mm/oom_kill.c - third_party/linux - Git at Google

 /*
  *  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);
 }
	/*
	* 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);
	}