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