lowmemorykiller.c revision 6b83f9150ff5d23355fc3baf6960801fb1525f77 
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
34
35#include <linux/module.h>
36#include <linux/kernel.h>
37#include <linux/mm.h>
38#include <linux/oom.h>
39#include <linux/sched.h>
40#include <linux/swap.h>
41#include <linux/rcupdate.h>
42#include <linux/profile.h>
43#include <linux/notifier.h>
44
45static uint32_t lowmem_debug_level = 1;
46static short lowmem_adj[6] = {
47	0,
48	1,
49	6,
50	12,
51};
52static int lowmem_adj_size = 4;
53static int lowmem_minfree[6] = {
54	3 * 512,	/* 6MB */
55	2 * 1024,	/* 8MB */
56	4 * 1024,	/* 16MB */
57	16 * 1024,	/* 64MB */
58};
59static int lowmem_minfree_size = 4;
60
61static unsigned long lowmem_deathpending_timeout;
62
63#define lowmem_print(level, x...)			\
64	do {						\
65		if (lowmem_debug_level >= (level))	\
66			pr_info(x);			\
67	} while (0)
68
69static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
70{
71	struct task_struct *tsk;
72	struct task_struct *selected = NULL;
73	int rem = 0;
74	int tasksize;
75	int i;
76	short min_score_adj = OOM_SCORE_ADJ_MAX + 1;
77	int selected_tasksize = 0;
78	short selected_oom_score_adj;
79	int array_size = ARRAY_SIZE(lowmem_adj);
80	int other_free = global_page_state(NR_FREE_PAGES) - totalreserve_pages;
81	int other_file = global_page_state(NR_FILE_PAGES) -
82						global_page_state(NR_SHMEM);
83
84	if (lowmem_adj_size < array_size)
85		array_size = lowmem_adj_size;
86	if (lowmem_minfree_size < array_size)
87		array_size = lowmem_minfree_size;
88	for (i = 0; i < array_size; i++) {
89		if (other_free < lowmem_minfree[i] &&
90		    other_file < lowmem_minfree[i]) {
91			min_score_adj = lowmem_adj[i];
92			break;
93		}
94	}
95	if (sc->nr_to_scan > 0)
96		lowmem_print(3, "lowmem_shrink %lu, %x, ofree %d %d, ma %hd\n",
97				sc->nr_to_scan, sc->gfp_mask, other_free,
98				other_file, min_score_adj);
99	rem = global_page_state(NR_ACTIVE_ANON) +
100		global_page_state(NR_ACTIVE_FILE) +
101		global_page_state(NR_INACTIVE_ANON) +
102		global_page_state(NR_INACTIVE_FILE);
103	if (sc->nr_to_scan <= 0 || min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
104		lowmem_print(5, "lowmem_shrink %lu, %x, return %d\n",
105			     sc->nr_to_scan, sc->gfp_mask, rem);
106		return rem;
107	}
108	selected_oom_score_adj = min_score_adj;
109
110	rcu_read_lock();
111	for_each_process(tsk) {
112		struct task_struct *p;
113		short oom_score_adj;
114
115		if (tsk->flags & PF_KTHREAD)
116			continue;
117
118		p = find_lock_task_mm(tsk);
119		if (!p)
120			continue;
121
122		if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
123		    time_before_eq(jiffies, lowmem_deathpending_timeout)) {
124			task_unlock(p);
125			rcu_read_unlock();
126			return 0;
127		}
128		oom_score_adj = p->signal->oom_score_adj;
129		if (oom_score_adj < min_score_adj) {
130			task_unlock(p);
131			continue;
132		}
133		tasksize = get_mm_rss(p->mm);
134		task_unlock(p);
135		if (tasksize <= 0)
136			continue;
137		if (selected) {
138			if (oom_score_adj < selected_oom_score_adj)
139				continue;
140			if (oom_score_adj == selected_oom_score_adj &&
141			    tasksize <= selected_tasksize)
142				continue;
143		}
144		selected = p;
145		selected_tasksize = tasksize;
146		selected_oom_score_adj = oom_score_adj;
147		lowmem_print(2, "select %d (%s), adj %hd, size %d, to kill\n",
148			     p->pid, p->comm, oom_score_adj, tasksize);
149	}
150	if (selected) {
151		lowmem_print(1, "send sigkill to %d (%s), adj %hd, size %d\n",
152			     selected->pid, selected->comm,
153			     selected_oom_score_adj, selected_tasksize);
154		lowmem_deathpending_timeout = jiffies + HZ;
155		send_sig(SIGKILL, selected, 0);
156		set_tsk_thread_flag(selected, TIF_MEMDIE);
157		rem -= selected_tasksize;
158	}
159	lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
160		     sc->nr_to_scan, sc->gfp_mask, rem);
161	rcu_read_unlock();
162	return rem;
163}
164
165static struct shrinker lowmem_shrinker = {
166	.shrink = lowmem_shrink,
167	.seeks = DEFAULT_SEEKS * 16
168};
169
170static int __init lowmem_init(void)
171{
172	register_shrinker(&lowmem_shrinker);
173	return 0;
174}
175
176static void __exit lowmem_exit(void)
177{
178	unregister_shrinker(&lowmem_shrinker);
179}
180
181module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
182module_param_array_named(adj, lowmem_adj, short, &lowmem_adj_size,
183			 S_IRUGO | S_IWUSR);
184module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
185			 S_IRUGO | S_IWUSR);
186module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
187
188module_init(lowmem_init);
189module_exit(lowmem_exit);
190
191MODULE_LICENSE("GPL");
192
193