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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> |
8bc719d3 MS |
24 | #include <linux/module.h> |
25 | #include <linux/notifier.h> | |
1da177e4 | 26 | |
fadd8fbd | 27 | int sysctl_panic_on_oom; |
1da177e4 LT |
28 | /* #define DEBUG */ |
29 | ||
30 | /** | |
6937a25c | 31 | * badness - calculate a numeric value for how bad this task has been |
1da177e4 | 32 | * @p: task struct of which task we should calculate |
a49335cc | 33 | * @uptime: current uptime in seconds |
1da177e4 LT |
34 | * |
35 | * The formula used is relatively simple and documented inline in the | |
36 | * function. The main rationale is that we want to select a good task | |
37 | * to kill when we run out of memory. | |
38 | * | |
39 | * Good in this context means that: | |
40 | * 1) we lose the minimum amount of work done | |
41 | * 2) we recover a large amount of memory | |
42 | * 3) we don't kill anything innocent of eating tons of memory | |
43 | * 4) we want to kill the minimum amount of processes (one) | |
44 | * 5) we try to kill the process the user expects us to kill, this | |
45 | * algorithm has been meticulously tuned to meet the principle | |
46 | * of least surprise ... (be careful when you change it) | |
47 | */ | |
48 | ||
49 | unsigned long badness(struct task_struct *p, unsigned long uptime) | |
50 | { | |
51 | unsigned long points, cpu_time, run_time, s; | |
97c2c9b8 AM |
52 | struct mm_struct *mm; |
53 | struct task_struct *child; | |
1da177e4 | 54 | |
97c2c9b8 AM |
55 | task_lock(p); |
56 | mm = p->mm; | |
57 | if (!mm) { | |
58 | task_unlock(p); | |
1da177e4 | 59 | return 0; |
97c2c9b8 | 60 | } |
1da177e4 LT |
61 | |
62 | /* | |
63 | * The memory size of the process is the basis for the badness. | |
64 | */ | |
97c2c9b8 AM |
65 | points = mm->total_vm; |
66 | ||
67 | /* | |
68 | * After this unlock we can no longer dereference local variable `mm' | |
69 | */ | |
70 | task_unlock(p); | |
1da177e4 LT |
71 | |
72 | /* | |
73 | * Processes which fork a lot of child processes are likely | |
9827b781 | 74 | * a good choice. We add half the vmsize of the children if they |
1da177e4 | 75 | * have an own mm. This prevents forking servers to flood the |
9827b781 KG |
76 | * machine with an endless amount of children. In case a single |
77 | * child is eating the vast majority of memory, adding only half | |
78 | * to the parents will make the child our kill candidate of choice. | |
1da177e4 | 79 | */ |
97c2c9b8 AM |
80 | list_for_each_entry(child, &p->children, sibling) { |
81 | task_lock(child); | |
82 | if (child->mm != mm && child->mm) | |
83 | points += child->mm->total_vm/2 + 1; | |
84 | task_unlock(child); | |
1da177e4 LT |
85 | } |
86 | ||
87 | /* | |
88 | * CPU time is in tens of seconds and run time is in thousands | |
89 | * of seconds. There is no particular reason for this other than | |
90 | * that it turned out to work very well in practice. | |
91 | */ | |
92 | cpu_time = (cputime_to_jiffies(p->utime) + cputime_to_jiffies(p->stime)) | |
93 | >> (SHIFT_HZ + 3); | |
94 | ||
95 | if (uptime >= p->start_time.tv_sec) | |
96 | run_time = (uptime - p->start_time.tv_sec) >> 10; | |
97 | else | |
98 | run_time = 0; | |
99 | ||
100 | s = int_sqrt(cpu_time); | |
101 | if (s) | |
102 | points /= s; | |
103 | s = int_sqrt(int_sqrt(run_time)); | |
104 | if (s) | |
105 | points /= s; | |
106 | ||
107 | /* | |
108 | * Niced processes are most likely less important, so double | |
109 | * their badness points. | |
110 | */ | |
111 | if (task_nice(p) > 0) | |
112 | points *= 2; | |
113 | ||
114 | /* | |
115 | * Superuser processes are usually more important, so we make it | |
116 | * less likely that we kill those. | |
117 | */ | |
118 | if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_ADMIN) || | |
119 | p->uid == 0 || p->euid == 0) | |
120 | points /= 4; | |
121 | ||
122 | /* | |
123 | * We don't want to kill a process with direct hardware access. | |
124 | * Not only could that mess up the hardware, but usually users | |
125 | * tend to only have this flag set on applications they think | |
126 | * of as important. | |
127 | */ | |
128 | if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_RAWIO)) | |
129 | points /= 4; | |
130 | ||
7887a3da NP |
131 | /* |
132 | * If p's nodes don't overlap ours, it may still help to kill p | |
133 | * because p may have allocated or otherwise mapped memory on | |
134 | * this node before. However it will be less likely. | |
135 | */ | |
136 | if (!cpuset_excl_nodes_overlap(p)) | |
137 | points /= 8; | |
138 | ||
1da177e4 LT |
139 | /* |
140 | * Adjust the score by oomkilladj. | |
141 | */ | |
142 | if (p->oomkilladj) { | |
143 | if (p->oomkilladj > 0) | |
144 | points <<= p->oomkilladj; | |
145 | else | |
146 | points >>= -(p->oomkilladj); | |
147 | } | |
148 | ||
149 | #ifdef DEBUG | |
150 | printk(KERN_DEBUG "OOMkill: task %d (%s) got %d points\n", | |
151 | p->pid, p->comm, points); | |
152 | #endif | |
153 | return points; | |
154 | } | |
155 | ||
9b0f8b04 CL |
156 | /* |
157 | * Types of limitations to the nodes from which allocations may occur | |
158 | */ | |
159 | #define CONSTRAINT_NONE 1 | |
160 | #define CONSTRAINT_MEMORY_POLICY 2 | |
161 | #define CONSTRAINT_CPUSET 3 | |
162 | ||
163 | /* | |
164 | * Determine the type of allocation constraint. | |
165 | */ | |
166 | static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask) | |
167 | { | |
168 | #ifdef CONFIG_NUMA | |
169 | struct zone **z; | |
170 | nodemask_t nodes = node_online_map; | |
171 | ||
172 | for (z = zonelist->zones; *z; z++) | |
173 | if (cpuset_zone_allowed(*z, gfp_mask)) | |
174 | node_clear((*z)->zone_pgdat->node_id, | |
175 | nodes); | |
176 | else | |
177 | return CONSTRAINT_CPUSET; | |
178 | ||
179 | if (!nodes_empty(nodes)) | |
180 | return CONSTRAINT_MEMORY_POLICY; | |
181 | #endif | |
182 | ||
183 | return CONSTRAINT_NONE; | |
184 | } | |
185 | ||
1da177e4 LT |
186 | /* |
187 | * Simple selection loop. We chose the process with the highest | |
188 | * number of 'points'. We expect the caller will lock the tasklist. | |
189 | * | |
190 | * (not docbooked, we don't want this one cluttering up the manual) | |
191 | */ | |
9827b781 | 192 | static struct task_struct *select_bad_process(unsigned long *ppoints) |
1da177e4 | 193 | { |
1da177e4 LT |
194 | struct task_struct *g, *p; |
195 | struct task_struct *chosen = NULL; | |
196 | struct timespec uptime; | |
9827b781 | 197 | *ppoints = 0; |
1da177e4 LT |
198 | |
199 | do_posix_clock_monotonic_gettime(&uptime); | |
a49335cc PJ |
200 | do_each_thread(g, p) { |
201 | unsigned long points; | |
202 | int releasing; | |
203 | ||
1da177e4 | 204 | /* skip the init task with pid == 1 */ |
a49335cc PJ |
205 | if (p->pid == 1) |
206 | continue; | |
207 | if (p->oomkilladj == OOM_DISABLE) | |
208 | continue; | |
ef08e3b4 | 209 | |
a49335cc | 210 | /* |
6937a25c | 211 | * This is in the process of releasing memory so wait for it |
a49335cc PJ |
212 | * to finish before killing some other task by mistake. |
213 | */ | |
214 | releasing = test_tsk_thread_flag(p, TIF_MEMDIE) || | |
215 | p->flags & PF_EXITING; | |
216 | if (releasing && !(p->flags & PF_DEAD)) | |
217 | return ERR_PTR(-1UL); | |
218 | if (p->flags & PF_SWAPOFF) | |
219 | return p; | |
220 | ||
221 | points = badness(p, uptime.tv_sec); | |
9827b781 | 222 | if (points > *ppoints || !chosen) { |
a49335cc | 223 | chosen = p; |
9827b781 | 224 | *ppoints = points; |
1da177e4 | 225 | } |
a49335cc | 226 | } while_each_thread(g, p); |
1da177e4 LT |
227 | return chosen; |
228 | } | |
229 | ||
230 | /** | |
231 | * We must be careful though to never send SIGKILL a process with | |
232 | * CAP_SYS_RAW_IO set, send SIGTERM instead (but it's unlikely that | |
233 | * we select a process with CAP_SYS_RAW_IO set). | |
234 | */ | |
36c8b586 | 235 | static void __oom_kill_task(struct task_struct *p, const char *message) |
1da177e4 LT |
236 | { |
237 | if (p->pid == 1) { | |
238 | WARN_ON(1); | |
239 | printk(KERN_WARNING "tried to kill init!\n"); | |
240 | return; | |
241 | } | |
242 | ||
243 | task_lock(p); | |
244 | if (!p->mm || p->mm == &init_mm) { | |
245 | WARN_ON(1); | |
246 | printk(KERN_WARNING "tried to kill an mm-less task!\n"); | |
247 | task_unlock(p); | |
248 | return; | |
249 | } | |
250 | task_unlock(p); | |
9b0f8b04 CL |
251 | printk(KERN_ERR "%s: Killed process %d (%s).\n", |
252 | message, p->pid, p->comm); | |
1da177e4 LT |
253 | |
254 | /* | |
255 | * We give our sacrificial lamb high priority and access to | |
256 | * all the memory it needs. That way it should be able to | |
257 | * exit() and clear out its resources quickly... | |
258 | */ | |
259 | p->time_slice = HZ; | |
260 | set_tsk_thread_flag(p, TIF_MEMDIE); | |
261 | ||
262 | force_sig(SIGKILL, p); | |
263 | } | |
264 | ||
36c8b586 | 265 | static int oom_kill_task(struct task_struct *p, const char *message) |
1da177e4 | 266 | { |
01315922 | 267 | struct mm_struct *mm; |
36c8b586 | 268 | struct task_struct *g, *q; |
1da177e4 | 269 | |
01315922 DP |
270 | mm = p->mm; |
271 | ||
272 | /* WARNING: mm may not be dereferenced since we did not obtain its | |
273 | * value from get_task_mm(p). This is OK since all we need to do is | |
274 | * compare mm to q->mm below. | |
275 | * | |
276 | * Furthermore, even if mm contains a non-NULL value, p->mm may | |
277 | * change to NULL at any time since we do not hold task_lock(p). | |
278 | * However, this is of no concern to us. | |
279 | */ | |
280 | ||
281 | if (mm == NULL || mm == &init_mm) | |
282 | return 1; | |
1da177e4 | 283 | |
9b0f8b04 | 284 | __oom_kill_task(p, message); |
1da177e4 LT |
285 | /* |
286 | * kill all processes that share the ->mm (i.e. all threads), | |
287 | * but are in a different thread group | |
288 | */ | |
289 | do_each_thread(g, q) | |
290 | if (q->mm == mm && q->tgid != p->tgid) | |
9b0f8b04 | 291 | __oom_kill_task(q, message); |
1da177e4 LT |
292 | while_each_thread(g, q); |
293 | ||
01315922 | 294 | return 0; |
1da177e4 LT |
295 | } |
296 | ||
01315922 DP |
297 | static int oom_kill_process(struct task_struct *p, unsigned long points, |
298 | const char *message) | |
1da177e4 | 299 | { |
1da177e4 LT |
300 | struct task_struct *c; |
301 | struct list_head *tsk; | |
302 | ||
9827b781 KG |
303 | printk(KERN_ERR "Out of Memory: Kill process %d (%s) score %li and " |
304 | "children.\n", p->pid, p->comm, points); | |
1da177e4 LT |
305 | /* Try to kill a child first */ |
306 | list_for_each(tsk, &p->children) { | |
307 | c = list_entry(tsk, struct task_struct, sibling); | |
308 | if (c->mm == p->mm) | |
309 | continue; | |
01315922 DP |
310 | if (!oom_kill_task(c, message)) |
311 | return 0; | |
1da177e4 | 312 | } |
9b0f8b04 | 313 | return oom_kill_task(p, message); |
1da177e4 LT |
314 | } |
315 | ||
8bc719d3 MS |
316 | static BLOCKING_NOTIFIER_HEAD(oom_notify_list); |
317 | ||
318 | int register_oom_notifier(struct notifier_block *nb) | |
319 | { | |
320 | return blocking_notifier_chain_register(&oom_notify_list, nb); | |
321 | } | |
322 | EXPORT_SYMBOL_GPL(register_oom_notifier); | |
323 | ||
324 | int unregister_oom_notifier(struct notifier_block *nb) | |
325 | { | |
326 | return blocking_notifier_chain_unregister(&oom_notify_list, nb); | |
327 | } | |
328 | EXPORT_SYMBOL_GPL(unregister_oom_notifier); | |
329 | ||
1da177e4 | 330 | /** |
6937a25c | 331 | * out_of_memory - kill the "best" process when we run out of memory |
1da177e4 LT |
332 | * |
333 | * If we run out of memory, we have the choice between either | |
334 | * killing a random task (bad), letting the system crash (worse) | |
335 | * OR try to be smart about which process to kill. Note that we | |
336 | * don't have to be perfect here, we just have to be good. | |
337 | */ | |
9b0f8b04 | 338 | void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order) |
1da177e4 | 339 | { |
36c8b586 | 340 | struct task_struct *p; |
d6713e04 | 341 | unsigned long points = 0; |
8bc719d3 MS |
342 | unsigned long freed = 0; |
343 | ||
344 | blocking_notifier_call_chain(&oom_notify_list, 0, &freed); | |
345 | if (freed > 0) | |
346 | /* Got some memory back in the last second. */ | |
347 | return; | |
1da177e4 | 348 | |
42639269 AB |
349 | if (printk_ratelimit()) { |
350 | printk("oom-killer: gfp_mask=0x%x, order=%d\n", | |
351 | gfp_mask, order); | |
b958f7d9 | 352 | dump_stack(); |
42639269 AB |
353 | show_mem(); |
354 | } | |
578c2fd6 | 355 | |
505970b9 | 356 | cpuset_lock(); |
1da177e4 | 357 | read_lock(&tasklist_lock); |
9b0f8b04 CL |
358 | |
359 | /* | |
360 | * Check if there were limitations on the allocation (only relevant for | |
361 | * NUMA) that may require different handling. | |
362 | */ | |
363 | switch (constrained_alloc(zonelist, gfp_mask)) { | |
364 | case CONSTRAINT_MEMORY_POLICY: | |
01315922 | 365 | oom_kill_process(current, points, |
9b0f8b04 CL |
366 | "No available memory (MPOL_BIND)"); |
367 | break; | |
368 | ||
369 | case CONSTRAINT_CPUSET: | |
01315922 | 370 | oom_kill_process(current, points, |
9b0f8b04 CL |
371 | "No available memory in cpuset"); |
372 | break; | |
373 | ||
374 | case CONSTRAINT_NONE: | |
fadd8fbd KH |
375 | if (sysctl_panic_on_oom) |
376 | panic("out of memory. panic_on_oom is selected\n"); | |
1da177e4 | 377 | retry: |
9b0f8b04 CL |
378 | /* |
379 | * Rambo mode: Shoot down a process and hope it solves whatever | |
380 | * issues we may have. | |
381 | */ | |
382 | p = select_bad_process(&points); | |
1da177e4 | 383 | |
9b0f8b04 CL |
384 | if (PTR_ERR(p) == -1UL) |
385 | goto out; | |
1da177e4 | 386 | |
9b0f8b04 CL |
387 | /* Found nothing?!?! Either we hang forever, or we panic. */ |
388 | if (!p) { | |
389 | read_unlock(&tasklist_lock); | |
390 | cpuset_unlock(); | |
391 | panic("Out of memory and no killable processes...\n"); | |
392 | } | |
1da177e4 | 393 | |
01315922 | 394 | if (oom_kill_process(p, points, "Out of memory")) |
9b0f8b04 CL |
395 | goto retry; |
396 | ||
397 | break; | |
398 | } | |
1da177e4 | 399 | |
9b0f8b04 | 400 | out: |
140ffcec | 401 | read_unlock(&tasklist_lock); |
505970b9 | 402 | cpuset_unlock(); |
1da177e4 LT |
403 | |
404 | /* | |
405 | * Give "p" a good chance of killing itself before we | |
2f659f46 | 406 | * retry to allocate memory unless "p" is current |
1da177e4 | 407 | */ |
2f659f46 | 408 | if (!test_thread_flag(TIF_MEMDIE)) |
140ffcec | 409 | schedule_timeout_uninterruptible(1); |
1da177e4 | 410 | } |