ia64/linux-2.6.18-xen.hg

view mm/oom_kill.c @ 452:c7ed6fe5dca0

kexec: dont initialise regions in reserve_memory()

There is no need to initialise efi_memmap_res and boot_param_res in
reserve_memory() for the initial xen domain as it is done in
machine_kexec_setup_resources() using values from the kexec hypercall.

Signed-off-by: Simon Horman <horms@verge.net.au>
author Keir Fraser <keir.fraser@citrix.com>
date Thu Feb 28 10:55:18 2008 +0000 (2008-02-28)
parents 831230e53067
children
line source
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 */
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>
25 int sysctl_panic_on_oom;
26 /* #define DEBUG */
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 */
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;
53 task_lock(p);
54 mm = p->mm;
55 if (!mm) {
56 task_unlock(p);
57 return 0;
58 }
60 /*
61 * The memory size of the process is the basis for the badness.
62 */
63 points = mm->total_vm;
65 /*
66 * After this unlock we can no longer dereference local variable `mm'
67 */
68 task_unlock(p);
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 }
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);
93 if (uptime >= p->start_time.tv_sec)
94 run_time = (uptime - p->start_time.tv_sec) >> 10;
95 else
96 run_time = 0;
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;
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;
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;
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;
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 }
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 }
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
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;
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;
169 if (!nodes_empty(nodes))
170 return CONSTRAINT_MEMORY_POLICY;
171 #endif
173 return CONSTRAINT_NONE;
174 }
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;
189 do_posix_clock_monotonic_gettime(&uptime);
190 do_each_thread(g, p) {
191 unsigned long points;
192 int releasing;
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;
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;
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 }
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(struct task_struct *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 }
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);
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);
255 force_sig(SIGKILL, p);
256 }
258 static int oom_kill_task(struct task_struct *p, const char *message)
259 {
260 struct mm_struct *mm;
261 struct task_struct *g, *q;
263 mm = p->mm;
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 */
274 if (mm == NULL || mm == &init_mm)
275 return 1;
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);
287 return 0;
288 }
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;
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 }
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 struct task_struct *p;
320 unsigned long points = 0;
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 }
329 cpuset_lock();
330 read_lock(&tasklist_lock);
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;
342 case CONSTRAINT_CPUSET:
343 oom_kill_process(current, points,
344 "No available memory in cpuset");
345 break;
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);
357 if (PTR_ERR(p) == -1UL)
358 goto out;
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 }
367 if (oom_kill_process(p, points, "Out of memory"))
368 goto retry;
370 break;
371 }
373 out:
374 read_unlock(&tasklist_lock);
375 cpuset_unlock();
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 }