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1da177e4 LT |
1 | /* |
2 | * linux/mm/oom_kill.c | |
3 | * | |
4 | * Copyright (C) 1998,2000 Rik van Riel | |
5 | * Thanks go out to Claus Fischer for some serious inspiration and | |
6 | * for goading me into coding this file... | |
7 | * | |
8 | * The routines in this file are used to kill a process when | |
a49335cc PJ |
9 | * we're seriously out of memory. This gets called from __alloc_pages() |
10 | * in mm/page_alloc.c when we really run out of memory. | |
1da177e4 LT |
11 | * |
12 | * Since we won't call these routines often (on a well-configured | |
13 | * machine) this file will double as a 'coding guide' and a signpost | |
14 | * for newbie kernel hackers. It features several pointers to major | |
15 | * kernel subsystems and hints as to where to find out what things do. | |
16 | */ | |
17 | ||
18 | #include <linux/mm.h> | |
19 | #include <linux/sched.h> | |
20 | #include <linux/swap.h> | |
21 | #include <linux/timex.h> | |
22 | #include <linux/jiffies.h> | |
ef08e3b4 | 23 | #include <linux/cpuset.h> |
1da177e4 LT |
24 | |
25 | /* #define DEBUG */ | |
26 | ||
27 | /** | |
28 | * oom_badness - calculate a numeric value for how bad this task has been | |
29 | * @p: task struct of which task we should calculate | |
a49335cc | 30 | * @uptime: current uptime in seconds |
1da177e4 LT |
31 | * |
32 | * The formula used is relatively simple and documented inline in the | |
33 | * function. The main rationale is that we want to select a good task | |
34 | * to kill when we run out of memory. | |
35 | * | |
36 | * Good in this context means that: | |
37 | * 1) we lose the minimum amount of work done | |
38 | * 2) we recover a large amount of memory | |
39 | * 3) we don't kill anything innocent of eating tons of memory | |
40 | * 4) we want to kill the minimum amount of processes (one) | |
41 | * 5) we try to kill the process the user expects us to kill, this | |
42 | * algorithm has been meticulously tuned to meet the principle | |
43 | * of least surprise ... (be careful when you change it) | |
44 | */ | |
45 | ||
46 | unsigned long badness(struct task_struct *p, unsigned long uptime) | |
47 | { | |
48 | unsigned long points, cpu_time, run_time, s; | |
97c2c9b8 AM |
49 | struct mm_struct *mm; |
50 | struct task_struct *child; | |
1da177e4 | 51 | |
97c2c9b8 AM |
52 | task_lock(p); |
53 | mm = p->mm; | |
54 | if (!mm) { | |
55 | task_unlock(p); | |
1da177e4 | 56 | return 0; |
97c2c9b8 | 57 | } |
1da177e4 LT |
58 | |
59 | /* | |
60 | * The memory size of the process is the basis for the badness. | |
61 | */ | |
97c2c9b8 AM |
62 | points = mm->total_vm; |
63 | ||
64 | /* | |
65 | * After this unlock we can no longer dereference local variable `mm' | |
66 | */ | |
67 | task_unlock(p); | |
1da177e4 LT |
68 | |
69 | /* | |
70 | * Processes which fork a lot of child processes are likely | |
9827b781 | 71 | * a good choice. We add half the vmsize of the children if they |
1da177e4 | 72 | * have an own mm. This prevents forking servers to flood the |
9827b781 KG |
73 | * machine with an endless amount of children. In case a single |
74 | * child is eating the vast majority of memory, adding only half | |
75 | * to the parents will make the child our kill candidate of choice. | |
1da177e4 | 76 | */ |
97c2c9b8 AM |
77 | list_for_each_entry(child, &p->children, sibling) { |
78 | task_lock(child); | |
79 | if (child->mm != mm && child->mm) | |
80 | points += child->mm->total_vm/2 + 1; | |
81 | task_unlock(child); | |
1da177e4 LT |
82 | } |
83 | ||
84 | /* | |
85 | * CPU time is in tens of seconds and run time is in thousands | |
86 | * of seconds. There is no particular reason for this other than | |
87 | * that it turned out to work very well in practice. | |
88 | */ | |
89 | cpu_time = (cputime_to_jiffies(p->utime) + cputime_to_jiffies(p->stime)) | |
90 | >> (SHIFT_HZ + 3); | |
91 | ||
92 | if (uptime >= p->start_time.tv_sec) | |
93 | run_time = (uptime - p->start_time.tv_sec) >> 10; | |
94 | else | |
95 | run_time = 0; | |
96 | ||
97 | s = int_sqrt(cpu_time); | |
98 | if (s) | |
99 | points /= s; | |
100 | s = int_sqrt(int_sqrt(run_time)); | |
101 | if (s) | |
102 | points /= s; | |
103 | ||
104 | /* | |
105 | * Niced processes are most likely less important, so double | |
106 | * their badness points. | |
107 | */ | |
108 | if (task_nice(p) > 0) | |
109 | points *= 2; | |
110 | ||
111 | /* | |
112 | * Superuser processes are usually more important, so we make it | |
113 | * less likely that we kill those. | |
114 | */ | |
115 | if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_ADMIN) || | |
116 | p->uid == 0 || p->euid == 0) | |
117 | points /= 4; | |
118 | ||
119 | /* | |
120 | * We don't want to kill a process with direct hardware access. | |
121 | * Not only could that mess up the hardware, but usually users | |
122 | * tend to only have this flag set on applications they think | |
123 | * of as important. | |
124 | */ | |
125 | if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_RAWIO)) | |
126 | points /= 4; | |
127 | ||
128 | /* | |
129 | * Adjust the score by oomkilladj. | |
130 | */ | |
131 | if (p->oomkilladj) { | |
132 | if (p->oomkilladj > 0) | |
133 | points <<= p->oomkilladj; | |
134 | else | |
135 | points >>= -(p->oomkilladj); | |
136 | } | |
137 | ||
138 | #ifdef DEBUG | |
139 | printk(KERN_DEBUG "OOMkill: task %d (%s) got %d points\n", | |
140 | p->pid, p->comm, points); | |
141 | #endif | |
142 | return points; | |
143 | } | |
144 | ||
9b0f8b04 CL |
145 | /* |
146 | * Types of limitations to the nodes from which allocations may occur | |
147 | */ | |
148 | #define CONSTRAINT_NONE 1 | |
149 | #define CONSTRAINT_MEMORY_POLICY 2 | |
150 | #define CONSTRAINT_CPUSET 3 | |
151 | ||
152 | /* | |
153 | * Determine the type of allocation constraint. | |
154 | */ | |
155 | static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask) | |
156 | { | |
157 | #ifdef CONFIG_NUMA | |
158 | struct zone **z; | |
159 | nodemask_t nodes = node_online_map; | |
160 | ||
161 | for (z = zonelist->zones; *z; z++) | |
162 | if (cpuset_zone_allowed(*z, gfp_mask)) | |
163 | node_clear((*z)->zone_pgdat->node_id, | |
164 | nodes); | |
165 | else | |
166 | return CONSTRAINT_CPUSET; | |
167 | ||
168 | if (!nodes_empty(nodes)) | |
169 | return CONSTRAINT_MEMORY_POLICY; | |
170 | #endif | |
171 | ||
172 | return CONSTRAINT_NONE; | |
173 | } | |
174 | ||
1da177e4 LT |
175 | /* |
176 | * Simple selection loop. We chose the process with the highest | |
177 | * number of 'points'. We expect the caller will lock the tasklist. | |
178 | * | |
179 | * (not docbooked, we don't want this one cluttering up the manual) | |
180 | */ | |
9827b781 | 181 | static struct task_struct *select_bad_process(unsigned long *ppoints) |
1da177e4 | 182 | { |
1da177e4 LT |
183 | struct task_struct *g, *p; |
184 | struct task_struct *chosen = NULL; | |
185 | struct timespec uptime; | |
9827b781 | 186 | *ppoints = 0; |
1da177e4 LT |
187 | |
188 | do_posix_clock_monotonic_gettime(&uptime); | |
a49335cc PJ |
189 | do_each_thread(g, p) { |
190 | unsigned long points; | |
191 | int releasing; | |
192 | ||
1da177e4 | 193 | /* skip the init task with pid == 1 */ |
a49335cc PJ |
194 | if (p->pid == 1) |
195 | continue; | |
196 | if (p->oomkilladj == OOM_DISABLE) | |
197 | continue; | |
ef08e3b4 PJ |
198 | /* If p's nodes don't overlap ours, it won't help to kill p. */ |
199 | if (!cpuset_excl_nodes_overlap(p)) | |
200 | continue; | |
201 | ||
a49335cc PJ |
202 | /* |
203 | * This is in the process of releasing memory so for wait it | |
204 | * to finish before killing some other task by mistake. | |
205 | */ | |
206 | releasing = test_tsk_thread_flag(p, TIF_MEMDIE) || | |
207 | p->flags & PF_EXITING; | |
208 | if (releasing && !(p->flags & PF_DEAD)) | |
209 | return ERR_PTR(-1UL); | |
210 | if (p->flags & PF_SWAPOFF) | |
211 | return p; | |
212 | ||
213 | points = badness(p, uptime.tv_sec); | |
9827b781 | 214 | if (points > *ppoints || !chosen) { |
a49335cc | 215 | chosen = p; |
9827b781 | 216 | *ppoints = points; |
1da177e4 | 217 | } |
a49335cc | 218 | } while_each_thread(g, p); |
1da177e4 LT |
219 | return chosen; |
220 | } | |
221 | ||
222 | /** | |
223 | * We must be careful though to never send SIGKILL a process with | |
224 | * CAP_SYS_RAW_IO set, send SIGTERM instead (but it's unlikely that | |
225 | * we select a process with CAP_SYS_RAW_IO set). | |
226 | */ | |
9b0f8b04 | 227 | static void __oom_kill_task(task_t *p, const char *message) |
1da177e4 LT |
228 | { |
229 | if (p->pid == 1) { | |
230 | WARN_ON(1); | |
231 | printk(KERN_WARNING "tried to kill init!\n"); | |
232 | return; | |
233 | } | |
234 | ||
235 | task_lock(p); | |
236 | if (!p->mm || p->mm == &init_mm) { | |
237 | WARN_ON(1); | |
238 | printk(KERN_WARNING "tried to kill an mm-less task!\n"); | |
239 | task_unlock(p); | |
240 | return; | |
241 | } | |
242 | task_unlock(p); | |
9b0f8b04 CL |
243 | printk(KERN_ERR "%s: Killed process %d (%s).\n", |
244 | message, p->pid, p->comm); | |
1da177e4 LT |
245 | |
246 | /* | |
247 | * We give our sacrificial lamb high priority and access to | |
248 | * all the memory it needs. That way it should be able to | |
249 | * exit() and clear out its resources quickly... | |
250 | */ | |
251 | p->time_slice = HZ; | |
252 | set_tsk_thread_flag(p, TIF_MEMDIE); | |
253 | ||
254 | force_sig(SIGKILL, p); | |
255 | } | |
256 | ||
9b0f8b04 | 257 | static struct mm_struct *oom_kill_task(task_t *p, const char *message) |
1da177e4 LT |
258 | { |
259 | struct mm_struct *mm = get_task_mm(p); | |
260 | task_t * g, * q; | |
261 | ||
262 | if (!mm) | |
263 | return NULL; | |
264 | if (mm == &init_mm) { | |
265 | mmput(mm); | |
266 | return NULL; | |
267 | } | |
268 | ||
9b0f8b04 | 269 | __oom_kill_task(p, message); |
1da177e4 LT |
270 | /* |
271 | * kill all processes that share the ->mm (i.e. all threads), | |
272 | * but are in a different thread group | |
273 | */ | |
274 | do_each_thread(g, q) | |
275 | if (q->mm == mm && q->tgid != p->tgid) | |
9b0f8b04 | 276 | __oom_kill_task(q, message); |
1da177e4 LT |
277 | while_each_thread(g, q); |
278 | ||
279 | return mm; | |
280 | } | |
281 | ||
9827b781 | 282 | static struct mm_struct *oom_kill_process(struct task_struct *p, |
9b0f8b04 | 283 | unsigned long points, const char *message) |
1da177e4 LT |
284 | { |
285 | struct mm_struct *mm; | |
286 | struct task_struct *c; | |
287 | struct list_head *tsk; | |
288 | ||
9827b781 KG |
289 | printk(KERN_ERR "Out of Memory: Kill process %d (%s) score %li and " |
290 | "children.\n", p->pid, p->comm, points); | |
1da177e4 LT |
291 | /* Try to kill a child first */ |
292 | list_for_each(tsk, &p->children) { | |
293 | c = list_entry(tsk, struct task_struct, sibling); | |
294 | if (c->mm == p->mm) | |
295 | continue; | |
9b0f8b04 | 296 | mm = oom_kill_task(c, message); |
1da177e4 LT |
297 | if (mm) |
298 | return mm; | |
299 | } | |
9b0f8b04 | 300 | return oom_kill_task(p, message); |
1da177e4 LT |
301 | } |
302 | ||
303 | /** | |
304 | * oom_kill - kill the "best" process when we run out of memory | |
305 | * | |
306 | * If we run out of memory, we have the choice between either | |
307 | * killing a random task (bad), letting the system crash (worse) | |
308 | * OR try to be smart about which process to kill. Note that we | |
309 | * don't have to be perfect here, we just have to be good. | |
310 | */ | |
9b0f8b04 | 311 | void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order) |
1da177e4 LT |
312 | { |
313 | struct mm_struct *mm = NULL; | |
9b0f8b04 | 314 | task_t *p; |
d6713e04 | 315 | unsigned long points = 0; |
1da177e4 | 316 | |
42639269 AB |
317 | if (printk_ratelimit()) { |
318 | printk("oom-killer: gfp_mask=0x%x, order=%d\n", | |
319 | gfp_mask, order); | |
b958f7d9 | 320 | dump_stack(); |
42639269 AB |
321 | show_mem(); |
322 | } | |
578c2fd6 | 323 | |
505970b9 | 324 | cpuset_lock(); |
1da177e4 | 325 | read_lock(&tasklist_lock); |
9b0f8b04 CL |
326 | |
327 | /* | |
328 | * Check if there were limitations on the allocation (only relevant for | |
329 | * NUMA) that may require different handling. | |
330 | */ | |
331 | switch (constrained_alloc(zonelist, gfp_mask)) { | |
332 | case CONSTRAINT_MEMORY_POLICY: | |
333 | mm = oom_kill_process(current, points, | |
334 | "No available memory (MPOL_BIND)"); | |
335 | break; | |
336 | ||
337 | case CONSTRAINT_CPUSET: | |
338 | mm = oom_kill_process(current, points, | |
339 | "No available memory in cpuset"); | |
340 | break; | |
341 | ||
342 | case CONSTRAINT_NONE: | |
1da177e4 | 343 | retry: |
9b0f8b04 CL |
344 | /* |
345 | * Rambo mode: Shoot down a process and hope it solves whatever | |
346 | * issues we may have. | |
347 | */ | |
348 | p = select_bad_process(&points); | |
1da177e4 | 349 | |
9b0f8b04 CL |
350 | if (PTR_ERR(p) == -1UL) |
351 | goto out; | |
1da177e4 | 352 | |
9b0f8b04 CL |
353 | /* Found nothing?!?! Either we hang forever, or we panic. */ |
354 | if (!p) { | |
355 | read_unlock(&tasklist_lock); | |
356 | cpuset_unlock(); | |
357 | panic("Out of memory and no killable processes...\n"); | |
358 | } | |
1da177e4 | 359 | |
9b0f8b04 CL |
360 | mm = oom_kill_process(p, points, "Out of memory"); |
361 | if (!mm) | |
362 | goto retry; | |
363 | ||
364 | break; | |
365 | } | |
1da177e4 | 366 | |
9b0f8b04 | 367 | out: |
140ffcec | 368 | read_unlock(&tasklist_lock); |
505970b9 | 369 | cpuset_unlock(); |
1da177e4 LT |
370 | if (mm) |
371 | mmput(mm); | |
372 | ||
373 | /* | |
374 | * Give "p" a good chance of killing itself before we | |
2f659f46 | 375 | * retry to allocate memory unless "p" is current |
1da177e4 | 376 | */ |
2f659f46 | 377 | if (!test_thread_flag(TIF_MEMDIE)) |
140ffcec | 378 | schedule_timeout_uninterruptible(1); |
1da177e4 | 379 | } |