lowmemorykiller.c revision 31d59a4198f3f07da8250dfb5b698eacfaf612e5 
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 int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask);
23
24static struct shrinker lowmem_shrinker = {
25	.shrink = lowmem_shrink,
26	.seeks = DEFAULT_SEEKS * 16
27};
28static uint32_t lowmem_debug_level = 2;
29static int lowmem_adj[6] = {
30	0,
31	1,
32	6,
33	12,
34};
35static int lowmem_adj_size = 4;
36static size_t lowmem_minfree[6] = {
37	3*512, // 6MB
38	2*1024, // 8MB
39	4*1024, // 16MB
40	16*1024, // 64MB
41};
42static int lowmem_minfree_size = 4;
43
44#define lowmem_print(level, x...) do { if(lowmem_debug_level >= (level)) printk(x); } while(0)
45
46module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
47module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size, S_IRUGO | S_IWUSR);
48module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size, 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 array_size = ARRAY_SIZE(lowmem_adj);
61	int other_free = global_page_state(NR_FREE_PAGES);
62	int other_file = global_page_state(NR_FILE_PAGES);
63	if(lowmem_adj_size < array_size)
64		array_size = lowmem_adj_size;
65	if(lowmem_minfree_size < array_size)
66		array_size = lowmem_minfree_size;
67	for(i = 0; i < array_size; i++) {
68		if (other_free < lowmem_minfree[i] &&
69		    other_file < lowmem_minfree[i]) {
70			min_adj = lowmem_adj[i];
71			break;
72		}
73	}
74	if(nr_to_scan > 0)
75		lowmem_print(3, "lowmem_shrink %d, %x, ofree %d %d, ma %d\n", nr_to_scan, gfp_mask, other_free, other_file, min_adj);
76	rem = global_page_state(NR_ACTIVE_ANON) +
77		global_page_state(NR_ACTIVE_FILE) +
78		global_page_state(NR_INACTIVE_ANON) +
79		global_page_state(NR_INACTIVE_FILE);
80	if (nr_to_scan <= 0 || min_adj == OOM_ADJUST_MAX + 1) {
81		lowmem_print(5, "lowmem_shrink %d, %x, return %d\n", nr_to_scan, gfp_mask, rem);
82		return rem;
83	}
84
85	read_lock(&tasklist_lock);
86	for_each_process(p) {
87		if (p->oomkilladj < min_adj || !p->mm)
88			continue;
89		tasksize = get_mm_rss(p->mm);
90		if (tasksize <= 0)
91			continue;
92		if (selected) {
93			if (p->oomkilladj < selected->oomkilladj)
94				continue;
95			if (p->oomkilladj == selected->oomkilladj &&
96			    tasksize <= selected_tasksize)
97				continue;
98		}
99		selected = p;
100		selected_tasksize = tasksize;
101		lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
102		             p->pid, p->comm, p->oomkilladj, tasksize);
103	}
104	if(selected != NULL) {
105		lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
106		             selected->pid, selected->comm,
107		             selected->oomkilladj, selected_tasksize);
108		force_sig(SIGKILL, selected);
109		rem -= selected_tasksize;
110	}
111	lowmem_print(4, "lowmem_shrink %d, %x, return %d\n", nr_to_scan, gfp_mask, rem);
112	read_unlock(&tasklist_lock);
113	return rem;
114}
115
116static int __init lowmem_init(void)
117{
118	register_shrinker(&lowmem_shrinker);
119	return 0;
120}
121
122static void __exit lowmem_exit(void)
123{
124	unregister_shrinker(&lowmem_shrinker);
125}
126
127module_init(lowmem_init);
128module_exit(lowmem_exit);
129
130MODULE_LICENSE("GPL");
131
132