Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/mm/oom_kill.c
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
File MIME type: text/plain
File size: 7547 byte(s)
Tag kernel26-2.6.12-alx-r9
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 kswapd() |
10 | * in linux/mm/vmscan.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 | |
24 | /* #define DEBUG */ |
25 | |
26 | /** |
27 | * oom_badness - calculate a numeric value for how bad this task has been |
28 | * @p: task struct of which task we should calculate |
29 | * @p: current uptime in seconds |
30 | * |
31 | * The formula used is relatively simple and documented inline in the |
32 | * function. The main rationale is that we want to select a good task |
33 | * to kill when we run out of memory. |
34 | * |
35 | * Good in this context means that: |
36 | * 1) we lose the minimum amount of work done |
37 | * 2) we recover a large amount of memory |
38 | * 3) we don't kill anything innocent of eating tons of memory |
39 | * 4) we want to kill the minimum amount of processes (one) |
40 | * 5) we try to kill the process the user expects us to kill, this |
41 | * algorithm has been meticulously tuned to meet the principle |
42 | * of least surprise ... (be careful when you change it) |
43 | */ |
44 | |
45 | unsigned long badness(struct task_struct *p, unsigned long uptime) |
46 | { |
47 | unsigned long points, cpu_time, run_time, s; |
48 | struct list_head *tsk; |
49 | |
50 | if (!p->mm) |
51 | return 0; |
52 | |
53 | /* |
54 | * The memory size of the process is the basis for the badness. |
55 | */ |
56 | points = p->mm->total_vm; |
57 | |
58 | /* |
59 | * Processes which fork a lot of child processes are likely |
60 | * a good choice. We add the vmsize of the childs if they |
61 | * have an own mm. This prevents forking servers to flood the |
62 | * machine with an endless amount of childs |
63 | */ |
64 | list_for_each(tsk, &p->children) { |
65 | struct task_struct *chld; |
66 | chld = list_entry(tsk, struct task_struct, sibling); |
67 | if (chld->mm != p->mm && chld->mm) |
68 | points += chld->mm->total_vm; |
69 | } |
70 | |
71 | /* |
72 | * CPU time is in tens of seconds and run time is in thousands |
73 | * of seconds. There is no particular reason for this other than |
74 | * that it turned out to work very well in practice. |
75 | */ |
76 | cpu_time = (cputime_to_jiffies(p->utime) + cputime_to_jiffies(p->stime)) |
77 | >> (SHIFT_HZ + 3); |
78 | |
79 | if (uptime >= p->start_time.tv_sec) |
80 | run_time = (uptime - p->start_time.tv_sec) >> 10; |
81 | else |
82 | run_time = 0; |
83 | |
84 | s = int_sqrt(cpu_time); |
85 | if (s) |
86 | points /= s; |
87 | s = int_sqrt(int_sqrt(run_time)); |
88 | if (s) |
89 | points /= s; |
90 | |
91 | /* |
92 | * Niced processes are most likely less important, so double |
93 | * their badness points. |
94 | */ |
95 | if (task_nice(p) > 0) |
96 | points *= 2; |
97 | |
98 | /* |
99 | * Superuser processes are usually more important, so we make it |
100 | * less likely that we kill those. |
101 | */ |
102 | if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_ADMIN) || |
103 | p->uid == 0 || p->euid == 0) |
104 | points /= 4; |
105 | |
106 | /* |
107 | * We don't want to kill a process with direct hardware access. |
108 | * Not only could that mess up the hardware, but usually users |
109 | * tend to only have this flag set on applications they think |
110 | * of as important. |
111 | */ |
112 | if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_RAWIO)) |
113 | points /= 4; |
114 | |
115 | /* |
116 | * Adjust the score by oomkilladj. |
117 | */ |
118 | if (p->oomkilladj) { |
119 | if (p->oomkilladj > 0) |
120 | points <<= p->oomkilladj; |
121 | else |
122 | points >>= -(p->oomkilladj); |
123 | } |
124 | |
125 | #ifdef DEBUG |
126 | printk(KERN_DEBUG "OOMkill: task %d (%s) got %d points\n", |
127 | p->pid, p->comm, points); |
128 | #endif |
129 | return points; |
130 | } |
131 | |
132 | /* |
133 | * Simple selection loop. We chose the process with the highest |
134 | * number of 'points'. We expect the caller will lock the tasklist. |
135 | * |
136 | * (not docbooked, we don't want this one cluttering up the manual) |
137 | */ |
138 | static struct task_struct * select_bad_process(void) |
139 | { |
140 | unsigned long maxpoints = 0; |
141 | struct task_struct *g, *p; |
142 | struct task_struct *chosen = NULL; |
143 | struct timespec uptime; |
144 | |
145 | do_posix_clock_monotonic_gettime(&uptime); |
146 | do_each_thread(g, p) |
147 | /* skip the init task with pid == 1 */ |
148 | if (p->pid > 1 && p->oomkilladj != OOM_DISABLE) { |
149 | unsigned long points; |
150 | |
151 | /* |
152 | * This is in the process of releasing memory so wait it |
153 | * to finish before killing some other task by mistake. |
154 | */ |
155 | if ((unlikely(test_tsk_thread_flag(p, TIF_MEMDIE)) || (p->flags & PF_EXITING)) && |
156 | !(p->flags & PF_DEAD)) |
157 | return ERR_PTR(-1UL); |
158 | if (p->flags & PF_SWAPOFF) |
159 | return p; |
160 | |
161 | points = badness(p, uptime.tv_sec); |
162 | if (points > maxpoints || !chosen) { |
163 | chosen = p; |
164 | maxpoints = points; |
165 | } |
166 | } |
167 | while_each_thread(g, p); |
168 | return chosen; |
169 | } |
170 | |
171 | /** |
172 | * We must be careful though to never send SIGKILL a process with |
173 | * CAP_SYS_RAW_IO set, send SIGTERM instead (but it's unlikely that |
174 | * we select a process with CAP_SYS_RAW_IO set). |
175 | */ |
176 | static void __oom_kill_task(task_t *p) |
177 | { |
178 | if (p->pid == 1) { |
179 | WARN_ON(1); |
180 | printk(KERN_WARNING "tried to kill init!\n"); |
181 | return; |
182 | } |
183 | |
184 | task_lock(p); |
185 | if (!p->mm || p->mm == &init_mm) { |
186 | WARN_ON(1); |
187 | printk(KERN_WARNING "tried to kill an mm-less task!\n"); |
188 | task_unlock(p); |
189 | return; |
190 | } |
191 | task_unlock(p); |
192 | printk(KERN_ERR "Out of Memory: Killed process %d (%s).\n", p->pid, p->comm); |
193 | |
194 | /* |
195 | * We give our sacrificial lamb high priority and access to |
196 | * all the memory it needs. That way it should be able to |
197 | * exit() and clear out its resources quickly... |
198 | */ |
199 | p->time_slice = HZ; |
200 | set_tsk_thread_flag(p, TIF_MEMDIE); |
201 | |
202 | force_sig(SIGKILL, p); |
203 | } |
204 | |
205 | static struct mm_struct *oom_kill_task(task_t *p) |
206 | { |
207 | struct mm_struct *mm = get_task_mm(p); |
208 | task_t * g, * q; |
209 | |
210 | if (!mm) |
211 | return NULL; |
212 | if (mm == &init_mm) { |
213 | mmput(mm); |
214 | return NULL; |
215 | } |
216 | |
217 | __oom_kill_task(p); |
218 | /* |
219 | * kill all processes that share the ->mm (i.e. all threads), |
220 | * but are in a different thread group |
221 | */ |
222 | do_each_thread(g, q) |
223 | if (q->mm == mm && q->tgid != p->tgid) |
224 | __oom_kill_task(q); |
225 | while_each_thread(g, q); |
226 | |
227 | return mm; |
228 | } |
229 | |
230 | static struct mm_struct *oom_kill_process(struct task_struct *p) |
231 | { |
232 | struct mm_struct *mm; |
233 | struct task_struct *c; |
234 | struct list_head *tsk; |
235 | |
236 | /* Try to kill a child first */ |
237 | list_for_each(tsk, &p->children) { |
238 | c = list_entry(tsk, struct task_struct, sibling); |
239 | if (c->mm == p->mm) |
240 | continue; |
241 | mm = oom_kill_task(c); |
242 | if (mm) |
243 | return mm; |
244 | } |
245 | return oom_kill_task(p); |
246 | } |
247 | |
248 | /** |
249 | * oom_kill - kill the "best" process when we run out of memory |
250 | * |
251 | * If we run out of memory, we have the choice between either |
252 | * killing a random task (bad), letting the system crash (worse) |
253 | * OR try to be smart about which process to kill. Note that we |
254 | * don't have to be perfect here, we just have to be good. |
255 | */ |
256 | void out_of_memory(unsigned int __nocast gfp_mask) |
257 | { |
258 | struct mm_struct *mm = NULL; |
259 | task_t * p; |
260 | |
261 | read_lock(&tasklist_lock); |
262 | retry: |
263 | p = select_bad_process(); |
264 | |
265 | if (PTR_ERR(p) == -1UL) |
266 | goto out; |
267 | |
268 | /* Found nothing?!?! Either we hang forever, or we panic. */ |
269 | if (!p) { |
270 | read_unlock(&tasklist_lock); |
271 | show_free_areas(); |
272 | panic("Out of memory and no killable processes...\n"); |
273 | } |
274 | |
275 | printk("oom-killer: gfp_mask=0x%x\n", gfp_mask); |
276 | show_free_areas(); |
277 | mm = oom_kill_process(p); |
278 | if (!mm) |
279 | goto retry; |
280 | |
281 | out: |
282 | read_unlock(&tasklist_lock); |
283 | if (mm) |
284 | mmput(mm); |
285 | |
286 | /* |
287 | * Give "p" a good chance of killing itself before we |
288 | * retry to allocate memory. |
289 | */ |
290 | __set_current_state(TASK_INTERRUPTIBLE); |
291 | schedule_timeout(1); |
292 | } |