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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
Paul Jacksona49335c2005-09-06 15:18:09 -07009 * 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.
Linus Torvalds1da177e2005-04-16 15:20:36 -070011 *
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>
Paul Jacksonef08e3b2005-09-06 15:18:13 -070023#include <linux/cpuset.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070024
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
Paul Jacksona49335c2005-09-06 15:18:09 -070030 * @uptime: current uptime in seconds
Linus Torvalds1da177e2005-04-16 15:20:36 -070031 *
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
46unsigned long badness(struct task_struct *p, unsigned long uptime)
47{
48 unsigned long points, cpu_time, run_time, s;
Andrew Morton97c2c9b2006-04-18 22:20:38 -070049 struct mm_struct *mm;
50 struct task_struct *child;
Linus Torvalds1da177e2005-04-16 15:20:36 -070051
Andrew Morton97c2c9b2006-04-18 22:20:38 -070052 task_lock(p);
53 mm = p->mm;
54 if (!mm) {
55 task_unlock(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -070056 return 0;
Andrew Morton97c2c9b2006-04-18 22:20:38 -070057 }
Linus Torvalds1da177e2005-04-16 15:20:36 -070058
59 /*
60 * The memory size of the process is the basis for the badness.
61 */
Andrew Morton97c2c9b2006-04-18 22:20:38 -070062 points = mm->total_vm;
63
64 /*
65 * After this unlock we can no longer dereference local variable `mm'
66 */
67 task_unlock(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -070068
69 /*
70 * Processes which fork a lot of child processes are likely
Kurt Garloff9827b782006-02-20 18:27:51 -080071 * a good choice. We add half the vmsize of the children if they
Linus Torvalds1da177e2005-04-16 15:20:36 -070072 * have an own mm. This prevents forking servers to flood the
Kurt Garloff9827b782006-02-20 18:27:51 -080073 * 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.
Linus Torvalds1da177e2005-04-16 15:20:36 -070076 */
Andrew Morton97c2c9b2006-04-18 22:20:38 -070077 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);
Linus Torvalds1da177e2005-04-16 15:20:36 -070082 }
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
145/*
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800146 * 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 */
155static 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
175/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176 * 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 */
Kurt Garloff9827b782006-02-20 18:27:51 -0800181static struct task_struct *select_bad_process(unsigned long *ppoints)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183 struct task_struct *g, *p;
184 struct task_struct *chosen = NULL;
185 struct timespec uptime;
Kurt Garloff9827b782006-02-20 18:27:51 -0800186 *ppoints = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700187
188 do_posix_clock_monotonic_gettime(&uptime);
Paul Jacksona49335c2005-09-06 15:18:09 -0700189 do_each_thread(g, p) {
190 unsigned long points;
191 int releasing;
192
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193 /* skip the init task with pid == 1 */
Paul Jacksona49335c2005-09-06 15:18:09 -0700194 if (p->pid == 1)
195 continue;
196 if (p->oomkilladj == OOM_DISABLE)
197 continue;
Paul Jacksonef08e3b2005-09-06 15:18:13 -0700198 /* 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
Paul Jacksona49335c2005-09-06 15:18:09 -0700202 /*
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;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212
Paul Jacksona49335c2005-09-06 15:18:09 -0700213 points = badness(p, uptime.tv_sec);
Kurt Garloff9827b782006-02-20 18:27:51 -0800214 if (points > *ppoints || !chosen) {
Paul Jacksona49335c2005-09-06 15:18:09 -0700215 chosen = p;
Kurt Garloff9827b782006-02-20 18:27:51 -0800216 *ppoints = points;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700217 }
Paul Jacksona49335c2005-09-06 15:18:09 -0700218 } while_each_thread(g, p);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219 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 */
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800227static void __oom_kill_task(task_t *p, const char *message)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700228{
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);
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800243 printk(KERN_ERR "%s: Killed process %d (%s).\n",
244 message, p->pid, p->comm);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700245
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
Dave Peterson01315922006-04-18 22:20:44 -0700257static int oom_kill_task(task_t *p, const char *message)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700258{
Dave Peterson01315922006-04-18 22:20:44 -0700259 struct mm_struct *mm;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700260 task_t * g, * q;
261
Dave Peterson01315922006-04-18 22:20:44 -0700262 mm = p->mm;
263
264 /* WARNING: mm may not be dereferenced since we did not obtain its
265 * value from get_task_mm(p). This is OK since all we need to do is
266 * compare mm to q->mm below.
267 *
268 * Furthermore, even if mm contains a non-NULL value, p->mm may
269 * change to NULL at any time since we do not hold task_lock(p).
270 * However, this is of no concern to us.
271 */
272
273 if (mm == NULL || mm == &init_mm)
274 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700275
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800276 __oom_kill_task(p, message);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700277 /*
278 * kill all processes that share the ->mm (i.e. all threads),
279 * but are in a different thread group
280 */
281 do_each_thread(g, q)
282 if (q->mm == mm && q->tgid != p->tgid)
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800283 __oom_kill_task(q, message);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700284 while_each_thread(g, q);
285
Dave Peterson01315922006-04-18 22:20:44 -0700286 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700287}
288
Dave Peterson01315922006-04-18 22:20:44 -0700289static int oom_kill_process(struct task_struct *p, unsigned long points,
290 const char *message)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700292 struct task_struct *c;
293 struct list_head *tsk;
294
Kurt Garloff9827b782006-02-20 18:27:51 -0800295 printk(KERN_ERR "Out of Memory: Kill process %d (%s) score %li and "
296 "children.\n", p->pid, p->comm, points);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700297 /* Try to kill a child first */
298 list_for_each(tsk, &p->children) {
299 c = list_entry(tsk, struct task_struct, sibling);
300 if (c->mm == p->mm)
301 continue;
Dave Peterson01315922006-04-18 22:20:44 -0700302 if (!oom_kill_task(c, message))
303 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700304 }
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800305 return oom_kill_task(p, message);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700306}
307
308/**
309 * oom_kill - kill the "best" process when we run out of memory
310 *
311 * If we run out of memory, we have the choice between either
312 * killing a random task (bad), letting the system crash (worse)
313 * OR try to be smart about which process to kill. Note that we
314 * don't have to be perfect here, we just have to be good.
315 */
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800316void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700317{
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800318 task_t *p;
Andrew Mortond6713e02006-02-28 16:59:19 -0800319 unsigned long points = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320
Anton Blanchard42639262005-07-07 17:56:06 -0700321 if (printk_ratelimit()) {
322 printk("oom-killer: gfp_mask=0x%x, order=%d\n",
323 gfp_mask, order);
Andrew Mortonb958f7d2006-02-01 03:05:51 -0800324 dump_stack();
Anton Blanchard42639262005-07-07 17:56:06 -0700325 show_mem();
326 }
Janet Morgan578c2fd2005-06-21 17:14:56 -0700327
Paul Jackson505970b2006-01-14 13:21:06 -0800328 cpuset_lock();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700329 read_lock(&tasklist_lock);
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800330
331 /*
332 * Check if there were limitations on the allocation (only relevant for
333 * NUMA) that may require different handling.
334 */
335 switch (constrained_alloc(zonelist, gfp_mask)) {
336 case CONSTRAINT_MEMORY_POLICY:
Dave Peterson01315922006-04-18 22:20:44 -0700337 oom_kill_process(current, points,
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800338 "No available memory (MPOL_BIND)");
339 break;
340
341 case CONSTRAINT_CPUSET:
Dave Peterson01315922006-04-18 22:20:44 -0700342 oom_kill_process(current, points,
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800343 "No available memory in cpuset");
344 break;
345
346 case CONSTRAINT_NONE:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347retry:
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800348 /*
349 * Rambo mode: Shoot down a process and hope it solves whatever
350 * issues we may have.
351 */
352 p = select_bad_process(&points);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700353
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800354 if (PTR_ERR(p) == -1UL)
355 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700356
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800357 /* Found nothing?!?! Either we hang forever, or we panic. */
358 if (!p) {
359 read_unlock(&tasklist_lock);
360 cpuset_unlock();
361 panic("Out of memory and no killable processes...\n");
362 }
363
Dave Peterson01315922006-04-18 22:20:44 -0700364 if (oom_kill_process(p, points, "Out of memory"))
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800365 goto retry;
366
367 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368 }
369
Christoph Lameter9b0f8b02006-02-20 18:27:52 -0800370out:
Andrew Morton140ffce2006-03-02 02:54:28 -0800371 read_unlock(&tasklist_lock);
Paul Jackson505970b2006-01-14 13:21:06 -0800372 cpuset_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700373
374 /*
375 * Give "p" a good chance of killing itself before we
Kirill Korotaev2f659f42006-01-08 01:01:05 -0800376 * retry to allocate memory unless "p" is current
Linus Torvalds1da177e2005-04-16 15:20:36 -0700377 */
Kirill Korotaev2f659f42006-01-08 01:01:05 -0800378 if (!test_thread_flag(TIF_MEMDIE))
Andrew Morton140ffce2006-03-02 02:54:28 -0800379 schedule_timeout_uninterruptible(1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700380}