lowmemorykiller.c revision a9c58b907dbc6821533dfc295b63caf111ff1f16 
1/* drivers/misc/lowmemorykiller.c
2 *
3 * The lowmemorykiller driver lets user-space specify a set of memory thresholds
4 * where processes with a range of oom_score_adj values will get killed. Specify
5 * the minimum oom_score_adj values in
6 * /sys/module/lowmemorykiller/parameters/adj and the number of free pages in
7 * /sys/module/lowmemorykiller/parameters/minfree. Both files take a comma
8 * separated list of numbers in ascending order.
9 *
10 * For example, write "0,8" to /sys/module/lowmemorykiller/parameters/adj and
11 * "1024,4096" to /sys/module/lowmemorykiller/parameters/minfree to kill
12 * processes with a oom_score_adj value of 8 or higher when the free memory
13 * drops below 4096 pages and kill processes with a oom_score_adj value of 0 or
14 * higher when the free memory drops below 1024 pages.
15 *
16 * The driver considers memory used for caches to be free, but if a large
17 * percentage of the cached memory is locked this can be very inaccurate
18 * and processes may not get killed until the normal oom killer is triggered.
19 *
20 * Copyright (C) 2007-2008 Google, Inc.
21 *
22 * This software is licensed under the terms of the GNU General Public
23 * License version 2, as published by the Free Software Foundation, and
24 * may be copied, distributed, and modified under those terms.
25 *
26 * This program is distributed in the hope that it will be useful,
27 * but WITHOUT ANY WARRANTY; without even the implied warranty of
28 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
29 * GNU General Public License for more details.
30 *
31 */
32
33#include <linux/module.h>
34#include <linux/kernel.h>
35#include <linux/mm.h>
36#include <linux/oom.h>
37#include <linux/sched.h>
38#include <linux/rcupdate.h>
39#include <linux/profile.h>
40#include <linux/notifier.h>
41
42static uint32_t lowmem_debug_level = 2;
43static short lowmem_adj[6] = {
44	0,
45	1,
46	6,
47	12,
48};
49static int lowmem_adj_size = 4;
50static int lowmem_minfree[6] = {
51	3 * 512,	/* 6MB */
52	2 * 1024,	/* 8MB */
53	4 * 1024,	/* 16MB */
54	16 * 1024,	/* 64MB */
55};
56static int lowmem_minfree_size = 4;
57
58static unsigned long lowmem_deathpending_timeout;
59
60#define lowmem_print(level, x...)			\
61	do {						\
62		if (lowmem_debug_level >= (level))	\
63			printk(x);			\
64	} while (0)
65
66static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
67{
68	struct task_struct *tsk;
69	struct task_struct *selected = NULL;
70	int rem = 0;
71	int tasksize;
72	int i;
73	short min_score_adj = OOM_SCORE_ADJ_MAX + 1;
74	int selected_tasksize = 0;
75	short selected_oom_score_adj;
76	int array_size = ARRAY_SIZE(lowmem_adj);
77	int other_free = global_page_state(NR_FREE_PAGES);
78	int other_file = global_page_state(NR_FILE_PAGES) -
79						global_page_state(NR_SHMEM);
80
81	if (lowmem_adj_size < array_size)
82		array_size = lowmem_adj_size;
83	if (lowmem_minfree_size < array_size)
84		array_size = lowmem_minfree_size;
85	for (i = 0; i < array_size; i++) {
86		if (other_free < lowmem_minfree[i] &&
87		    other_file < lowmem_minfree[i]) {
88			min_score_adj = lowmem_adj[i];
89			break;
90		}
91	}
92	if (sc->nr_to_scan > 0)
93		lowmem_print(3, "lowmem_shrink %lu, %x, ofree %d %d, ma %hd\n",
94				sc->nr_to_scan, sc->gfp_mask, other_free,
95				other_file, min_score_adj);
96	rem = global_page_state(NR_ACTIVE_ANON) +
97		global_page_state(NR_ACTIVE_FILE) +
98		global_page_state(NR_INACTIVE_ANON) +
99		global_page_state(NR_INACTIVE_FILE);
100	if (sc->nr_to_scan <= 0 || min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
101		lowmem_print(5, "lowmem_shrink %lu, %x, return %d\n",
102			     sc->nr_to_scan, sc->gfp_mask, rem);
103		return rem;
104	}
105	selected_oom_score_adj = min_score_adj;
106
107	rcu_read_lock();
108	for_each_process(tsk) {
109		struct task_struct *p;
110		short oom_score_adj;
111
112		if (tsk->flags & PF_KTHREAD)
113			continue;
114
115		p = find_lock_task_mm(tsk);
116		if (!p)
117			continue;
118
119		if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
120		    time_before_eq(jiffies, lowmem_deathpending_timeout)) {
121			task_unlock(p);
122			rcu_read_unlock();
123			return 0;
124		}
125		oom_score_adj = p->signal->oom_score_adj;
126		if (oom_score_adj < min_score_adj) {
127			task_unlock(p);
128			continue;
129		}
130		tasksize = get_mm_rss(p->mm);
131		task_unlock(p);
132		if (tasksize <= 0)
133			continue;
134		if (selected) {
135			if (oom_score_adj < selected_oom_score_adj)
136				continue;
137			if (oom_score_adj == selected_oom_score_adj &&
138			    tasksize <= selected_tasksize)
139				continue;
140		}
141		selected = p;
142		selected_tasksize = tasksize;
143		selected_oom_score_adj = oom_score_adj;
144		lowmem_print(2, "select %d (%s), adj %hd, size %d, to kill\n",
145			     p->pid, p->comm, oom_score_adj, tasksize);
146	}
147	if (selected) {
148		lowmem_print(1, "send sigkill to %d (%s), adj %hd, size %d\n",
149			     selected->pid, selected->comm,
150			     selected_oom_score_adj, selected_tasksize);
151		lowmem_deathpending_timeout = jiffies + HZ;
152		send_sig(SIGKILL, selected, 0);
153		set_tsk_thread_flag(selected, TIF_MEMDIE);
154		rem -= selected_tasksize;
155	}
156	lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
157		     sc->nr_to_scan, sc->gfp_mask, rem);
158	rcu_read_unlock();
159	return rem;
160}
161
162static struct shrinker lowmem_shrinker = {
163	.shrink = lowmem_shrink,
164	.seeks = DEFAULT_SEEKS * 16
165};
166
167static int __init lowmem_init(void)
168{
169	register_shrinker(&lowmem_shrinker);
170	return 0;
171}
172
173static void __exit lowmem_exit(void)
174{
175	unregister_shrinker(&lowmem_shrinker);
176}
177
178module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
179module_param_array_named(adj, lowmem_adj, short, &lowmem_adj_size,
180			 S_IRUGO | S_IWUSR);
181module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
182			 S_IRUGO | S_IWUSR);
183module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
184
185module_init(lowmem_init);
186module_exit(lowmem_exit);
187
188MODULE_LICENSE("GPL");
189
190