lowmemorykiller.c revision 5d14a573a4da521d4ed7acd0c7d8a975887b2dd2 
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 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		int oom_adj;
94
95		task_lock(p);
96		if (!p->mm) {
97			task_unlock(p);
98			continue;
99		}
100		oom_adj = p->oomkilladj;
101		if (oom_adj < min_adj) {
102			task_unlock(p);
103			continue;
104		}
105		tasksize = get_mm_rss(p->mm);
106		task_unlock(p);
107		if (tasksize <= 0)
108			continue;
109		if (selected) {
110			if (oom_adj < selected_oom_adj)
111				continue;
112			if (oom_adj == selected_oom_adj &&
113			    tasksize <= selected_tasksize)
114				continue;
115		}
116		selected = p;
117		selected_tasksize = tasksize;
118		selected_oom_adj = oom_adj;
119		lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
120		             p->pid, p->comm, oom_adj, tasksize);
121	}
122	if (selected) {
123		lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
124		             selected->pid, selected->comm,
125		             selected_oom_adj, selected_tasksize);
126		force_sig(SIGKILL, selected);
127		rem -= selected_tasksize;
128	}
129	lowmem_print(4, "lowmem_shrink %d, %x, return %d\n",
130		     nr_to_scan, gfp_mask, rem);
131	read_unlock(&tasklist_lock);
132	return rem;
133}
134
135static int __init lowmem_init(void)
136{
137	register_shrinker(&lowmem_shrinker);
138	return 0;
139}
140
141static void __exit lowmem_exit(void)
142{
143	unregister_shrinker(&lowmem_shrinker);
144}
145
146module_init(lowmem_init);
147module_exit(lowmem_exit);
148
149MODULE_LICENSE("GPL");
150
151