lowmemorykiller.c revision edd540ea92954f896bfb7ee0ebf5dfdde6e6cb41 
1/* drivers/misc/lowmemorykiller.c
2 *
3 * Copyright (C) 2007-2008 Google, Inc.
4 *
5 * This software is licensed under the terms of the GNU General Public
6 * License version 2, as published by the Free Software Foundation, and
7 * may be copied, distributed, and modified under those terms.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12 * GNU General Public License for more details.
13 *
14 */
15
16#include <linux/module.h>
17#include <linux/kernel.h>
18#include <linux/mm.h>
19#include <linux/oom.h>
20#include <linux/sched.h>
21
22static uint32_t lowmem_debug_level = 2;
23static int lowmem_adj[6] = {
24	0,
25	1,
26	6,
27	12,
28};
29static int lowmem_adj_size = 4;
30static size_t lowmem_minfree[6] = {
31	3 * 512,	/* 6MB */
32	2 * 1024,	/* 8MB */
33	4 * 1024,	/* 16MB */
34	16 * 1024,	/* 64MB */
35};
36static int lowmem_minfree_size = 4;
37
38#define lowmem_print(level, x...)			\
39	do {						\
40		if (lowmem_debug_level >= (level))	\
41			printk(x);			\
42	} while (0)
43
44module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
45module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size,
46			 S_IRUGO | S_IWUSR);
47module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
48			 S_IRUGO | S_IWUSR);
49module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
50
51static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask)
52{
53	struct task_struct *p;
54	struct task_struct *selected = NULL;
55	int rem = 0;
56	int tasksize;
57	int i;
58	int min_adj = OOM_ADJUST_MAX + 1;
59	int selected_tasksize = 0;
60	int selected_oom_adj;
61	int array_size = ARRAY_SIZE(lowmem_adj);
62	int other_free = global_page_state(NR_FREE_PAGES);
63	int other_file = global_page_state(NR_FILE_PAGES);
64
65	if (lowmem_adj_size < array_size)
66		array_size = lowmem_adj_size;
67	if (lowmem_minfree_size < array_size)
68		array_size = lowmem_minfree_size;
69	for (i = 0; i < array_size; i++) {
70		if (other_free < lowmem_minfree[i] &&
71		    other_file < lowmem_minfree[i]) {
72			min_adj = lowmem_adj[i];
73			break;
74		}
75	}
76	if (nr_to_scan > 0)
77		lowmem_print(3, "lowmem_shrink %d, %x, ofree %d %d, ma %d\n",
78			     nr_to_scan, gfp_mask, other_free, other_file,
79			     min_adj);
80	rem = global_page_state(NR_ACTIVE_ANON) +
81		global_page_state(NR_ACTIVE_FILE) +
82		global_page_state(NR_INACTIVE_ANON) +
83		global_page_state(NR_INACTIVE_FILE);
84	if (nr_to_scan <= 0 || min_adj == OOM_ADJUST_MAX + 1) {
85		lowmem_print(5, "lowmem_shrink %d, %x, return %d\n",
86			     nr_to_scan, gfp_mask, rem);
87		return rem;
88	}
89	selected_oom_adj = min_adj;
90
91	read_lock(&tasklist_lock);
92	for_each_process(p) {
93		struct mm_struct *mm;
94		int oom_adj;
95
96		task_lock(p);
97		mm = p->mm;
98		if (!mm) {
99			task_unlock(p);
100			continue;
101		}
102		oom_adj = mm->oom_adj;
103		if (oom_adj < min_adj) {
104			task_unlock(p);
105			continue;
106		}
107		tasksize = get_mm_rss(mm);
108		task_unlock(p);
109		if (tasksize <= 0)
110			continue;
111		if (selected) {
112			if (oom_adj < selected_oom_adj)
113				continue;
114			if (oom_adj == selected_oom_adj &&
115			    tasksize <= selected_tasksize)
116				continue;
117		}
118		selected = p;
119		selected_tasksize = tasksize;
120		selected_oom_adj = oom_adj;
121		lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
122			     p->pid, p->comm, oom_adj, tasksize);
123	}
124	if (selected) {
125		lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
126			     selected->pid, selected->comm,
127			     selected_oom_adj, selected_tasksize);
128		force_sig(SIGKILL, selected);
129		rem -= selected_tasksize;
130	}
131	lowmem_print(4, "lowmem_shrink %d, %x, return %d\n",
132		     nr_to_scan, gfp_mask, rem);
133	read_unlock(&tasklist_lock);
134	return rem;
135}
136
137static struct shrinker lowmem_shrinker = {
138	.shrink = lowmem_shrink,
139	.seeks = DEFAULT_SEEKS * 16
140};
141
142static int __init lowmem_init(void)
143{
144	register_shrinker(&lowmem_shrinker);
145	return 0;
146}
147
148static void __exit lowmem_exit(void)
149{
150	unregister_shrinker(&lowmem_shrinker);
151}
152
153module_init(lowmem_init);
154module_exit(lowmem_exit);
155
156MODULE_LICENSE("GPL");
157
158