[mirror_ubuntu-zesty-kernel.git] / 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) {
			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);
}
Commit	Line	Data
1da177e4 LT	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) {
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	}