lowmemorykiller.c revision 0984e56a65a29ad0700c5abf657327e73929ea1f 
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_adj values will get killed. Specify the
5 * minimum oom_adj values in /sys/module/lowmemorykiller/parameters/adj and the
6 * number of free pages in /sys/module/lowmemorykiller/parameters/minfree. Both
7 * files take a comma separated list of numbers in ascending order.
8 *
9 * For example, write "0,8" to /sys/module/lowmemorykiller/parameters/adj and
10 * "1024,4096" to /sys/module/lowmemorykiller/parameters/minfree to kill processes
11 * with a oom_adj value of 8 or higher when the free memory drops below 4096 pages
12 * and kill processes with a oom_adj value of 0 or higher when the free memory
13 * drops below 1024 pages.
14 *
15 * The driver considers memory used for caches to be free, but if a large
16 * percentage of the cached memory is locked this can be very inaccurate
17 * and processes may not get killed until the normal oom killer is triggered.
18 *
19 * Copyright (C) 2007-2008 Google, Inc.
20 *
21 * This software is licensed under the terms of the GNU General Public
22 * License version 2, as published by the Free Software Foundation, and
23 * may be copied, distributed, and modified under those terms.
24 *
25 * This program is distributed in the hope that it will be useful,
26 * but WITHOUT ANY WARRANTY; without even the implied warranty of
27 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
28 * GNU General Public License for more details.
29 *
30 */
31
32#include <linux/module.h>
33#include <linux/kernel.h>
34#include <linux/mm.h>
35#include <linux/oom.h>
36#include <linux/sched.h>
37
38static uint32_t lowmem_debug_level = 2;
39static int lowmem_adj[6] = {
40	0,
41	1,
42	6,
43	12,
44};
45static int lowmem_adj_size = 4;
46static size_t lowmem_minfree[6] = {
47	3 * 512,	/* 6MB */
48	2 * 1024,	/* 8MB */
49	4 * 1024,	/* 16MB */
50	16 * 1024,	/* 64MB */
51};
52static int lowmem_minfree_size = 4;
53
54#define lowmem_print(level, x...)			\
55	do {						\
56		if (lowmem_debug_level >= (level))	\
57			printk(x);			\
58	} while (0)
59
60static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask)
61{
62	struct task_struct *p;
63	struct task_struct *selected = NULL;
64	int rem = 0;
65	int tasksize;
66	int i;
67	int min_adj = OOM_ADJUST_MAX + 1;
68	int selected_tasksize = 0;
69	int selected_oom_adj;
70	int array_size = ARRAY_SIZE(lowmem_adj);
71	int other_free = global_page_state(NR_FREE_PAGES);
72	int other_file = global_page_state(NR_FILE_PAGES);
73
74	if (lowmem_adj_size < array_size)
75		array_size = lowmem_adj_size;
76	if (lowmem_minfree_size < array_size)
77		array_size = lowmem_minfree_size;
78	for (i = 0; i < array_size; i++) {
79		if (other_free < lowmem_minfree[i] &&
80		    other_file < lowmem_minfree[i]) {
81			min_adj = lowmem_adj[i];
82			break;
83		}
84	}
85	if (nr_to_scan > 0)
86		lowmem_print(3, "lowmem_shrink %d, %x, ofree %d %d, ma %d\n",
87			     nr_to_scan, gfp_mask, other_free, other_file,
88			     min_adj);
89	rem = global_page_state(NR_ACTIVE_ANON) +
90		global_page_state(NR_ACTIVE_FILE) +
91		global_page_state(NR_INACTIVE_ANON) +
92		global_page_state(NR_INACTIVE_FILE);
93	if (nr_to_scan <= 0 || min_adj == OOM_ADJUST_MAX + 1) {
94		lowmem_print(5, "lowmem_shrink %d, %x, return %d\n",
95			     nr_to_scan, gfp_mask, rem);
96		return rem;
97	}
98	selected_oom_adj = min_adj;
99
100	read_lock(&tasklist_lock);
101	for_each_process(p) {
102		struct mm_struct *mm;
103		int oom_adj;
104
105		task_lock(p);
106		mm = p->mm;
107		if (!mm) {
108			task_unlock(p);
109			continue;
110		}
111		oom_adj = mm->oom_adj;
112		if (oom_adj < min_adj) {
113			task_unlock(p);
114			continue;
115		}
116		tasksize = get_mm_rss(mm);
117		task_unlock(p);
118		if (tasksize <= 0)
119			continue;
120		if (selected) {
121			if (oom_adj < selected_oom_adj)
122				continue;
123			if (oom_adj == selected_oom_adj &&
124			    tasksize <= selected_tasksize)
125				continue;
126		}
127		selected = p;
128		selected_tasksize = tasksize;
129		selected_oom_adj = oom_adj;
130		lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
131			     p->pid, p->comm, oom_adj, tasksize);
132	}
133	if (selected) {
134		lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
135			     selected->pid, selected->comm,
136			     selected_oom_adj, selected_tasksize);
137		force_sig(SIGKILL, selected);
138		rem -= selected_tasksize;
139	}
140	lowmem_print(4, "lowmem_shrink %d, %x, return %d\n",
141		     nr_to_scan, gfp_mask, rem);
142	read_unlock(&tasklist_lock);
143	return rem;
144}
145
146static struct shrinker lowmem_shrinker = {
147	.shrink = lowmem_shrink,
148	.seeks = DEFAULT_SEEKS * 16
149};
150
151static int __init lowmem_init(void)
152{
153	register_shrinker(&lowmem_shrinker);
154	return 0;
155}
156
157static void __exit lowmem_exit(void)
158{
159	unregister_shrinker(&lowmem_shrinker);
160}
161
162module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
163module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size,
164			 S_IRUGO | S_IWUSR);
165module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
166			 S_IRUGO | S_IWUSR);
167module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
168
169module_init(lowmem_init);
170module_exit(lowmem_exit);
171
172MODULE_LICENSE("GPL");
173
174