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...
8 * The routines in this file are used to kill a process when
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.
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.
18 #include <linux/oom.h>
20 #include <linux/err.h>
21 #include <linux/gfp.h>
22 #include <linux/sched.h>
23 #include <linux/swap.h>
24 #include <linux/timex.h>
25 #include <linux/jiffies.h>
26 #include <linux/cpuset.h>
27 #include <linux/module.h>
28 #include <linux/notifier.h>
29 #include <linux/memcontrol.h>
30 #include <linux/security.h>
32 int sysctl_panic_on_oom;
33 int sysctl_oom_kill_allocating_task;
34 int sysctl_oom_dump_tasks;
35 static DEFINE_SPINLOCK(zone_scan_lock);
39 * Is all threads of the target process nodes overlap ours?
41 static int has_intersects_mems_allowed(struct task_struct *tsk)
43 struct task_struct *t;
47 if (cpuset_mems_allowed_intersects(current, t))
55 static struct task_struct *find_lock_task_mm(struct task_struct *p)
57 struct task_struct *t = p;
64 } while_each_thread(p, t);
70 * badness - calculate a numeric value for how bad this task has been
71 * @p: task struct of which task we should calculate
72 * @uptime: current uptime in seconds
74 * The formula used is relatively simple and documented inline in the
75 * function. The main rationale is that we want to select a good task
76 * to kill when we run out of memory.
78 * Good in this context means that:
79 * 1) we lose the minimum amount of work done
80 * 2) we recover a large amount of memory
81 * 3) we don't kill anything innocent of eating tons of memory
82 * 4) we want to kill the minimum amount of processes (one)
83 * 5) we try to kill the process the user expects us to kill, this
84 * algorithm has been meticulously tuned to meet the principle
85 * of least surprise ... (be careful when you change it)
88 unsigned long badness(struct task_struct *p, unsigned long uptime)
90 unsigned long points, cpu_time, run_time;
91 struct task_struct *child;
92 struct task_struct *c, *t;
93 int oom_adj = p->signal->oom_adj;
94 struct task_cputime task_time;
98 if (oom_adj == OOM_DISABLE)
101 p = find_lock_task_mm(p);
106 * The memory size of the process is the basis for the badness.
108 points = p->mm->total_vm;
111 * After this unlock we can no longer dereference local variable `mm'
116 * swapoff can easily use up all memory, so kill those first.
118 if (p->flags & PF_OOM_ORIGIN)
122 * Processes which fork a lot of child processes are likely
123 * a good choice. We add half the vmsize of the children if they
124 * have an own mm. This prevents forking servers to flood the
125 * machine with an endless amount of children. In case a single
126 * child is eating the vast majority of memory, adding only half
127 * to the parents will make the child our kill candidate of choice.
131 list_for_each_entry(c, &t->children, sibling) {
132 child = find_lock_task_mm(c);
134 if (child->mm != p->mm)
135 points += child->mm->total_vm/2 + 1;
139 } while_each_thread(p, t);
142 * CPU time is in tens of seconds and run time is in thousands
143 * of seconds. There is no particular reason for this other than
144 * that it turned out to work very well in practice.
146 thread_group_cputime(p, &task_time);
147 utime = cputime_to_jiffies(task_time.utime);
148 stime = cputime_to_jiffies(task_time.stime);
149 cpu_time = (utime + stime) >> (SHIFT_HZ + 3);
152 if (uptime >= p->start_time.tv_sec)
153 run_time = (uptime - p->start_time.tv_sec) >> 10;
158 points /= int_sqrt(cpu_time);
160 points /= int_sqrt(int_sqrt(run_time));
163 * Niced processes are most likely less important, so double
164 * their badness points.
166 if (task_nice(p) > 0)
170 * Superuser processes are usually more important, so we make it
171 * less likely that we kill those.
173 if (has_capability_noaudit(p, CAP_SYS_ADMIN) ||
174 has_capability_noaudit(p, CAP_SYS_RESOURCE))
178 * We don't want to kill a process with direct hardware access.
179 * Not only could that mess up the hardware, but usually users
180 * tend to only have this flag set on applications they think
183 if (has_capability_noaudit(p, CAP_SYS_RAWIO))
187 * Adjust the score by oom_adj.
195 points >>= -(oom_adj);
199 printk(KERN_DEBUG "OOMkill: task %d (%s) got %lu points\n",
200 p->pid, p->comm, points);
206 * Determine the type of allocation constraint.
209 static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
210 gfp_t gfp_mask, nodemask_t *nodemask)
214 enum zone_type high_zoneidx = gfp_zone(gfp_mask);
217 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
218 * to kill current.We have to random task kill in this case.
219 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
221 if (gfp_mask & __GFP_THISNODE)
222 return CONSTRAINT_NONE;
225 * The nodemask here is a nodemask passed to alloc_pages(). Now,
226 * cpuset doesn't use this nodemask for its hardwall/softwall/hierarchy
227 * feature. mempolicy is an only user of nodemask here.
228 * check mempolicy's nodemask contains all N_HIGH_MEMORY
230 if (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask))
231 return CONSTRAINT_MEMORY_POLICY;
233 /* Check this allocation failure is caused by cpuset's wall function */
234 for_each_zone_zonelist_nodemask(zone, z, zonelist,
235 high_zoneidx, nodemask)
236 if (!cpuset_zone_allowed_softwall(zone, gfp_mask))
237 return CONSTRAINT_CPUSET;
239 return CONSTRAINT_NONE;
242 static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
243 gfp_t gfp_mask, nodemask_t *nodemask)
245 return CONSTRAINT_NONE;
250 * Simple selection loop. We chose the process with the highest
251 * number of 'points'. We expect the caller will lock the tasklist.
253 * (not docbooked, we don't want this one cluttering up the manual)
255 static struct task_struct *select_bad_process(unsigned long *ppoints,
256 struct mem_cgroup *mem)
258 struct task_struct *p;
259 struct task_struct *chosen = NULL;
260 struct timespec uptime;
263 do_posix_clock_monotonic_gettime(&uptime);
264 for_each_process(p) {
265 unsigned long points;
267 /* skip the init task and kthreads */
268 if (is_global_init(p) || (p->flags & PF_KTHREAD))
270 if (mem && !task_in_mem_cgroup(p, mem))
272 if (!has_intersects_mems_allowed(p))
276 * This task already has access to memory reserves and is
277 * being killed. Don't allow any other task access to the
280 * Note: this may have a chance of deadlock if it gets
281 * blocked waiting for another task which itself is waiting
282 * for memory. Is there a better alternative?
284 if (test_tsk_thread_flag(p, TIF_MEMDIE))
285 return ERR_PTR(-1UL);
288 * This is in the process of releasing memory so wait for it
289 * to finish before killing some other task by mistake.
291 * However, if p is the current task, we allow the 'kill' to
292 * go ahead if it is exiting: this will simply set TIF_MEMDIE,
293 * which will allow it to gain access to memory reserves in
294 * the process of exiting and releasing its resources.
295 * Otherwise we could get an easy OOM deadlock.
297 if ((p->flags & PF_EXITING) && p->mm) {
299 return ERR_PTR(-1UL);
302 *ppoints = ULONG_MAX;
305 if (p->signal->oom_adj == OOM_DISABLE)
308 points = badness(p, uptime.tv_sec);
309 if (points > *ppoints || !chosen) {
319 * dump_tasks - dump current memory state of all system tasks
320 * @mem: current's memory controller, if constrained
322 * Dumps the current memory state of all system tasks, excluding kernel threads.
323 * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj
326 * If the actual is non-NULL, only tasks that are a member of the mem_cgroup are
329 * Call with tasklist_lock read-locked.
331 static void dump_tasks(const struct mem_cgroup *mem)
333 struct task_struct *p;
334 struct task_struct *task;
336 printk(KERN_INFO "[ pid ] uid tgid total_vm rss cpu oom_adj "
338 for_each_process(p) {
339 if (p->flags & PF_KTHREAD)
341 if (mem && !task_in_mem_cgroup(p, mem))
344 task = find_lock_task_mm(p);
347 * This is a kthread or all of p's threads have already
348 * detached their mm's. There's no need to report
349 * them; they can't be oom killed anyway.
354 printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3u %3d %s\n",
355 task->pid, __task_cred(task)->uid, task->tgid,
356 task->mm->total_vm, get_mm_rss(task->mm),
357 task_cpu(task), task->signal->oom_adj, task->comm);
362 static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
363 struct mem_cgroup *mem)
365 pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
367 current->comm, gfp_mask, order, current->signal->oom_adj);
369 cpuset_print_task_mems_allowed(current);
370 task_unlock(current);
372 mem_cgroup_print_oom_info(mem, p);
374 if (sysctl_oom_dump_tasks)
378 #define K(x) ((x) << (PAGE_SHIFT-10))
381 * Send SIGKILL to the selected process irrespective of CAP_SYS_RAW_IO
382 * flag though it's unlikely that we select a process with CAP_SYS_RAW_IO
385 static void __oom_kill_task(struct task_struct *p, int verbose)
387 if (is_global_init(p)) {
389 printk(KERN_WARNING "tried to kill init!\n");
393 p = find_lock_task_mm(p);
398 printk(KERN_ERR "Killed process %d (%s) "
399 "vsz:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
400 task_pid_nr(p), p->comm,
402 K(get_mm_counter(p->mm, MM_ANONPAGES)),
403 K(get_mm_counter(p->mm, MM_FILEPAGES)));
407 * We give our sacrificial lamb high priority and access to
408 * all the memory it needs. That way it should be able to
409 * exit() and clear out its resources quickly...
411 p->rt.time_slice = HZ;
412 set_tsk_thread_flag(p, TIF_MEMDIE);
414 force_sig(SIGKILL, p);
417 static int oom_kill_task(struct task_struct *p)
419 /* WARNING: mm may not be dereferenced since we did not obtain its
420 * value from get_task_mm(p). This is OK since all we need to do is
421 * compare mm to q->mm below.
423 * Furthermore, even if mm contains a non-NULL value, p->mm may
424 * change to NULL at any time since we do not hold task_lock(p).
425 * However, this is of no concern to us.
427 if (!p->mm || p->signal->oom_adj == OOM_DISABLE)
430 __oom_kill_task(p, 1);
435 static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
436 unsigned long points, struct mem_cgroup *mem,
439 struct task_struct *c;
440 struct task_struct *t = p;
442 if (printk_ratelimit())
443 dump_header(p, gfp_mask, order, mem);
446 * If the task is already exiting, don't alarm the sysadmin or kill
447 * its children or threads, just set TIF_MEMDIE so it can die quickly
449 if (p->flags & PF_EXITING) {
450 set_tsk_thread_flag(p, TIF_MEMDIE);
454 printk(KERN_ERR "%s: kill process %d (%s) score %li or a child\n",
455 message, task_pid_nr(p), p->comm, points);
457 /* Try to kill a child first */
459 list_for_each_entry(c, &t->children, sibling) {
462 if (mem && !task_in_mem_cgroup(c, mem))
464 if (!oom_kill_task(c))
467 } while_each_thread(p, t);
469 return oom_kill_task(p);
472 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
473 void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
475 unsigned long points = 0;
476 struct task_struct *p;
478 if (sysctl_panic_on_oom == 2)
479 panic("out of memory(memcg). panic_on_oom is selected.\n");
480 read_lock(&tasklist_lock);
482 p = select_bad_process(&points, mem);
483 if (!p || PTR_ERR(p) == -1UL)
486 if (oom_kill_process(p, gfp_mask, 0, points, mem,
487 "Memory cgroup out of memory"))
490 read_unlock(&tasklist_lock);
494 static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
496 int register_oom_notifier(struct notifier_block *nb)
498 return blocking_notifier_chain_register(&oom_notify_list, nb);
500 EXPORT_SYMBOL_GPL(register_oom_notifier);
502 int unregister_oom_notifier(struct notifier_block *nb)
504 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
506 EXPORT_SYMBOL_GPL(unregister_oom_notifier);
509 * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero
510 * if a parallel OOM killing is already taking place that includes a zone in
511 * the zonelist. Otherwise, locks all zones in the zonelist and returns 1.
513 int try_set_zone_oom(struct zonelist *zonelist, gfp_t gfp_mask)
519 spin_lock(&zone_scan_lock);
520 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
521 if (zone_is_oom_locked(zone)) {
527 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
529 * Lock each zone in the zonelist under zone_scan_lock so a
530 * parallel invocation of try_set_zone_oom() doesn't succeed
533 zone_set_flag(zone, ZONE_OOM_LOCKED);
537 spin_unlock(&zone_scan_lock);
542 * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
543 * allocation attempts with zonelists containing them may now recall the OOM
544 * killer, if necessary.
546 void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
551 spin_lock(&zone_scan_lock);
552 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
553 zone_clear_flag(zone, ZONE_OOM_LOCKED);
555 spin_unlock(&zone_scan_lock);
559 * Must be called with tasklist_lock held for read.
561 static void __out_of_memory(gfp_t gfp_mask, int order)
563 struct task_struct *p;
564 unsigned long points;
566 if (sysctl_oom_kill_allocating_task)
567 if (!oom_kill_process(current, gfp_mask, order, 0, NULL,
568 "Out of memory (oom_kill_allocating_task)"))
572 * Rambo mode: Shoot down a process and hope it solves whatever
573 * issues we may have.
575 p = select_bad_process(&points, NULL);
577 if (PTR_ERR(p) == -1UL)
580 /* Found nothing?!?! Either we hang forever, or we panic. */
582 read_unlock(&tasklist_lock);
583 dump_header(NULL, gfp_mask, order, NULL);
584 panic("Out of memory and no killable processes...\n");
587 if (oom_kill_process(p, gfp_mask, order, points, NULL,
593 * pagefault handler calls into here because it is out of memory but
594 * doesn't know exactly how or why.
596 void pagefault_out_of_memory(void)
598 unsigned long freed = 0;
600 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
602 /* Got some memory back in the last second. */
605 if (sysctl_panic_on_oom)
606 panic("out of memory from page fault. panic_on_oom is selected.\n");
608 read_lock(&tasklist_lock);
609 __out_of_memory(0, 0); /* unknown gfp_mask and order */
610 read_unlock(&tasklist_lock);
613 * Give "p" a good chance of killing itself before we
614 * retry to allocate memory.
616 if (!test_thread_flag(TIF_MEMDIE))
617 schedule_timeout_uninterruptible(1);
621 * out_of_memory - kill the "best" process when we run out of memory
622 * @zonelist: zonelist pointer
623 * @gfp_mask: memory allocation flags
624 * @order: amount of memory being requested as a power of 2
626 * If we run out of memory, we have the choice between either
627 * killing a random task (bad), letting the system crash (worse)
628 * OR try to be smart about which process to kill. Note that we
629 * don't have to be perfect here, we just have to be good.
631 void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
632 int order, nodemask_t *nodemask)
634 unsigned long freed = 0;
635 enum oom_constraint constraint;
637 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
639 /* Got some memory back in the last second. */
643 * If current has a pending SIGKILL, then automatically select it. The
644 * goal is to allow it to allocate so that it may quickly exit and free
647 if (fatal_signal_pending(current)) {
648 set_thread_flag(TIF_MEMDIE);
652 if (sysctl_panic_on_oom == 2) {
653 dump_header(NULL, gfp_mask, order, NULL);
654 panic("out of memory. Compulsory panic_on_oom is selected.\n");
658 * Check if there were limitations on the allocation (only relevant for
659 * NUMA) that may require different handling.
661 constraint = constrained_alloc(zonelist, gfp_mask, nodemask);
662 read_lock(&tasklist_lock);
664 switch (constraint) {
665 case CONSTRAINT_MEMORY_POLICY:
666 oom_kill_process(current, gfp_mask, order, 0, NULL,
667 "No available memory (MPOL_BIND)");
670 case CONSTRAINT_NONE:
671 if (sysctl_panic_on_oom) {
672 dump_header(NULL, gfp_mask, order, NULL);
673 panic("out of memory. panic_on_oom is selected\n");
676 case CONSTRAINT_CPUSET:
677 __out_of_memory(gfp_mask, order);
681 read_unlock(&tasklist_lock);
684 * Give "p" a good chance of killing itself before we
685 * retry to allocate memory unless "p" is current
687 if (!test_thread_flag(TIF_MEMDIE))
688 schedule_timeout_uninterruptible(1);