lowmemorykiller.c revision 99150f6a1a015de275a83ca95aa5f4054b409f40 
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/swap.h>
39#include <linux/rcupdate.h>
40#include <linux/profile.h>
41#include <linux/notifier.h>
42
43static uint32_t lowmem_debug_level = 1;
44static short lowmem_adj[6] = {
45	0,
46	1,
47	6,
48	12,
49};
50static int lowmem_adj_size = 4;
51static int lowmem_minfree[6] = {
52	3 * 512,	/* 6MB */
53	2 * 1024,	/* 8MB */
54	4 * 1024,	/* 16MB */
55	16 * 1024,	/* 64MB */
56};
57static int lowmem_minfree_size = 4;
58
59static unsigned long lowmem_deathpending_timeout;
60
61#define lowmem_print(level, x...)			\
62	do {						\
63		if (lowmem_debug_level >= (level))	\
64			printk(x);			\
65	} while (0)
66
67static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
68{
69	struct task_struct *tsk;
70	struct task_struct *selected = NULL;
71	int rem = 0;
72	int tasksize;
73	int i;
74	short min_score_adj = OOM_SCORE_ADJ_MAX + 1;
75	int selected_tasksize = 0;
76	short selected_oom_score_adj;
77	int array_size = ARRAY_SIZE(lowmem_adj);
78	int other_free = global_page_state(NR_FREE_PAGES) - totalreserve_pages;
79	int other_file = global_page_state(NR_FILE_PAGES) -
80						global_page_state(NR_SHMEM);
81
82	if (lowmem_adj_size < array_size)
83		array_size = lowmem_adj_size;
84	if (lowmem_minfree_size < array_size)
85		array_size = lowmem_minfree_size;
86	for (i = 0; i < array_size; i++) {
87		if (other_free < lowmem_minfree[i] &&
88		    other_file < lowmem_minfree[i]) {
89			min_score_adj = lowmem_adj[i];
90			break;
91		}
92	}
93	if (sc->nr_to_scan > 0)
94		lowmem_print(3, "lowmem_shrink %lu, %x, ofree %d %d, ma %hd\n",
95				sc->nr_to_scan, sc->gfp_mask, other_free,
96				other_file, min_score_adj);
97	rem = global_page_state(NR_ACTIVE_ANON) +
98		global_page_state(NR_ACTIVE_FILE) +
99		global_page_state(NR_INACTIVE_ANON) +
100		global_page_state(NR_INACTIVE_FILE);
101	if (sc->nr_to_scan <= 0 || min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
102		lowmem_print(5, "lowmem_shrink %lu, %x, return %d\n",
103			     sc->nr_to_scan, sc->gfp_mask, rem);
104		return rem;
105	}
106	selected_oom_score_adj = min_score_adj;
107
108	rcu_read_lock();
109	for_each_process(tsk) {
110		struct task_struct *p;
111		short oom_score_adj;
112
113		if (tsk->flags & PF_KTHREAD)
114			continue;
115
116		p = find_lock_task_mm(tsk);
117		if (!p)
118			continue;
119
120		if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
121		    time_before_eq(jiffies, lowmem_deathpending_timeout)) {
122			task_unlock(p);
123			rcu_read_unlock();
124			return 0;
125		}
126		oom_score_adj = p->signal->oom_score_adj;
127		if (oom_score_adj < min_score_adj) {
128			task_unlock(p);
129			continue;
130		}
131		tasksize = get_mm_rss(p->mm);
132		task_unlock(p);
133		if (tasksize <= 0)
134			continue;
135		if (selected) {
136			if (oom_score_adj < selected_oom_score_adj)
137				continue;
138			if (oom_score_adj == selected_oom_score_adj &&
139			    tasksize <= selected_tasksize)
140				continue;
141		}
142		selected = p;
143		selected_tasksize = tasksize;
144		selected_oom_score_adj = oom_score_adj;
145		lowmem_print(2, "select %d (%s), adj %hd, size %d, to kill\n",
146			     p->pid, p->comm, oom_score_adj, tasksize);
147	}
148	if (selected) {
149		lowmem_print(1, "send sigkill to %d (%s), adj %hd, size %d\n",
150			     selected->pid, selected->comm,
151			     selected_oom_score_adj, selected_tasksize);
152		lowmem_deathpending_timeout = jiffies + HZ;
153		send_sig(SIGKILL, selected, 0);
154		set_tsk_thread_flag(selected, TIF_MEMDIE);
155		rem -= selected_tasksize;
156	}
157	lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
158		     sc->nr_to_scan, sc->gfp_mask, rem);
159	rcu_read_unlock();
160	return rem;
161}
162
163static struct shrinker lowmem_shrinker = {
164	.shrink = lowmem_shrink,
165	.seeks = DEFAULT_SEEKS * 16
166};
167
168static int __init lowmem_init(void)
169{
170	register_shrinker(&lowmem_shrinker);
171	return 0;
172}
173
174static void __exit lowmem_exit(void)
175{
176	unregister_shrinker(&lowmem_shrinker);
177}
178
179module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
180module_param_array_named(adj, lowmem_adj, short, &lowmem_adj_size,
181			 S_IRUGO | S_IWUSR);
182module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
183			 S_IRUGO | S_IWUSR);
184module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
185
186module_init(lowmem_init);
187module_exit(lowmem_exit);
188
189MODULE_LICENSE("GPL");
190
191