mm/compaction.c

   1 /*
   2  * linux/mm/compaction.c
   3  *
   4  * Memory compaction for the reduction of external fragmentation. Note that
   5  * this heavily depends upon page migration to do all the real heavy
   6  * lifting
   7  *
   8  * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
   9  */
  10 #include <linux/swap.h>
  11 #include <linux/migrate.h>
  12 #include <linux/compaction.h>
  13 #include <linux/mm_inline.h>
  14 #include <linux/backing-dev.h>
  15 #include <linux/sysctl.h>
  16 #include <linux/sysfs.h>
  17 #include "internal.h"
  18
  19 #define CREATE_TRACE_POINTS
  20 #include <trace/events/compaction.h>
  21
  22 /*
  23  * compact_control is used to track pages being migrated and the free pages
  24  * they are being migrated to during memory compaction. The free_pfn starts
  25  * at the end of a zone and migrate_pfn begins at the start. Movable pages
  26  * are moved to the end of a zone during a compaction run and the run
  27  * completes when free_pfn <= migrate_pfn
  28  */
  29 struct compact_control {
  30         struct list_head freepages;     /* List of free pages to migrate to */
  31         struct list_head migratepages;  /* List of pages being migrated */
  32         unsigned long nr_freepages;     /* Number of isolated free pages */
  33         unsigned long nr_migratepages;  /* Number of pages to migrate */
  34         unsigned long free_pfn;         /* isolate_freepages search base */
  35         unsigned long migrate_pfn;      /* isolate_migratepages search base */
  36         bool sync;                      /* Synchronous migration */
  37
  38         unsigned int order;             /* order a direct compactor needs */
  39         int migratetype;                /* MOVABLE, RECLAIMABLE etc */
  40         struct zone *zone;
  41 };
  42
  43 static unsigned long release_freepages(struct list_head *freelist)
  44 {
  45         struct page *page, *next;
  46         unsigned long count = 0;
  47
  48         list_for_each_entry_safe(page, next, freelist, lru) {
  49                 list_del(&page->lru);
  50                 __free_page(page);
  51                 count++;
  52         }
  53
  54         return count;
  55 }
  56
  57 /* Isolate free pages onto a private freelist. Must hold zone->lock */
  58 static unsigned long isolate_freepages_block(struct zone *zone,
  59                                 unsigned long blockpfn,
  60                                 struct list_head *freelist)
  61 {
  62         unsigned long zone_end_pfn, end_pfn;
  63         int nr_scanned = 0, total_isolated = 0;
  64         struct page *cursor;
  65
  66         /* Get the last PFN we should scan for free pages at */
  67         zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
  68         end_pfn = min(blockpfn + pageblock_nr_pages, zone_end_pfn);
  69
  70         /* Find the first usable PFN in the block to initialse page cursor */
  71         for (; blockpfn < end_pfn; blockpfn++) {
  72                 if (pfn_valid_within(blockpfn))
  73                         break;
  74         }
  75         cursor = pfn_to_page(blockpfn);
  76
  77         /* Isolate free pages. This assumes the block is valid */
  78         for (; blockpfn < end_pfn; blockpfn++, cursor++) {
  79                 int isolated, i;
  80                 struct page *page = cursor;
  81
  82                 if (!pfn_valid_within(blockpfn))
  83                         continue;
  84                 nr_scanned++;
  85
  86                 if (!PageBuddy(page))
  87                         continue;
  88
  89                 /* Found a free page, break it into order-0 pages */
  90                 isolated = split_free_page(page);
  91                 total_isolated += isolated;
  92                 for (i = 0; i < isolated; i++) {
  93                         list_add(&page->lru, freelist);
  94                         page++;
  95                 }
  96
  97                 /* If a page was split, advance to the end of it */
  98                 if (isolated) {
  99                         blockpfn += isolated - 1;
 100                         cursor += isolated - 1;
 101                 }
 102         }
 103
 104         trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated);
 105         return total_isolated;
 106 }
 107
 108 /* Returns true if the page is within a block suitable for migration to */
 109 static bool suitable_migration_target(struct page *page)
 110 {
 111
 112         int migratetype = get_pageblock_migratetype(page);
 113
 114         /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
 115         if (migratetype == MIGRATE_ISOLATE || migratetype == MIGRATE_RESERVE)
 116                 return false;
 117
 118         /* If the page is a large free page, then allow migration */
 119         if (PageBuddy(page) && page_order(page) >= pageblock_order)
 120                 return true;
 121
 122         /* If the block is MIGRATE_MOVABLE, allow migration */
 123         if (migratetype == MIGRATE_MOVABLE)
 124                 return true;
 125
 126         /* Otherwise skip the block */
 127         return false;
 128 }
 129
 130 /*
 131  * Based on information in the current compact_control, find blocks
 132  * suitable for isolating free pages from and then isolate them.
 133  */
 134 static void isolate_freepages(struct zone *zone,
 135                                 struct compact_control *cc)
 136 {
 137         struct page *page;
 138         unsigned long high_pfn, low_pfn, pfn;
 139         unsigned long flags;
 140         int nr_freepages = cc->nr_freepages;
 141         struct list_head *freelist = &cc->freepages;
 142
 143         /*
 144          * Initialise the free scanner. The starting point is where we last
 145          * scanned from (or the end of the zone if starting). The low point
 146          * is the end of the pageblock the migration scanner is using.
 147          */
 148         pfn = cc->free_pfn;
 149         low_pfn = cc->migrate_pfn + pageblock_nr_pages;
 150
 151         /*
 152          * Take care that if the migration scanner is at the end of the zone
 153          * that the free scanner does not accidentally move to the next zone
 154          * in the next isolation cycle.
 155          */
 156         high_pfn = min(low_pfn, pfn);
 157
 158         /*
 159          * Isolate free pages until enough are available to migrate the
 160          * pages on cc->migratepages. We stop searching if the migrate
 161          * and free page scanners meet or enough free pages are isolated.
 162          */
 163         for (; pfn > low_pfn && cc->nr_migratepages > nr_freepages;
 164                                         pfn -= pageblock_nr_pages) {
 165                 unsigned long isolated;
 166
 167                 if (!pfn_valid(pfn))
 168                         continue;
 169
 170                 /*
 171                  * Check for overlapping nodes/zones. It's possible on some
 172                  * configurations to have a setup like
 173                  * node0 node1 node0
 174                  * i.e. it's possible that all pages within a zones range of
 175                  * pages do not belong to a single zone.
 176                  */
 177                 page = pfn_to_page(pfn);
 178                 if (page_zone(page) != zone)
 179                         continue;
 180
 181                 /* Check the block is suitable for migration */
 182                 if (!suitable_migration_target(page))
 183                         continue;
 184
 185                 /*
 186                  * Found a block suitable for isolating free pages from. Now
 187                  * we disabled interrupts, double check things are ok and
 188                  * isolate the pages. This is to minimise the time IRQs
 189                  * are disabled
 190                  */
 191                 isolated = 0;
 192                 spin_lock_irqsave(&zone->lock, flags);
 193                 if (suitable_migration_target(page)) {
 194                         isolated = isolate_freepages_block(zone, pfn, freelist);
 195                         nr_freepages += isolated;
 196                 }
 197                 spin_unlock_irqrestore(&zone->lock, flags);
 198
 199                 /*
 200                  * Record the highest PFN we isolated pages from. When next
 201                  * looking for free pages, the search will restart here as
 202                  * page migration may have returned some pages to the allocator
 203                  */
 204                 if (isolated)
 205                         high_pfn = max(high_pfn, pfn);
 206         }
 207
 208         /* split_free_page does not map the pages */
 209         list_for_each_entry(page, freelist, lru) {
 210                 arch_alloc_page(page, 0);
 211                 kernel_map_pages(page, 1, 1);
 212         }
 213
 214         cc->free_pfn = high_pfn;
 215         cc->nr_freepages = nr_freepages;
 216 }
 217
 218 /* Update the number of anon and file isolated pages in the zone */
 219 static void acct_isolated(struct zone *zone, struct compact_control *cc)
 220 {
 221         struct page *page;
 222         unsigned int count[2] = { 0, };
 223
 224         list_for_each_entry(page, &cc->migratepages, lru)
 225                 count[!!page_is_file_cache(page)]++;
 226
 227         __mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
 228         __mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
 229 }
 230
 231 /* Similar to reclaim, but different enough that they don't share logic */
 232 static bool too_many_isolated(struct zone *zone)
 233 {
 234         unsigned long active, inactive, isolated;
 235
 236         inactive = zone_page_state(zone, NR_INACTIVE_FILE) +
 237                                         zone_page_state(zone, NR_INACTIVE_ANON);
 238         active = zone_page_state(zone, NR_ACTIVE_FILE) +
 239                                         zone_page_state(zone, NR_ACTIVE_ANON);
 240         isolated = zone_page_state(zone, NR_ISOLATED_FILE) +
 241                                         zone_page_state(zone, NR_ISOLATED_ANON);
 242
 243         return isolated > (inactive + active) / 2;
 244 }
 245
 246 /* possible outcome of isolate_migratepages */
 247 typedef enum {
 248         ISOLATE_ABORT,          /* Abort compaction now */
 249         ISOLATE_NONE,           /* No pages isolated, continue scanning */
 250         ISOLATE_SUCCESS,        /* Pages isolated, migrate */
 251 } isolate_migrate_t;
 252
 253 /*
 254  * Isolate all pages that can be migrated from the block pointed to by
 255  * the migrate scanner within compact_control.
 256  */
 257 static isolate_migrate_t isolate_migratepages(struct zone *zone,
 258                                         struct compact_control *cc)
 259 {
 260         unsigned long low_pfn, end_pfn;
 261         unsigned long last_pageblock_nr = 0, pageblock_nr;
 262         unsigned long nr_scanned = 0, nr_isolated = 0;
 263         struct list_head *migratelist = &cc->migratepages;
 264         isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE;
 265
 266         /* Do not scan outside zone boundaries */
 267         low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
 268
 269         /* Only scan within a pageblock boundary */
 270         end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
 271
 272         /* Do not cross the free scanner or scan within a memory hole */
 273         if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
 274                 cc->migrate_pfn = end_pfn;
 275                 return ISOLATE_NONE;
 276         }
 277
 278         /*
 279          * Ensure that there are not too many pages isolated from the LRU
 280          * list by either parallel reclaimers or compaction. If there are,
 281          * delay for some time until fewer pages are isolated
 282          */
 283         while (unlikely(too_many_isolated(zone))) {
 284                 /* async migration should just abort */
 285                 if (!cc->sync)
 286                         return ISOLATE_ABORT;
 287
 288                 congestion_wait(BLK_RW_ASYNC, HZ/10);
 289
 290                 if (fatal_signal_pending(current))
 291                         return ISOLATE_ABORT;
 292         }
 293
 294         /* Time to isolate some pages for migration */
 295         cond_resched();
 296         spin_lock_irq(&zone->lru_lock);
 297         for (; low_pfn < end_pfn; low_pfn++) {
 298                 struct page *page;
 299                 bool locked = true;
 300
 301                 /* give a chance to irqs before checking need_resched() */
 302                 if (!((low_pfn+1) % SWAP_CLUSTER_MAX)) {
 303                         spin_unlock_irq(&zone->lru_lock);
 304                         locked = false;
 305                 }
 306                 if (need_resched() || spin_is_contended(&zone->lru_lock)) {
 307                         if (locked)
 308                                 spin_unlock_irq(&zone->lru_lock);
 309                         cond_resched();
 310                         spin_lock_irq(&zone->lru_lock);
 311                         if (fatal_signal_pending(current))
 312                                 break;
 313                 } else if (!locked)
 314                         spin_lock_irq(&zone->lru_lock);
 315
 316                 if (!pfn_valid_within(low_pfn))
 317                         continue;
 318                 nr_scanned++;
 319
 320                 /* Get the page and skip if free */
 321                 page = pfn_to_page(low_pfn);
 322                 if (PageBuddy(page))
 323                         continue;
 324
 325                 /*
 326                  * For async migration, also only scan in MOVABLE blocks. Async
 327                  * migration is optimistic to see if the minimum amount of work
 328                  * satisfies the allocation
 329                  */
 330                 pageblock_nr = low_pfn >> pageblock_order;
 331                 if (!cc->sync && last_pageblock_nr != pageblock_nr &&
 332                                 get_pageblock_migratetype(page) != MIGRATE_MOVABLE) {
 333                         low_pfn += pageblock_nr_pages;
 334                         low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
 335                         last_pageblock_nr = pageblock_nr;
 336                         continue;
 337                 }
 338
 339                 if (!PageLRU(page))
 340                         continue;
 341
 342                 /*
 343                  * PageLRU is set, and lru_lock excludes isolation,
 344                  * splitting and collapsing (collapsing has already
 345                  * happened if PageLRU is set).
 346                  */
 347                 if (PageTransHuge(page)) {
 348                         low_pfn += (1 << compound_order(page)) - 1;
 349                         continue;
 350                 }
 351
 352                 if (!cc->sync)
 353                         mode |= ISOLATE_ASYNC_MIGRATE;
 354
 355                 /* Try isolate the page */
 356                 if (__isolate_lru_page(page, mode, 0) != 0)
 357                         continue;
 358
 359                 VM_BUG_ON(PageTransCompound(page));
 360
 361                 /* Successfully isolated */
 362                 del_page_from_lru_list(zone, page, page_lru(page));
 363                 list_add(&page->lru, migratelist);
 364                 cc->nr_migratepages++;
 365                 nr_isolated++;
 366
 367                 /* Avoid isolating too much */
 368                 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
 369                         ++low_pfn;
 370                         break;
 371                 }
 372         }
 373
 374         acct_isolated(zone, cc);
 375
 376         spin_unlock_irq(&zone->lru_lock);
 377         cc->migrate_pfn = low_pfn;
 378
 379         trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);
 380
 381         return ISOLATE_SUCCESS;
 382 }
 383
 384 /*
 385  * This is a migrate-callback that "allocates" freepages by taking pages
 386  * from the isolated freelists in the block we are migrating to.
 387  */
 388 static struct page *compaction_alloc(struct page *migratepage,
 389                                         unsigned long data,
 390                                         int **result)
 391 {
 392         struct compact_control *cc = (struct compact_control *)data;
 393         struct page *freepage;
 394
 395         /* Isolate free pages if necessary */
 396         if (list_empty(&cc->freepages)) {
 397                 isolate_freepages(cc->zone, cc);
 398
 399                 if (list_empty(&cc->freepages))
 400                         return NULL;
 401         }
 402
 403         freepage = list_entry(cc->freepages.next, struct page, lru);
 404         list_del(&freepage->lru);
 405         cc->nr_freepages--;
 406
 407         return freepage;
 408 }
 409
 410 /*
 411  * We cannot control nr_migratepages and nr_freepages fully when migration is
 412  * running as migrate_pages() has no knowledge of compact_control. When
 413  * migration is complete, we count the number of pages on the lists by hand.
 414  */
 415 static void update_nr_listpages(struct compact_control *cc)
 416 {
 417         int nr_migratepages = 0;
 418         int nr_freepages = 0;
 419         struct page *page;
 420
 421         list_for_each_entry(page, &cc->migratepages, lru)
 422                 nr_migratepages++;
 423         list_for_each_entry(page, &cc->freepages, lru)
 424                 nr_freepages++;
 425
 426         cc->nr_migratepages = nr_migratepages;
 427         cc->nr_freepages = nr_freepages;
 428 }
 429
 430 static int compact_finished(struct zone *zone,
 431                             struct compact_control *cc)
 432 {
 433         unsigned int order;
 434         unsigned long watermark;
 435
 436         if (fatal_signal_pending(current))
 437                 return COMPACT_PARTIAL;
 438
 439         /* Compaction run completes if the migrate and free scanner meet */
 440         if (cc->free_pfn <= cc->migrate_pfn)
 441                 return COMPACT_COMPLETE;
 442
 443         /*
 444          * order == -1 is expected when compacting via
 445          * /proc/sys/vm/compact_memory
 446          */
 447         if (cc->order == -1)
 448                 return COMPACT_CONTINUE;
 449
 450         /* Compaction run is not finished if the watermark is not met */
 451         watermark = low_wmark_pages(zone);
 452         watermark += (1 << cc->order);
 453
 454         if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
 455                 return COMPACT_CONTINUE;
 456
 457         /* Direct compactor: Is a suitable page free? */
 458         for (order = cc->order; order < MAX_ORDER; order++) {
 459                 /* Job done if page is free of the right migratetype */
 460                 if (!list_empty(&zone->free_area[order].free_list[cc->migratetype]))
 461                         return COMPACT_PARTIAL;
 462
 463                 /* Job done if allocation would set block type */
 464                 if (order >= pageblock_order && zone->free_area[order].nr_free)
 465                         return COMPACT_PARTIAL;
 466         }
 467
 468         return COMPACT_CONTINUE;
 469 }
 470
 471 /*
 472  * compaction_suitable: Is this suitable to run compaction on this zone now?
 473  * Returns
 474  *   COMPACT_SKIPPED  - If there are too few free pages for compaction
 475  *   COMPACT_PARTIAL  - If the allocation would succeed without compaction
 476  *   COMPACT_CONTINUE - If compaction should run now
 477  */
 478 unsigned long compaction_suitable(struct zone *zone, int order)
 479 {
 480         int fragindex;
 481         unsigned long watermark;
 482
 483         /*
 484          * order == -1 is expected when compacting via
 485          * /proc/sys/vm/compact_memory
 486          */
 487         if (order == -1)
 488                 return COMPACT_CONTINUE;
 489
 490         /*
 491          * Watermarks for order-0 must be met for compaction. Note the 2UL.
 492          * This is because during migration, copies of pages need to be
 493          * allocated and for a short time, the footprint is higher
 494          */
 495         watermark = low_wmark_pages(zone) + (2UL << order);
 496         if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
 497                 return COMPACT_SKIPPED;
 498
 499         /*
 500          * fragmentation index determines if allocation failures are due to
 501          * low memory or external fragmentation
 502          *
 503          * index of -1000 implies allocations might succeed depending on
 504          * watermarks
 505          * index towards 0 implies failure is due to lack of memory
 506          * index towards 1000 implies failure is due to fragmentation
 507          *
 508          * Only compact if a failure would be due to fragmentation.
 509          */
 510         fragindex = fragmentation_index(zone, order);
 511         if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
 512                 return COMPACT_SKIPPED;
 513
 514         if (fragindex == -1000 && zone_watermark_ok(zone, order, watermark,
 515             0, 0))
 516                 return COMPACT_PARTIAL;
 517
 518         return COMPACT_CONTINUE;
 519 }
 520
 521 static int compact_zone(struct zone *zone, struct compact_control *cc)
 522 {
 523         int ret;
 524
 525         ret = compaction_suitable(zone, cc->order);
 526         switch (ret) {
 527         case COMPACT_PARTIAL:
 528         case COMPACT_SKIPPED:
 529                 /* Compaction is likely to fail */
 530                 return ret;
 531         case COMPACT_CONTINUE:
 532                 /* Fall through to compaction */
 533                 ;
 534         }
 535
 536         /* Setup to move all movable pages to the end of the zone */
 537         cc->migrate_pfn = zone->zone_start_pfn;
 538         cc->free_pfn = cc->migrate_pfn + zone->spanned_pages;
 539         cc->free_pfn &= ~(pageblock_nr_pages-1);
 540
 541         migrate_prep_local();
 542
 543         while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
 544                 unsigned long nr_migrate, nr_remaining;
 545                 int err;
 546
 547                 switch (isolate_migratepages(zone, cc)) {
 548                 case ISOLATE_ABORT:
 549                         ret = COMPACT_PARTIAL;
 550                         goto out;
 551                 case ISOLATE_NONE:
 552                         continue;
 553                 case ISOLATE_SUCCESS:
 554                         ;
 555                 }
 556
 557                 nr_migrate = cc->nr_migratepages;
 558                 err = migrate_pages(&cc->migratepages, compaction_alloc,
 559                                 (unsigned long)cc, false,
 560                                 cc->sync ? MIGRATE_SYNC_LIGHT : MIGRATE_ASYNC);
 561                 update_nr_listpages(cc);
 562                 nr_remaining = cc->nr_migratepages;
 563
 564                 count_vm_event(COMPACTBLOCKS);
 565                 count_vm_events(COMPACTPAGES, nr_migrate - nr_remaining);
 566                 if (nr_remaining)
 567                         count_vm_events(COMPACTPAGEFAILED, nr_remaining);
 568                 trace_mm_compaction_migratepages(nr_migrate - nr_remaining,
 569                                                 nr_remaining);
 570
 571                 /* Release LRU pages not migrated */
 572                 if (err) {
 573                         putback_lru_pages(&cc->migratepages);
 574                         cc->nr_migratepages = 0;
 575                 }
 576
 577         }
 578
 579 out:
 580         /* Release free pages and check accounting */
 581         cc->nr_freepages -= release_freepages(&cc->freepages);
 582         VM_BUG_ON(cc->nr_freepages != 0);
 583
 584         return ret;
 585 }
 586
 587 static unsigned long compact_zone_order(struct zone *zone,
 588                                  int order, gfp_t gfp_mask,
 589                                  bool sync)
 590 {
 591         struct compact_control cc = {
 592                 .nr_freepages = 0,
 593                 .nr_migratepages = 0,
 594                 .order = order,
 595                 .migratetype = allocflags_to_migratetype(gfp_mask),
 596                 .zone = zone,
 597                 .sync = sync,
 598         };
 599         INIT_LIST_HEAD(&cc.freepages);
 600         INIT_LIST_HEAD(&cc.migratepages);
 601
 602         return compact_zone(zone, &cc);
 603 }
 604
 605 int sysctl_extfrag_threshold = 500;
 606
 607 /**
 608  * try_to_compact_pages - Direct compact to satisfy a high-order allocation
 609  * @zonelist: The zonelist used for the current allocation
 610  * @order: The order of the current allocation
 611  * @gfp_mask: The GFP mask of the current allocation
 612  * @nodemask: The allowed nodes to allocate from
 613  * @sync: Whether migration is synchronous or not
 614  *
 615  * This is the main entry point for direct page compaction.
 616  */
 617 unsigned long try_to_compact_pages(struct zonelist *zonelist,
 618                         int order, gfp_t gfp_mask, nodemask_t *nodemask,
 619                         bool sync)
 620 {
 621         enum zone_type high_zoneidx = gfp_zone(gfp_mask);
 622         int may_enter_fs = gfp_mask & __GFP_FS;
 623         int may_perform_io = gfp_mask & __GFP_IO;
 624         struct zoneref *z;
 625         struct zone *zone;
 626         int rc = COMPACT_SKIPPED;
 627
 628         /*
 629          * Check whether it is worth even starting compaction. The order check is
 630          * made because an assumption is made that the page allocator can satisfy
 631          * the "cheaper" orders without taking special steps
 632          */
 633         if (!order || !may_enter_fs || !may_perform_io)
 634                 return rc;
 635
 636         count_vm_event(COMPACTSTALL);
 637
 638         /* Compact each zone in the list */
 639         for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
 640                                                                 nodemask) {
 641                 int status;
 642
 643                 status = compact_zone_order(zone, order, gfp_mask, sync);
 644                 rc = max(status, rc);
 645
 646                 /* If a normal allocation would succeed, stop compacting */
 647                 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
 648                         break;
 649         }
 650
 651         return rc;
 652 }
 653
 654
 655 /* Compact all zones within a node */
 656 static int compact_node(int nid)
 657 {
 658         int zoneid;
 659         pg_data_t *pgdat;
 660         struct zone *zone;
 661
 662         if (nid < 0 || nid >= nr_node_ids || !node_online(nid))
 663                 return -EINVAL;
 664         pgdat = NODE_DATA(nid);
 665
 666         /* Flush pending updates to the LRU lists */
 667         lru_add_drain_all();
 668
 669         for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
 670                 struct compact_control cc = {
 671                         .nr_freepages = 0,
 672                         .nr_migratepages = 0,
 673                         .order = -1,
 674                         .sync = true,
 675                 };
 676
 677                 zone = &pgdat->node_zones[zoneid];
 678                 if (!populated_zone(zone))
 679                         continue;
 680
 681                 cc.zone = zone;
 682                 INIT_LIST_HEAD(&cc.freepages);
 683                 INIT_LIST_HEAD(&cc.migratepages);
 684
 685                 compact_zone(zone, &cc);
 686
 687                 VM_BUG_ON(!list_empty(&cc.freepages));
 688                 VM_BUG_ON(!list_empty(&cc.migratepages));
 689         }
 690
 691         return 0;
 692 }
 693
 694 /* Compact all nodes in the system */
 695 static int compact_nodes(void)
 696 {
 697         int nid;
 698
 699         for_each_online_node(nid)
 700                 compact_node(nid);
 701
 702         return COMPACT_COMPLETE;
 703 }
 704
 705 /* The written value is actually unused, all memory is compacted */
 706 int sysctl_compact_memory;
 707
 708 /* This is the entry point for compacting all nodes via /proc/sys/vm */
 709 int sysctl_compaction_handler(struct ctl_table *table, int write,
 710                         void __user *buffer, size_t *length, loff_t *ppos)
 711 {
 712         if (write)
 713                 return compact_nodes();
 714
 715         return 0;
 716 }
 717
 718 int sysctl_extfrag_handler(struct ctl_table *table, int write,
 719                         void __user *buffer, size_t *length, loff_t *ppos)
 720 {
 721         proc_dointvec_minmax(table, write, buffer, length, ppos);
 722
 723         return 0;
 724 }
 725
 726 #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 727 ssize_t sysfs_compact_node(struct device *dev,
 728                         struct device_attribute *attr,
 729                         const char *buf, size_t count)
 730 {
 731         compact_node(dev->id);
 732
 733         return count;
 734 }
 735 static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
 736
 737 int compaction_register_node(struct node *node)
 738 {
 739         return device_create_file(&node->dev, &dev_attr_compact);
 740 }
 741
 742 void compaction_unregister_node(struct node *node)
 743 {
 744         return device_remove_file(&node->dev, &dev_attr_compact);
 745 }
 746 #endif /* CONFIG_SYSFS && CONFIG_NUMA */