mem_cgroup = memcg, |
| 3026 | .priority = DEF_PRIORITY, |
| 3027 | .may_writepage = !laptop_mode, |
| 3028 | .may_unmap = 1, |
| 3029 | .may_swap = may_swap, |
| 3030 | }; |
| 3031 | |
| 3032 | /* |
| 3033 | * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't |
| 3034 | * take care of from where we get pages. So the node where we start the |
| 3035 | * scan does not need to be the current node. |
| 3036 | */ |
| 3037 | nid = mem_cgroup_select_victim_node(memcg); |
| 3038 | |
| 3039 | zonelist = &NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK]; |
| 3040 | |
| 3041 | trace_mm_vmscan_memcg_reclaim_begin(0, |
| 3042 | sc.may_writepage, |
| 3043 | sc.gfp_mask, |
| 3044 | sc.reclaim_idx); |
| 3045 | |
| 3046 | current->flags |= PF_MEMALLOC; |
| 3047 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc); |
| 3048 | current->flags &= ~PF_MEMALLOC; |
| 3049 | |
| 3050 | trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); |
| 3051 | |
| 3052 | return nr_reclaimed; |
| 3053 | } |
| 3054 | #endif |
| 3055 | |
| 3056 | static void age_active_anon(struct pglist_data *pgdat, |
| 3057 | struct scan_control *sc) |
| 3058 | { |
| 3059 | struct mem_cgroup *memcg; |
| 3060 | |
| 3061 | if (!total_swap_pages) |
| 3062 | return; |
| 3063 | |
| 3064 | memcg = mem_cgroup_iter(NULL, NULL, NULL); |
| 3065 | do { |
| 3066 | struct lruvec *lruvec = mem_cgroup_lruvec(pgdat, memcg); |
| 3067 | |
| 3068 | if (inactive_list_is_low(lruvec, false, sc)) |
| 3069 | shrink_active_list(SWAP_CLUSTER_MAX, lruvec, |
| 3070 | sc, LRU_ACTIVE_ANON); |
| 3071 | |
| 3072 | memcg = mem_cgroup_iter(NULL, memcg, NULL); |
| 3073 | } while (memcg); |
| 3074 | } |
| 3075 | |
| 3076 | static bool zone_balanced(struct zone *zone, int order, int classzone_idx) |
| 3077 | { |
| 3078 | unsigned long mark = high_wmark_pages(zone); |
| 3079 | |
| 3080 | if (!zone_watermark_ok_safe(zone, order, mark, classzone_idx)) |
| 3081 | return false; |
| 3082 | |
| 3083 | /* |
| 3084 | * If any eligible zone is balanced then the node is not considered |
| 3085 | * to be congested or dirty |
| 3086 | */ |
| 3087 | clear_bit(PGDAT_CONGESTED, &zone->zone_pgdat->flags); |
| 3088 | clear_bit(PGDAT_DIRTY, &zone->zone_pgdat->flags); |
| 3089 | |
| 3090 | return true; |
| 3091 | } |
| 3092 | |
| 3093 | /* |
| 3094 | * Prepare kswapd for sleeping. This verifies that there are no processes |
| 3095 | * waiting in throttle_direct_reclaim() and that watermarks have been met. |
| 3096 | * |
| 3097 | * Returns true if kswapd is ready to sleep |
| 3098 | */ |
| 3099 | static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, int classzone_idx) |
| 3100 | { |
| 3101 | int i; |
| 3102 | |
| 3103 | /* |
| 3104 | * The throttled processes are normally woken up in balance_pgdat() as |
| 3105 | * soon as pfmemalloc_watermark_ok() is true. But there is a potential |
| 3106 | * race between when kswapd checks the watermarks and a process gets |
| 3107 | * throttled. There is also a potential race if processes get |
| 3108 | * throttled, kswapd wakes, a large process exits thereby balancing the |
| 3109 | * zones, which causes kswapd to exit balance_pgdat() before reaching |
| 3110 | * the wake up checks. If kswapd is going to sleep, no process should |
| 3111 | * be sleeping on pfmemalloc_wait, so wake them now if necessary. If |
| 3112 | * the wake up is premature, processes will wake kswapd and get |
| 3113 | * throttled again. The difference from wake ups in balance_pgdat() is |
| 3114 | * that here we are under prepare_to_wait(). |
| 3115 | */ |
| 3116 | if (waitqueue_active(&pgdat->pfmemalloc_wait)) |
| 3117 | wake_up_all(&pgdat->pfmemalloc_wait); |
| 3118 | |
| 3119 | for (i = 0; i <= classzone_idx; i++) { |
| 3120 | struct zone *zone = pgdat->node_zones + i; |
| 3121 | |
| 3122 | if (!managed_zone(zone)) |
| 3123 | continue; |
| 3124 | |
| 3125 | if (!zone_balanced(zone, order, classzone_idx)) |
| 3126 | return false; |
| 3127 | } |
| 3128 | |
| 3129 | return true; |
| 3130 | } |
| 3131 | |
| 3132 | /* |
| 3133 | * kswapd shrinks a node of pages that are at or below the highest usable |
| 3134 | * zone that is currently unbalanced. |
| 3135 | * |
| 3136 | * Returns true if kswapd scanned at least the requested number of pages to |
| 3137 | * reclaim or if the lack of progress was due to pages under writeback. |
| 3138 | * This is used to determine if the scanning priority needs to be raised. |
| 3139 | */ |
| 3140 | static bool kswapd_shrink_node(pg_data_t *pgdat, |
| 3141 | struct scan_control *sc) |
| 3142 | { |
| 3143 | struct zone *zone; |
| 3144 | int z; |
| 3145 | |
| 3146 | /* Reclaim a number of pages proportional to the number of zones */ |
| 3147 | sc->nr_to_reclaim = 0; |
| 3148 | for (z = 0; z <= sc->reclaim_idx; z++) { |
| 3149 | zone = pgdat->node_zones + z; |
| 3150 | if (!managed_zone(zone)) |
| 3151 | continue; |
| 3152 | |
| 3153 | sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX); |
| 3154 | } |
| 3155 | |
| 3156 | /* |
| 3157 | * Historically care was taken to put equal pressure on all zones but |
| 3158 | * now pressure is applied based on node LRU order. |
| 3159 | */ |
| 3160 | shrink_node(pgdat, sc); |
| 3161 | |
| 3162 | /* |
| 3163 | * Fragmentation may mean that the system cannot be rebalanced for |
| 3164 | * high-order allocations. If twice the allocation size has been |
| 3165 | * reclaimed then recheck watermarks only at order-0 to prevent |
| 3166 | * excessive reclaim. Assume that a process requested a high-order |
| 3167 | * can direct reclaim/compact. |
| 3168 | */ |
| 3169 | if (sc->order && sc->nr_reclaimed >= compact_gap(sc->order)) |
| 3170 | sc->order = 0; |
| 3171 | |
| 3172 | return sc->nr_scanned >= sc->nr_to_reclaim; |
| 3173 | } |
| 3174 | |
| 3175 | /* |
| 3176 | * For kswapd, balance_pgdat() will reclaim pages across a node from zones |
| 3177 | * that are eligible for use by the caller until at least one zone is |
| 3178 | * balanced. |
| 3179 | * |
| 3180 | * Returns the order kswapd finished reclaiming at. |
| 3181 | * |
| 3182 | * kswapd scans the zones in the highmem->normal->dma direction. It skips |
| 3183 | * zones which have free_pages > high_wmark_pages(zone), but once a zone is |
| 3184 | * found to have free_pages <= high_wmark_pages(zone), any page is that zone |
| 3185 | * or lower is eligible for reclaim until at least one usable zone is |
| 3186 | * balanced. |
| 3187 | */ |
| 3188 | static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) |
| 3189 | { |
| 3190 | int i; |
| 3191 | unsigned long nr_soft_reclaimed; |
| 3192 | unsigned long nr_soft_scanned; |
| 3193 | struct zone *zone; |
| 3194 | struct scan_control sc = { |
| 3195 | .gfp_mask = GFP_KERNEL, |
| 3196 | .order = order, |
| 3197 | .priority = DEF_PRIORITY, |
| 3198 | .may_writepage = !laptop_mode, |
| 3199 | .may_unmap = 1, |
| 3200 | .may_swap = 1, |
| 3201 | }; |
| 3202 | count_vm_event(PAGEOUTRUN); |
| 3203 | |
| 3204 | do { |
| 3205 | bool raise_priority = true; |
| 3206 | |
| 3207 | sc.nr_reclaimed = 0; |
| 3208 | sc.reclaim_idx = classzone_idx; |
| 3209 | |
| 3210 | /* |
| 3211 | * If the number of buffer_heads exceeds the maximum allowed |
| 3212 | * then consider reclaiming from all zones. This has a dual |
| 3213 | * purpose -- on 64-bit systems it is expected that |
| 3214 | * buffer_heads are stripped during active rotation. On 32-bit |
| 3215 | * systems, highmem pages can pin lowmem memory and shrinking |
| 3216 | * buffers can relieve lowmem pressure. Reclaim may still not |
| 3217 | * go ahead if all eligible zones for the original allocation |
| 3218 | * request are balanced to avoid excessive reclaim from kswapd. |
| 3219 | */ |
| 3220 | if (buffer_heads_over_limit) { |
| 3221 | for (i = MAX_NR_ZONES - 1; i >= 0; i--) { |
| 3222 | zone = pgdat->node_zones + i; |
| 3223 | if (!managed_zone(zone)) |
| 3224 | continue; |
| 3225 | |
| 3226 | sc.reclaim_idx = i; |
| 3227 | break; |
| 3228 | } |
| 3229 | } |
| 3230 | |
| 3231 | /* |
| 3232 | * Only reclaim if there are no eligible zones. Check from |
| 3233 | * high to low zone as allocations prefer higher zones. |
| 3234 | * Scanning from low to high zone would allow congestion to be |
| 3235 | * cleared during a very small window when a small low |
| 3236 | * zone was balanced even under extreme pressure when the |
| 3237 | * overall node may be congested. Note that sc.reclaim_idx |
| 3238 | * is not used as buffer_heads_over_limit may have adjusted |
| 3239 | * it. |
| 3240 | */ |
| 3241 | for (i = classzone_idx; i >= 0; i--) { |
| 3242 | zone = pgdat->node_zones + i; |
| 3243 | if (!managed_zone(zone)) |
| 3244 | continue; |
| 3245 | |
| 3246 | if (zone_balanced(zone, sc.order, classzone_idx)) |
| 3247 | goto out; |
| 3248 | } |
| 3249 | |
| 3250 | /* |
| 3251 | * Do some background aging of the anon list, to give |
| 3252 | * pages a chance to be referenced before reclaiming. All |
| 3253 | * pages are rotated regardless of classzone as this is |
| 3254 | * about consistent aging. |
| 3255 | */ |
| 3256 | age_active_anon(pgdat, &sc); |
| 3257 | |
| 3258 | /* |
| 3259 | * If we're getting trouble reclaiming, start doing writepage |
| 3260 | * even in laptop mode. |
| 3261 | */ |
| 3262 | if (sc.priority < DEF_PRIORITY - 2 || !pgdat_reclaimable(pgdat)) |
| 3263 | sc.may_writepage = 1; |
| 3264 | |
| 3265 | /* Call soft limit reclaim before calling shrink_node. */ |
| 3266 | sc.nr_scanned = 0; |
| 3267 | nr_soft_scanned = 0; |
| 3268 | nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(pgdat, sc.order, |
| 3269 | sc.gfp_mask, &nr_soft_scanned); |
| 3270 | sc.nr_reclaimed += nr_soft_reclaimed; |
| 3271 | |
| 3272 | /* |
| 3273 | * There should be no need to raise the scanning priority if |
| 3274 | * enough pages are already being scanned that that high |
| 3275 | * watermark would be met at 100% efficiency. |
| 3276 | */ |
| 3277 | if (kswapd_shrink_node(pgdat, &sc)) |
| 3278 | raise_priority = false; |
| 3279 | |
| 3280 | /* |
| 3281 | * If the low watermark is met there is no need for processes |
| 3282 | * to be throttled on pfmemalloc_wait as they should not be |
| 3283 | * able to safely make forward progress. Wake them |
| 3284 | */ |
| 3285 | if (waitqueue_active(&pgdat->pfmemalloc_wait) && |
| 3286 | pfmemalloc_watermark_ok(pgdat)) |
| 3287 | wake_up_all(&pgdat->pfmemalloc_wait); |
| 3288 | |
| 3289 | /* Check if kswapd should be suspending */ |
| 3290 | if (try_to_freeze() || kthread_should_stop()) |
| 3291 | break; |
| 3292 | |
| 3293 | /* |
| 3294 | * Raise priority if scanning rate is too low or there was no |
| 3295 | * progress in reclaiming pages |
| 3296 | */ |
| 3297 | if (raise_priority || !sc.nr_reclaimed) |
| 3298 | sc.priority--; |
| 3299 | } while (sc.priority >= 1); |
| 3300 | |
| 3301 | out: |
| 3302 | /* |
| 3303 | * Return the order kswapd stopped reclaiming at as |
| 3304 | * prepare_kswapd_sleep() takes it into account. If another caller |
| 3305 | * entered the allocator slow path while kswapd was awake, order will |
| 3306 | * remain at the higher level. |
| 3307 | */ |
| 3308 | return sc.order; |
| 3309 | } |
| 3310 | |
| 3311 | static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order, |
| 3312 | unsigned int classzone_idx) |
| 3313 | { |
| 3314 | long remaining = 0; |
| 3315 | DEFINE_WAIT(wait); |
| 3316 | |
| 3317 | if (freezing(current) || kthread_should_stop()) |
| 3318 | return; |
| 3319 | |
| 3320 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
| 3321 | |
| 3322 | /* Try to sleep for a short interval */ |
| 3323 | if (prepare_kswapd_sleep(pgdat, reclaim_order, classzone_idx)) { |
| 3324 | /* |
| 3325 | * Compaction records what page blocks it recently failed to |
| 3326 | * isolate pages from and skips them in the future scanning. |
| 3327 | * When kswapd is going to sleep, it is reasonable to assume |
| 3328 | * that pages and compaction may succeed so reset the cache. |
| 3329 | */ |
| 3330 | reset_isolation_suitable(pgdat); |
| 3331 | |
| 3332 | /* |
| 3333 | * We have freed the memory, now we should compact it to make |
| 3334 | * allocation of the requested order possible. |
| 3335 | */ |
| 3336 | wakeup_kcompactd(pgdat, alloc_order, classzone_idx); |
| 3337 | |
| 3338 | remaining = schedule_timeout(HZ/10); |
| 3339 | |
| 3340 | /* |
| 3341 | * If woken prematurely then reset kswapd_classzone_idx and |
| 3342 | * order. The values will either be from a wakeup request or |
| 3343 | * the previous request that slept prematurely. |
| 3344 | */ |
| 3345 | if (remaining) { |
| 3346 | pgdat->kswapd_classzone_idx = max(pgdat->kswapd_classzone_idx, classzone_idx); |
| 3347 | pgdat->kswapd_order = max(pgdat->kswapd_order, reclaim_order); |
| 3348 | } |
| 3349 | |
| 3350 | finish_wait(&pgdat->kswapd_wait, &wait); |
| 3351 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
| 3352 | } |
| 3353 | |
| 3354 | /* |
| 3355 | * After a short sleep, check if it was a premature sleep. If not, then |
| 3356 | * go fully to sleep until explicitly woken up. |
| 3357 | */ |
| 3358 | if (!remaining && |
| 3359 | prepare_kswapd_sleep(pgdat, reclaim_order, classzone_idx)) { |
| 3360 | trace_mm_vmscan_kswapd_sleep(pgdat->node_id); |
| 3361 | |
| 3362 | /* |
| 3363 | * vmstat counters are not perfectly accurate and the estimated |
| 3364 | * value for counters such as NR_FREE_PAGES can deviate from the |
| 3365 | * true value by nr_online_cpus * threshold. To avoid the zone |
| 3366 | * watermarks being breached while under pressure, we reduce the |
| 3367 | * per-cpu vmstat threshold while kswapd is awake and restore |
| 3368 | * them before going back to sleep. |
| 3369 | */ |
| 3370 | set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); |
| 3371 | |
| 3372 | if (!kthread_should_stop()) |
| 3373 | schedule(); |
| 3374 | |
| 3375 | set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); |
| 3376 | } else { |
| 3377 | if (remaining) |
| 3378 | count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); |
| 3379 | else |
| 3380 | count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); |
| 3381 | } |
| 3382 | finish_wait(&pgdat->kswapd_wait, &wait); |
| 3383 | } |
| 3384 | |
| 3385 | /* |
| 3386 | * The background pageout daemon, started as a kernel thread |
| 3387 | * from the init process. |
| 3388 | * |
| 3389 | * This basically trickles out pages so that we have _some_ |
| 3390 | * free memory available even if there is no other activity |
| 3391 | * that frees anything up. This is needed for things like routing |
| 3392 | * etc, where we otherwise might have all activity going on in |
| 3393 | * asynchronous contexts that cannot page things out. |
| 3394 | * |
| 3395 | * If there are applications that are active memory-allocators |
| 3396 | * (most normal use), this basically shouldn't matter. |
| 3397 | */ |
| 3398 | static int kswapd(void *p) |
| 3399 | { |
| 3400 | unsigned int alloc_order, reclaim_order, classzone_idx; |
| 3401 | pg_data_t *pgdat = (pg_data_t*)p; |
| 3402 | struct task_struct *tsk = current; |
| 3403 | |
| 3404 | struct reclaim_state reclaim_state = { |
| 3405 | .reclaimed_slab = 0, |
| 3406 | }; |
| 3407 | const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); |
| 3408 | |
| 3409 | lockdep_set_current_reclaim_state(GFP_KERNEL); |
| 3410 | |
| 3411 | if (!cpumask_empty(cpumask)) |
| 3412 | set_cpus_allowed_ptr(tsk, cpumask); |
| 3413 | current->reclaim_state = &reclaim_state; |
| 3414 | |
| 3415 | /* |
| 3416 | * Tell the memory management that we're a "memory allocator", |
| 3417 | * and that if we need more memory we should get access to it |
| 3418 | * regardless (see "__alloc_pages()"). "kswapd" should |
| 3419 | * never get caught in the normal page freeing logic. |
| 3420 | * |
| 3421 | * (Kswapd normally doesn't need memory anyway, but sometimes |
| 3422 | * you need a small amount of memory in order to be able to |
| 3423 | * page out something else, and this flag essentially protects |
| 3424 | * us from recursively trying to free more memory as we're |
| 3425 | * trying to free the first piece of memory in the first place). |
| 3426 | */ |
| 3427 | tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; |
| 3428 | set_freezable(); |
| 3429 | |
| 3430 | pgdat->kswapd_order = alloc_order = reclaim_order = 0; |
| 3431 | pgdat->kswapd_classzone_idx = classzone_idx = 0; |
| 3432 | for ( ; ; ) { |
| 3433 | bool ret; |
| 3434 | |
| 3435 | kswapd_try_sleep: |
| 3436 | kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order, |
| 3437 | classzone_idx); |
| 3438 | |
| 3439 | /* Read the new order and classzone_idx */ |
| 3440 | alloc_order = reclaim_order = pgdat->kswapd_order; |
| 3441 | classzone_idx = pgdat->kswapd_classzone_idx; |
| 3442 | pgdat->kswapd_order = 0; |
| 3443 | pgdat->kswapd_classzone_idx = 0; |
| 3444 | |
| 3445 | ret = try_to_freeze(); |
| 3446 | if (kthread_should_stop()) |
| 3447 | break; |
| 3448 | |
| 3449 | /* |
| 3450 | * We can speed up thawing tasks if we don't call balance_pgdat |
| 3451 | * after returning from the refrigerator |
| 3452 | */ |
| 3453 | if (ret) |
| 3454 | continue; |
| 3455 | |
| 3456 | /* |
| 3457 | * Reclaim begins at the requested order but if a high-order |
| 3458 | * reclaim fails then kswapd falls back to reclaiming for |
| 3459 | * order-0. If that happens, kswapd will consider sleeping |
| 3460 | * for the order it finished reclaiming at (reclaim_order) |
| 3461 | * but kcompactd is woken to compact for the original |
| 3462 | * request (alloc_order). |
| 3463 | */ |
| 3464 | trace_mm_vmscan_kswapd_wake(pgdat->node_id, classzone_idx, |
| 3465 | alloc_order); |
| 3466 | reclaim_order = balance_pgdat(pgdat, alloc_order, classzone_idx); |
| 3467 | if (reclaim_order < alloc_order) |
| 3468 | goto kswapd_try_sleep; |
| 3469 | |
| 3470 | alloc_order = reclaim_order = pgdat->kswapd_order; |
| 3471 | classzone_idx = pgdat->kswapd_classzone_idx; |
| 3472 | } |
| 3473 | |
| 3474 | tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD); |
| 3475 | current->reclaim_state = NULL; |
| 3476 | lockdep_clear_current_reclaim_state(); |
| 3477 | |
| 3478 | return 0; |
| 3479 | } |
| 3480 | |
| 3481 | /* |
| 3482 | * A zone is low on free memory, so wake its kswapd task to service it. |
| 3483 | */ |
| 3484 | void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) |
| 3485 | { |
| 3486 | pg_data_t *pgdat; |
| 3487 | int z; |
| 3488 | |
| 3489 | if (!managed_zone(zone)) |
| 3490 | return; |
| 3491 | |
| 3492 | if (!cpuset_zone_allowed(zone, GFP_KERNEL | __GFP_HARDWALL)) |
| 3493 | return; |
| 3494 | pgdat = zone->zone_pgdat; |
| 3495 | pgdat->kswapd_classzone_idx = max(pgdat->kswapd_classzone_idx, classzone_idx); |
| 3496 | pgdat->kswapd_order = max(pgdat->kswapd_order, order); |
| 3497 | if (!waitqueue_active(&pgdat->kswapd_wait)) |
| 3498 | return; |
| 3499 | |
| 3500 | /* Only wake kswapd if all zones are unbalanced */ |
| 3501 | for (z = 0; z <= classzone_idx; z++) { |
| 3502 | zone = pgdat->node_zones + z; |
| 3503 | if (!managed_zone(zone)) |
| 3504 | continue; |
| 3505 | |
| 3506 | if (zone_balanced(zone, order, classzone_idx)) |
| 3507 | return; |
| 3508 | } |
| 3509 | |
| 3510 | trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); |
| 3511 | wake_up_interruptible(&pgdat->kswapd_wait); |
| 3512 | } |
| 3513 | |
| 3514 | #ifdef CONFIG_HIBERNATION |
| 3515 | /* |
| 3516 | * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of |
| 3517 | * freed pages. |
| 3518 | * |
| 3519 | * Rather than trying to age LRUs the aim is to preserve the overall |
| 3520 | * LRU order by reclaiming preferentially |
| 3521 | * inactive > active > active referenced > active mapped |
| 3522 | */ |
| 3523 | unsigned long shrink_all_memory(unsigned long nr_to_reclaim) |
| 3524 | { |
| 3525 | struct reclaim_state reclaim_state; |
| 3526 | struct scan_control sc = { |
| 3527 | .nr_to_reclaim = nr_to_reclaim, |
| 3528 | .gfp_mask = GFP_HIGHUSER_MOVABLE, |
| 3529 | .reclaim_idx = MAX_NR_ZONES - 1, |
| 3530 | .priority = DEF_PRIORITY, |
| 3531 | .may_writepage = 1, |
| 3532 | .may_unmap = 1, |
| 3533 | .may_swap = 1, |
| 3534 | .hibernation_mode = 1, |
| 3535 | }; |
| 3536 | struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); |
| 3537 | struct task_struct *p = current; |
| 3538 | unsigned long nr_reclaimed; |
| 3539 | |
| 3540 | p->flags |= PF_MEMALLOC; |
| 3541 | lockdep_set_current_reclaim_state(sc.gfp_mask); |
| 3542 | reclaim_state.reclaimed_slab = 0; |
| 3543 | p->reclaim_state = &reclaim_state; |
| 3544 | |
| 3545 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc); |
| 3546 | |
| 3547 | p->reclaim_state = NULL; |
| 3548 | lockdep_clear_current_reclaim_state(); |
| 3549 | p->flags &= ~PF_MEMALLOC; |
| 3550 | |
| 3551 | return nr_reclaimed; |
| 3552 | } |
| 3553 | #endif /* CONFIG_HIBERNATION */ |
| 3554 | |
| 3555 | /* It's optimal to keep kswapds on the same CPUs as their memory, but |
| 3556 | not required for correctness. So if the last cpu in a node goes |
| 3557 | away, we get changed to run anywhere: as the first one comes back, |
| 3558 | restore their cpu bindings. */ |
| 3559 | static int cpu_callback(struct notifier_block *nfb, unsigned long action, |
| 3560 | void *hcpu) |
| 3561 | { |
| 3562 | int nid; |
| 3563 | |
| 3564 | if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { |
| 3565 | for_each_node_state(nid, N_MEMORY) { |
| 3566 | pg_data_t *pgdat = NODE_DATA(nid); |
| 3567 | const struct cpumask *mask; |
| 3568 | |
| 3569 | mask = cpumask_of_node(pgdat->node_id); |
| 3570 | |
| 3571 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) |
| 3572 | /* One of our CPUs online: restore mask */ |
| 3573 | set_cpus_allowed_ptr(pgdat->kswapd, mask); |
| 3574 | } |
| 3575 | } |
| 3576 | return NOTIFY_OK; |
| 3577 | } |
| 3578 | |
| 3579 | /* |
| 3580 | * This kswapd start function will be called by init and node-hot-add. |
| 3581 | * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. |
| 3582 | */ |
| 3583 | int kswapd_run(int nid) |
| 3584 | { |
| 3585 | pg_data_t *pgdat = NODE_DATA(nid); |
| 3586 | int ret = 0; |
| 3587 | |
| 3588 | if (pgdat->kswapd) |
| 3589 | return 0; |
| 3590 | |
| 3591 | pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); |
| 3592 | if (IS_ERR(pgdat->kswapd)) { |
| 3593 | /* failure at boot is fatal */ |
| 3594 | BUG_ON(system_state == SYSTEM_BOOTING); |
| 3595 | pr_err("Failed to start kswapd on node %d\n", nid); |
| 3596 | ret = PTR_ERR(pgdat->kswapd); |
| 3597 | pgdat->kswapd = NULL; |
| 3598 | } |
| 3599 | return ret; |
| 3600 | } |
| 3601 | |
| 3602 | /* |
| 3603 | * Called by memory hotplug when all memory in a node is offlined. Caller must |
| 3604 | * hold mem_hotplug_begin/end(). |
| 3605 | */ |
| 3606 | void kswapd_stop(int nid) |
| 3607 | { |
| 3608 | struct task_struct *kswapd = NODE_DATA(nid)->kswapd; |
| 3609 | |
| 3610 | if (kswapd) { |
| 3611 | kthread_stop(kswapd); |
| 3612 | NODE_DATA(nid)->kswapd = NULL; |
| 3613 | } |
| 3614 | } |
| 3615 | |
| 3616 | static int __init kswapd_init(void) |
| 3617 | { |
| 3618 | int nid; |
| 3619 | |
| 3620 | swap_setup(); |
| 3621 | for_each_node_state(nid, N_MEMORY) |
| 3622 | kswapd_run(nid); |
| 3623 | hotcpu_notifier(cpu_callback, 0); |
| 3624 | return 0; |
| 3625 | } |
| 3626 | |
| 3627 | module_init(kswapd_init) |
| 3628 | |
| 3629 | #ifdef CONFIG_NUMA |
| 3630 | /* |
| 3631 | * Node reclaim mode |
| 3632 | * |
| 3633 | * If non-zero call node_reclaim when the number of free pages falls below |
| 3634 | * the watermarks. |
| 3635 | */ |
| 3636 | int node_reclaim_mode __read_mostly; |
| 3637 | |
| 3638 | #define RECLAIM_OFF 0 |
| 3639 | #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ |
| 3640 | #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ |
| 3641 | #define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */ |
| 3642 | |
| 3643 | /* |
| 3644 | * Priority for NODE_RECLAIM. This determines the fraction of pages |
| 3645 | * of a node considered for each zone_reclaim. 4 scans 1/16th of |
| 3646 | * a zone. |
| 3647 | */ |
| 3648 | #define NODE_RECLAIM_PRIORITY 4 |
| 3649 | |
| 3650 | /* |
| 3651 | * Percentage of pages in a zone that must be unmapped for node_reclaim to |
| 3652 | * occur. |
| 3653 | */ |
| 3654 | int sysctl_min_unmapped_ratio = 1; |
| 3655 | |
| 3656 | /* |
| 3657 | * If the number of slab pages in a zone grows beyond this percentage then |
| 3658 | * slab reclaim needs to occur. |
| 3659 | */ |
| 3660 | int sysctl_min_slab_ratio = 5; |
| 3661 | |
| 3662 | static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat) |
| 3663 | { |
| 3664 | unsigned long file_mapped = node_page_state(pgdat, NR_FILE_MAPPED); |
| 3665 | unsigned long file_lru = node_page_state(pgdat, NR_INACTIVE_FILE) + |
| 3666 | node_page_state(pgdat, NR_ACTIVE_FILE); |
| 3667 | |
| 3668 | /* |
| 3669 | * It's possible for there to be more file mapped pages than |
| 3670 | * accounted for by the pages on the file LRU lists because |
| 3671 | * tmpfs pages accounted for as ANON can also be FILE_MAPPED |
| 3672 | */ |
| 3673 | return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; |
| 3674 | } |
| 3675 | |
| 3676 | /* Work out how many page cache pages we can reclaim in this reclaim_mode */ |
| 3677 | static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat) |
| 3678 | { |
| 3679 | unsigned long nr_pagecache_reclaimable; |
| 3680 | unsigned long delta = 0; |
| 3681 | |
| 3682 | /* |
| 3683 | * If RECLAIM_UNMAP is set, then all file pages are considered |
| 3684 | * potentially reclaimable. Otherwise, we have to worry about |
| 3685 | * pages like swapcache and node_unmapped_file_pages() provides |
| 3686 | * a better estimate |
| 3687 | */ |
| 3688 | if (node_reclaim_mode & RECLAIM_UNMAP) |
| 3689 | nr_pagecache_reclaimable = node_page_state(pgdat, NR_FILE_PAGES); |
| 3690 | else |
| 3691 | nr_pagecache_reclaimable = node_unmapped_file_pages(pgdat); |
| 3692 | |
| 3693 | /* If we can't clean pages, remove dirty pages from consideration */ |
| 3694 | if (!(node_reclaim_mode & RECLAIM_WRITE)) |
| 3695 | delta += node_page_state(pgdat, NR_FILE_DIRTY); |
| 3696 | |
| 3697 | /* Watch for any possible underflows due to delta */ |
| 3698 | if (unlikely(delta > nr_pagecache_reclaimable)) |
| 3699 | delta = nr_pagecache_reclaimable; |
| 3700 | |
| 3701 | return nr_pagecache_reclaimable - delta; |
| 3702 | } |
| 3703 | |
| 3704 | /* |
| 3705 | * Try to free up some pages from this node through reclaim. |
| 3706 | */ |
| 3707 | static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) |
| 3708 | { |
| 3709 | /* Minimum pages needed in order to stay on node */ |
| 3710 | const unsigned long nr_pages = 1 << order; |
| 3711 | struct task_struct *p = current; |
| 3712 | struct reclaim_state reclaim_state; |
| 3713 | int classzone_idx = gfp_zone(gfp_mask); |
| 3714 | struct scan_control sc = { |
| 3715 | .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), |
| 3716 | .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)), |
| 3717 | .order = order, |
| 3718 | .priority = NODE_RECLAIM_PRIORITY, |
| 3719 | .may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE), |
| 3720 | .may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP), |
| 3721 | .may_swap = 1, |
| 3722 | .reclaim_idx = classzone_idx, |
| 3723 | }; |
| 3724 | |
| 3725 | cond_resched(); |
| 3726 | /* |
| 3727 | * We need to be able to allocate from the reserves for RECLAIM_UNMAP |
| 3728 | * and we also need to be able to write out pages for RECLAIM_WRITE |
| 3729 | * and RECLAIM_UNMAP. |
| 3730 | */ |
| 3731 | p->flags |= PF_MEMALLOC | PF_SWAPWRITE; |
| 3732 | lockdep_set_current_reclaim_state(gfp_mask); |
| 3733 | reclaim_state.reclaimed_slab = 0; |
| 3734 | p->reclaim_state = &reclaim_state; |
| 3735 | |
| 3736 | if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages) { |
| 3737 | /* |
| 3738 | * Free memory by calling shrink zone with increasing |
| 3739 | * priorities until we have enough memory freed. |
| 3740 | */ |
| 3741 | do { |
| 3742 | shrink_node(pgdat, &sc); |
| 3743 | } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0); |
| 3744 | } |
| 3745 | |
| 3746 | p->reclaim_state = NULL; |
| 3747 | current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); |
| 3748 | lockdep_clear_current_reclaim_state(); |
| 3749 | return sc.nr_reclaimed >= nr_pages; |
| 3750 | } |
| 3751 | |
| 3752 | int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) |
| 3753 | { |
| 3754 | int ret; |
| 3755 | |
| 3756 | /* |
| 3757 | * Node reclaim reclaims unmapped file backed pages and |
| 3758 | * slab pages if we are over the defined limits. |
| 3759 | * |
| 3760 | * A small portion of unmapped file backed pages is needed for |
| 3761 | * file I/O otherwise pages read by file I/O will be immediately |
| 3762 | * thrown out if the node is overallocated. So we do not reclaim |
| 3763 | * if less than a specified percentage of the node is used by |
| 3764 | * unmapped file backed pages. |
| 3765 | */ |
| 3766 | if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages && |
| 3767 | sum_zone_node_page_state(pgdat->node_id, NR_SLAB_RECLAIMABLE) <= pgdat->min_slab_pages) |
| 3768 | return NODE_RECLAIM_FULL; |
| 3769 | |
| 3770 | if (!pgdat_reclaimable(pgdat)) |
| 3771 | return NODE_RECLAIM_FULL; |
| 3772 | |
| 3773 | /* |
| 3774 | * Do not scan if the allocation should not be delayed. |
| 3775 | */ |
| 3776 | if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC)) |
| 3777 | return NODE_RECLAIM_NOSCAN; |
| 3778 | |
| 3779 | /* |
| 3780 | * Only run node reclaim on the local node or on nodes that do not |
| 3781 | * have associated processors. This will favor the local processor |
| 3782 | * over remote processors and spread off node memory allocations |
| 3783 | * as wide as possible. |
| 3784 | */ |
| 3785 | if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id()) |
| 3786 | return NODE_RECLAIM_NOSCAN; |
| 3787 | |
| 3788 | if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags)) |
| 3789 | return NODE_RECLAIM_NOSCAN; |
| 3790 | |
| 3791 | ret = __node_reclaim(pgdat, gfp_mask, order); |
| 3792 | clear_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags); |
| 3793 | |
| 3794 | if (!ret) |
| 3795 | count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); |
| 3796 | |
| 3797 | return ret; |
| 3798 | } |
| 3799 | #endif |
| 3800 | |
| 3801 | /* |
| 3802 | * page_evictable - test whether a page is evictable |
| 3803 | * @page: the page to test |
| 3804 | * |
| 3805 | * Test whether page is evictable--i.e., should be placed on active/inactive |
| 3806 | * lists vs unevictable list. |
| 3807 | * |
| 3808 | * Reasons page might not be evictable: |
| 3809 | * (1) page's mapping marked unevictable |
| 3810 | * (2) page is part of an mlocked VMA |
| 3811 | * |
| 3812 | */ |
| 3813 | int page_evictable(struct page *page) |
| 3814 | { |
| 3815 | return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page); |
| 3816 | } |
| 3817 | |
| 3818 | #ifdef CONFIG_SHMEM |
| 3819 | /** |
| 3820 | * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list |
| 3821 | * @pages: array of pages to check |
| 3822 | * @nr_pages: number of pages to check |
| 3823 | * |
| 3824 | * Checks pages for evictability and moves them to the appropriate lru list. |
| 3825 | * |
| 3826 | * This function is only used for SysV IPC SHM_UNLOCK. |
| 3827 | */ |
| 3828 | void check_move_unevictable_pages(struct page **pages, int nr_pages) |
| 3829 | { |
| 3830 | struct lruvec *lruvec; |
| 3831 | struct pglist_data *pgdat = NULL; |
| 3832 | int pgscanned = 0; |
| 3833 | int pgrescued = 0; |
| 3834 | int i; |
| 3835 | |
| 3836 | for (i = 0; i < nr_pages; i++) { |
| 3837 | struct page *page = pages[i]; |
| 3838 | struct pglist_data *pagepgdat = page_pgdat(page); |
| 3839 | |
| 3840 | pgscanned++; |
| 3841 | if (pagepgdat != pgdat) { |
| 3842 | if (pgdat) |
| 3843 | spin_unlock_irq(&pgdat->lru_lock); |
| 3844 | pgdat = pagepgdat; |
| 3845 | spin_lock_irq(&pgdat->lru_lock); |
| 3846 | } |
| 3847 | lruvec = mem_cgroup_page_lruvec(page, pgdat); |
| 3848 | |
| 3849 | if (!PageLRU(page) || !PageUnevictable(page)) |
| 3850 | continue; |
| 3851 | |
| 3852 | if (page_evictable(page)) { |
| 3853 | enum lru_list lru = page_lru_base_type(page); |
| 3854 | |
| 3855 | VM_BUG_ON_PAGE(PageActive(page), page); |
| 3856 | ClearPageUnevictable(page); |
| 3857 | del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE); |
| 3858 | add_page_to_lru_list(page, lruvec, lru); |
| 3859 | pgrescued++; |
| 3860 | } |
| 3861 | } |
| 3862 | |
| 3863 | if (pgdat) { |
| 3864 | __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued); |
| 3865 | __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned); |
| 3866 | spin_unlock_irq(&pgdat->lru_lock); |
| 3867 | } |
| 3868 | } |
| 3869 | #endif /* CONFIG_SHMEM */ |