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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 | ||
131 | /* | |
132 | * Adjust the score by oomkilladj. | |
133 | */ | |
134 | if (p->oomkilladj) { | |
135 | if (p->oomkilladj > 0) | |
136 | points <<= p->oomkilladj; | |
137 | else | |
138 | points >>= -(p->oomkilladj); | |
139 | } | |
140 | ||
141 | #ifdef DEBUG | |
142 | printk(KERN_DEBUG "OOMkill: task %d (%s) got %d points\n", | |
143 | p->pid, p->comm, points); | |
144 | #endif | |
145 | return points; | |
146 | } | |
147 | ||
9b0f8b04 CL |
148 | /* |
149 | * Types of limitations to the nodes from which allocations may occur | |
150 | */ | |
151 | #define CONSTRAINT_NONE 1 | |
152 | #define CONSTRAINT_MEMORY_POLICY 2 | |
153 | #define CONSTRAINT_CPUSET 3 | |
154 | ||
155 | /* | |
156 | * Determine the type of allocation constraint. | |
157 | */ | |
158 | static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask) | |
159 | { | |
160 | #ifdef CONFIG_NUMA | |
161 | struct zone **z; | |
162 | nodemask_t nodes = node_online_map; | |
163 | ||
164 | for (z = zonelist->zones; *z; z++) | |
165 | if (cpuset_zone_allowed(*z, gfp_mask)) | |
166 | node_clear((*z)->zone_pgdat->node_id, | |
167 | nodes); | |
168 | else | |
169 | return CONSTRAINT_CPUSET; | |
170 | ||
171 | if (!nodes_empty(nodes)) | |
172 | return CONSTRAINT_MEMORY_POLICY; | |
173 | #endif | |
174 | ||
175 | return CONSTRAINT_NONE; | |
176 | } | |
177 | ||
1da177e4 LT |
178 | /* |
179 | * Simple selection loop. We chose the process with the highest | |
180 | * number of 'points'. We expect the caller will lock the tasklist. | |
181 | * | |
182 | * (not docbooked, we don't want this one cluttering up the manual) | |
183 | */ | |
9827b781 | 184 | static struct task_struct *select_bad_process(unsigned long *ppoints) |
1da177e4 | 185 | { |
1da177e4 LT |
186 | struct task_struct *g, *p; |
187 | struct task_struct *chosen = NULL; | |
188 | struct timespec uptime; | |
9827b781 | 189 | *ppoints = 0; |
1da177e4 LT |
190 | |
191 | do_posix_clock_monotonic_gettime(&uptime); | |
a49335cc PJ |
192 | do_each_thread(g, p) { |
193 | unsigned long points; | |
194 | int releasing; | |
195 | ||
1da177e4 | 196 | /* skip the init task with pid == 1 */ |
a49335cc PJ |
197 | if (p->pid == 1) |
198 | continue; | |
199 | if (p->oomkilladj == OOM_DISABLE) | |
200 | continue; | |
ef08e3b4 PJ |
201 | /* If p's nodes don't overlap ours, it won't help to kill p. */ |
202 | if (!cpuset_excl_nodes_overlap(p)) | |
203 | continue; | |
204 | ||
a49335cc | 205 | /* |
6937a25c | 206 | * This is in the process of releasing memory so wait for it |
a49335cc PJ |
207 | * to finish before killing some other task by mistake. |
208 | */ | |
209 | releasing = test_tsk_thread_flag(p, TIF_MEMDIE) || | |
210 | p->flags & PF_EXITING; | |
211 | if (releasing && !(p->flags & PF_DEAD)) | |
212 | return ERR_PTR(-1UL); | |
213 | if (p->flags & PF_SWAPOFF) | |
214 | return p; | |
215 | ||
216 | points = badness(p, uptime.tv_sec); | |
9827b781 | 217 | if (points > *ppoints || !chosen) { |
a49335cc | 218 | chosen = p; |
9827b781 | 219 | *ppoints = points; |
1da177e4 | 220 | } |
a49335cc | 221 | } while_each_thread(g, p); |
1da177e4 LT |
222 | return chosen; |
223 | } | |
224 | ||
225 | /** | |
226 | * We must be careful though to never send SIGKILL a process with | |
227 | * CAP_SYS_RAW_IO set, send SIGTERM instead (but it's unlikely that | |
228 | * we select a process with CAP_SYS_RAW_IO set). | |
229 | */ | |
36c8b586 | 230 | static void __oom_kill_task(struct task_struct *p, const char *message) |
1da177e4 LT |
231 | { |
232 | if (p->pid == 1) { | |
233 | WARN_ON(1); | |
234 | printk(KERN_WARNING "tried to kill init!\n"); | |
235 | return; | |
236 | } | |
237 | ||
238 | task_lock(p); | |
239 | if (!p->mm || p->mm == &init_mm) { | |
240 | WARN_ON(1); | |
241 | printk(KERN_WARNING "tried to kill an mm-less task!\n"); | |
242 | task_unlock(p); | |
243 | return; | |
244 | } | |
245 | task_unlock(p); | |
9b0f8b04 CL |
246 | printk(KERN_ERR "%s: Killed process %d (%s).\n", |
247 | message, p->pid, p->comm); | |
1da177e4 LT |
248 | |
249 | /* | |
250 | * We give our sacrificial lamb high priority and access to | |
251 | * all the memory it needs. That way it should be able to | |
252 | * exit() and clear out its resources quickly... | |
253 | */ | |
254 | p->time_slice = HZ; | |
255 | set_tsk_thread_flag(p, TIF_MEMDIE); | |
256 | ||
257 | force_sig(SIGKILL, p); | |
258 | } | |
259 | ||
36c8b586 | 260 | static int oom_kill_task(struct task_struct *p, const char *message) |
1da177e4 | 261 | { |
01315922 | 262 | struct mm_struct *mm; |
36c8b586 | 263 | struct task_struct *g, *q; |
1da177e4 | 264 | |
01315922 DP |
265 | mm = p->mm; |
266 | ||
267 | /* WARNING: mm may not be dereferenced since we did not obtain its | |
268 | * value from get_task_mm(p). This is OK since all we need to do is | |
269 | * compare mm to q->mm below. | |
270 | * | |
271 | * Furthermore, even if mm contains a non-NULL value, p->mm may | |
272 | * change to NULL at any time since we do not hold task_lock(p). | |
273 | * However, this is of no concern to us. | |
274 | */ | |
275 | ||
276 | if (mm == NULL || mm == &init_mm) | |
277 | return 1; | |
1da177e4 | 278 | |
9b0f8b04 | 279 | __oom_kill_task(p, message); |
1da177e4 LT |
280 | /* |
281 | * kill all processes that share the ->mm (i.e. all threads), | |
282 | * but are in a different thread group | |
283 | */ | |
284 | do_each_thread(g, q) | |
285 | if (q->mm == mm && q->tgid != p->tgid) | |
9b0f8b04 | 286 | __oom_kill_task(q, message); |
1da177e4 LT |
287 | while_each_thread(g, q); |
288 | ||
01315922 | 289 | return 0; |
1da177e4 LT |
290 | } |
291 | ||
01315922 DP |
292 | static int oom_kill_process(struct task_struct *p, unsigned long points, |
293 | const char *message) | |
1da177e4 | 294 | { |
1da177e4 LT |
295 | struct task_struct *c; |
296 | struct list_head *tsk; | |
297 | ||
9827b781 KG |
298 | printk(KERN_ERR "Out of Memory: Kill process %d (%s) score %li and " |
299 | "children.\n", p->pid, p->comm, points); | |
1da177e4 LT |
300 | /* Try to kill a child first */ |
301 | list_for_each(tsk, &p->children) { | |
302 | c = list_entry(tsk, struct task_struct, sibling); | |
303 | if (c->mm == p->mm) | |
304 | continue; | |
01315922 DP |
305 | if (!oom_kill_task(c, message)) |
306 | return 0; | |
1da177e4 | 307 | } |
9b0f8b04 | 308 | return oom_kill_task(p, message); |
1da177e4 LT |
309 | } |
310 | ||
8bc719d3 MS |
311 | static BLOCKING_NOTIFIER_HEAD(oom_notify_list); |
312 | ||
313 | int register_oom_notifier(struct notifier_block *nb) | |
314 | { | |
315 | return blocking_notifier_chain_register(&oom_notify_list, nb); | |
316 | } | |
317 | EXPORT_SYMBOL_GPL(register_oom_notifier); | |
318 | ||
319 | int unregister_oom_notifier(struct notifier_block *nb) | |
320 | { | |
321 | return blocking_notifier_chain_unregister(&oom_notify_list, nb); | |
322 | } | |
323 | EXPORT_SYMBOL_GPL(unregister_oom_notifier); | |
324 | ||
1da177e4 | 325 | /** |
6937a25c | 326 | * out_of_memory - kill the "best" process when we run out of memory |
1da177e4 LT |
327 | * |
328 | * If we run out of memory, we have the choice between either | |
329 | * killing a random task (bad), letting the system crash (worse) | |
330 | * OR try to be smart about which process to kill. Note that we | |
331 | * don't have to be perfect here, we just have to be good. | |
332 | */ | |
9b0f8b04 | 333 | void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order) |
1da177e4 | 334 | { |
36c8b586 | 335 | struct task_struct *p; |
d6713e04 | 336 | unsigned long points = 0; |
8bc719d3 MS |
337 | unsigned long freed = 0; |
338 | ||
339 | blocking_notifier_call_chain(&oom_notify_list, 0, &freed); | |
340 | if (freed > 0) | |
341 | /* Got some memory back in the last second. */ | |
342 | return; | |
1da177e4 | 343 | |
42639269 AB |
344 | if (printk_ratelimit()) { |
345 | printk("oom-killer: gfp_mask=0x%x, order=%d\n", | |
346 | gfp_mask, order); | |
b958f7d9 | 347 | dump_stack(); |
42639269 AB |
348 | show_mem(); |
349 | } | |
578c2fd6 | 350 | |
505970b9 | 351 | cpuset_lock(); |
1da177e4 | 352 | read_lock(&tasklist_lock); |
9b0f8b04 CL |
353 | |
354 | /* | |
355 | * Check if there were limitations on the allocation (only relevant for | |
356 | * NUMA) that may require different handling. | |
357 | */ | |
358 | switch (constrained_alloc(zonelist, gfp_mask)) { | |
359 | case CONSTRAINT_MEMORY_POLICY: | |
01315922 | 360 | oom_kill_process(current, points, |
9b0f8b04 CL |
361 | "No available memory (MPOL_BIND)"); |
362 | break; | |
363 | ||
364 | case CONSTRAINT_CPUSET: | |
01315922 | 365 | oom_kill_process(current, points, |
9b0f8b04 CL |
366 | "No available memory in cpuset"); |
367 | break; | |
368 | ||
369 | case CONSTRAINT_NONE: | |
fadd8fbd KH |
370 | if (sysctl_panic_on_oom) |
371 | panic("out of memory. panic_on_oom is selected\n"); | |
1da177e4 | 372 | retry: |
9b0f8b04 CL |
373 | /* |
374 | * Rambo mode: Shoot down a process and hope it solves whatever | |
375 | * issues we may have. | |
376 | */ | |
377 | p = select_bad_process(&points); | |
1da177e4 | 378 | |
9b0f8b04 CL |
379 | if (PTR_ERR(p) == -1UL) |
380 | goto out; | |
1da177e4 | 381 | |
9b0f8b04 CL |
382 | /* Found nothing?!?! Either we hang forever, or we panic. */ |
383 | if (!p) { | |
384 | read_unlock(&tasklist_lock); | |
385 | cpuset_unlock(); | |
386 | panic("Out of memory and no killable processes...\n"); | |
387 | } | |
1da177e4 | 388 | |
01315922 | 389 | if (oom_kill_process(p, points, "Out of memory")) |
9b0f8b04 CL |
390 | goto retry; |
391 | ||
392 | break; | |
393 | } | |
1da177e4 | 394 | |
9b0f8b04 | 395 | out: |
140ffcec | 396 | read_unlock(&tasklist_lock); |
505970b9 | 397 | cpuset_unlock(); |
1da177e4 LT |
398 | |
399 | /* | |
400 | * Give "p" a good chance of killing itself before we | |
2f659f46 | 401 | * retry to allocate memory unless "p" is current |
1da177e4 | 402 | */ |
2f659f46 | 403 | if (!test_thread_flag(TIF_MEMDIE)) |
140ffcec | 404 | schedule_timeout_uninterruptible(1); |
1da177e4 | 405 | } |