kernel26-2.6.12-alx-r9/mm/oom_kill.c

/*
 *  linux/mm/oom_kill.c
 * 
 *  Copyright (C)  1998,2000  Rik van Riel
 *	Thanks go out to Claus Fischer for some serious inspiration and
 *	for goading me into coding this file...
 *
 *  The routines in this file are used to kill a process when
 *  we're seriously out of memory. This gets called from kswapd()
 *  in linux/mm/vmscan.c when we really run out of memory.
 *
 *  Since we won't call these routines often (on a well-configured
 *  machine) this file will double as a 'coding guide' and a signpost
 *  for newbie kernel hackers. It features several pointers to major
 *  kernel subsystems and hints as to where to find out what things do.
 */

#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/swap.h>
#include <linux/timex.h>
#include <linux/jiffies.h>

/* #define DEBUG */

/**
 * oom_badness - calculate a numeric value for how bad this task has been
 * @p: task struct of which task we should calculate
 * @p: current uptime in seconds
 *
 * The formula used is relatively simple and documented inline in the
 * function. The main rationale is that we want to select a good task
 * to kill when we run out of memory.
 *
 * Good in this context means that:
 * 1) we lose the minimum amount of work done
 * 2) we recover a large amount of memory
 * 3) we don't kill anything innocent of eating tons of memory
 * 4) we want to kill the minimum amount of processes (one)
 * 5) we try to kill the process the user expects us to kill, this
 *    algorithm has been meticulously tuned to meet the principle
 *    of least surprise ... (be careful when you change it)
 */

unsigned long badness(struct task_struct *p, unsigned long uptime)
{
	unsigned long points, cpu_time, run_time, s;
	struct list_head *tsk;

	if (!p->mm)
		return 0;

	/*
	 * The memory size of the process is the basis for the badness.
	 */
	points = p->mm->total_vm;

	/*
	 * Processes which fork a lot of child processes are likely
	 * a good choice. We add the vmsize of the childs if they
	 * have an own mm. This prevents forking servers to flood the
	 * machine with an endless amount of childs
	 */
	list_for_each(tsk, &p->children) {
		struct task_struct *chld;
		chld = list_entry(tsk, struct task_struct, sibling);
		if (chld->mm != p->mm && chld->mm)
			points += chld->mm->total_vm;
	}

	/*
	 * CPU time is in tens of seconds and run time is in thousands
         * of seconds. There is no particular reason for this other than
         * that it turned out to work very well in practice.
	 */
	cpu_time = (cputime_to_jiffies(p->utime) + cputime_to_jiffies(p->stime))
		>> (SHIFT_HZ + 3);

	if (uptime >= p->start_time.tv_sec)
		run_time = (uptime - p->start_time.tv_sec) >> 10;
	else
		run_time = 0;

	s = int_sqrt(cpu_time);
	if (s)
		points /= s;
	s = int_sqrt(int_sqrt(run_time));
	if (s)
		points /= s;

	/*
	 * Niced processes are most likely less important, so double
	 * their badness points.
	 */
	if (task_nice(p) > 0)
		points *= 2;

	/*
	 * Superuser processes are usually more important, so we make it
	 * less likely that we kill those.
	 */
	if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_ADMIN) ||
				p->uid == 0 || p->euid == 0)
		points /= 4;

	/*
	 * We don't want to kill a process with direct hardware access.
	 * Not only could that mess up the hardware, but usually users
	 * tend to only have this flag set on applications they think
	 * of as important.
	 */
	if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_RAWIO))
		points /= 4;

	/*
	 * Adjust the score by oomkilladj.
	 */
	if (p->oomkilladj) {
		if (p->oomkilladj > 0)
			points <<= p->oomkilladj;
		else
			points >>= -(p->oomkilladj);
	}

#ifdef DEBUG
	printk(KERN_DEBUG "OOMkill: task %d (%s) got %d points\n",
	p->pid, p->comm, points);
#endif
	return points;
}

/*
 * Simple selection loop. We chose the process with the highest
 * number of 'points'. We expect the caller will lock the tasklist.
 *
 * (not docbooked, we don't want this one cluttering up the manual)
 */
static struct task_struct * select_bad_process(void)
{
	unsigned long maxpoints = 0;
	struct task_struct *g, *p;
	struct task_struct *chosen = NULL;
	struct timespec uptime;

	do_posix_clock_monotonic_gettime(&uptime);
	do_each_thread(g, p)
		/* skip the init task with pid == 1 */
		if (p->pid > 1 && p->oomkilladj != OOM_DISABLE) {
			unsigned long points;

			/*
			 * This is in the process of releasing memory so wait it
			 * to finish before killing some other task by mistake.
			 */
			if ((unlikely(test_tsk_thread_flag(p, TIF_MEMDIE)) || (p->flags & PF_EXITING)) &&
			    !(p->flags & PF_DEAD))
				return ERR_PTR(-1UL);
			if (p->flags & PF_SWAPOFF)
				return p;

			points = badness(p, uptime.tv_sec);
			if (points > maxpoints || !chosen) {
				chosen = p;
				maxpoints = points;
			}
		}
	while_each_thread(g, p);
	return chosen;
}

/**
 * We must be careful though to never send SIGKILL a process with
 * CAP_SYS_RAW_IO set, send SIGTERM instead (but it's unlikely that
 * we select a process with CAP_SYS_RAW_IO set).
 */
static void __oom_kill_task(task_t *p)
{
	if (p->pid == 1) {
		WARN_ON(1);
		printk(KERN_WARNING "tried to kill init!\n");
		return;
	}

	task_lock(p);
	if (!p->mm || p->mm == &init_mm) {
		WARN_ON(1);
		printk(KERN_WARNING "tried to kill an mm-less task!\n");
		task_unlock(p);
		return;
	}
	task_unlock(p);
	printk(KERN_ERR "Out of Memory: Killed process %d (%s).\n", p->pid, p->comm);

	/*
	 * We give our sacrificial lamb high priority and access to
	 * all the memory it needs. That way it should be able to
	 * exit() and clear out its resources quickly...
	 */
	p->time_slice = HZ;
	set_tsk_thread_flag(p, TIF_MEMDIE);

	force_sig(SIGKILL, p);
}

static struct mm_struct *oom_kill_task(task_t *p)
{
	struct mm_struct *mm = get_task_mm(p);
	task_t * g, * q;

	if (!mm)
		return NULL;
	if (mm == &init_mm) {
		mmput(mm);
		return NULL;
	}

	__oom_kill_task(p);
	/*
	 * kill all processes that share the ->mm (i.e. all threads),
	 * but are in a different thread group
	 */
	do_each_thread(g, q)
		if (q->mm == mm && q->tgid != p->tgid)
			__oom_kill_task(q);
	while_each_thread(g, q);

	return mm;
}

static struct mm_struct *oom_kill_process(struct task_struct *p)
{
 	struct mm_struct *mm;
	struct task_struct *c;
	struct list_head *tsk;

	/* Try to kill a child first */
	list_for_each(tsk, &p->children) {
		c = list_entry(tsk, struct task_struct, sibling);
		if (c->mm == p->mm)
			continue;
		mm = oom_kill_task(c);
		if (mm)
			return mm;
	}
	return oom_kill_task(p);
}

/**
 * oom_kill - kill the "best" process when we run out of memory
 *
 * If we run out of memory, we have the choice between either
 * killing a random task (bad), letting the system crash (worse)
 * OR try to be smart about which process to kill. Note that we
 * don't have to be perfect here, we just have to be good.
 */
void out_of_memory(unsigned int __nocast gfp_mask)
{
	struct mm_struct *mm = NULL;
	task_t * p;

	read_lock(&tasklist_lock);
retry:
	p = select_bad_process();

	if (PTR_ERR(p) == -1UL)
		goto out;

	/* Found nothing?!?! Either we hang forever, or we panic. */
	if (!p) {
		read_unlock(&tasklist_lock);
		show_free_areas();
		panic("Out of memory and no killable processes...\n");
	}

	printk("oom-killer: gfp_mask=0x%x\n", gfp_mask);
	show_free_areas();
	mm = oom_kill_process(p);
	if (!mm)
		goto retry;

 out:
	read_unlock(&tasklist_lock);
	if (mm)
		mmput(mm);

	/*
	 * Give "p" a good chance of killing itself before we
	 * retry to allocate memory.
	 */
	__set_current_state(TASK_INTERRUPTIBLE);
	schedule_timeout(1);
}
1	niro	628	/*
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			}