lowmemorykiller.c revision 1dbb5765acc7a6fe4bc1957c001037cc9d02ae03 
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...)			\
45	do {						\
46		if (lowmem_debug_level >= (level))	\
47			printk(x);			\
48	} while (0)
49
50module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
51module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size,
52			 S_IRUGO | S_IWUSR);
53module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
54			 S_IRUGO | S_IWUSR);
55module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
56
57static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask)
58{
59	struct task_struct *p;
60	struct task_struct *selected = NULL;
61	int rem = 0;
62	int tasksize;
63	int i;
64	int min_adj = OOM_ADJUST_MAX + 1;
65	int selected_tasksize = 0;
66	int selected_oom_adj;
67	int array_size = ARRAY_SIZE(lowmem_adj);
68	int other_free = global_page_state(NR_FREE_PAGES);
69	int other_file = global_page_state(NR_FILE_PAGES);
70
71	if (lowmem_adj_size < array_size)
72		array_size = lowmem_adj_size;
73	if (lowmem_minfree_size < array_size)
74		array_size = lowmem_minfree_size;
75	for (i = 0; i < array_size; i++) {
76		if (other_free < lowmem_minfree[i] &&
77		    other_file < lowmem_minfree[i]) {
78			min_adj = lowmem_adj[i];
79			break;
80		}
81	}
82	if (nr_to_scan > 0)
83		lowmem_print(3, "lowmem_shrink %d, %x, ofree %d %d, ma %d\n",
84			     nr_to_scan, gfp_mask, other_free, other_file,
85			     min_adj);
86	rem = global_page_state(NR_ACTIVE_ANON) +
87		global_page_state(NR_ACTIVE_FILE) +
88		global_page_state(NR_INACTIVE_ANON) +
89		global_page_state(NR_INACTIVE_FILE);
90	if (nr_to_scan <= 0 || min_adj == OOM_ADJUST_MAX + 1) {
91		lowmem_print(5, "lowmem_shrink %d, %x, return %d\n",
92			     nr_to_scan, gfp_mask, rem);
93		return rem;
94	}
95	selected_oom_adj = min_adj;
96
97	read_lock(&tasklist_lock);
98	for_each_process(p) {
99		int oom_adj;
100
101		task_lock(p);
102		if (!p->mm) {
103			task_unlock(p);
104			continue;
105		}
106		oom_adj = p->oomkilladj;
107		if (oom_adj < min_adj) {
108			task_unlock(p);
109			continue;
110		}
111		tasksize = get_mm_rss(p->mm);
112		task_unlock(p);
113		if (tasksize <= 0)
114			continue;
115		if (selected) {
116			if (oom_adj < selected_oom_adj)
117				continue;
118			if (oom_adj == selected_oom_adj &&
119			    tasksize <= selected_tasksize)
120				continue;
121		}
122		selected = p;
123		selected_tasksize = tasksize;
124		selected_oom_adj = oom_adj;
125		lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
126			     p->pid, p->comm, oom_adj, tasksize);
127	}
128	if (selected) {
129		lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
130			     selected->pid, selected->comm,
131			     selected_oom_adj, selected_tasksize);
132		force_sig(SIGKILL, selected);
133		rem -= selected_tasksize;
134	}
135	lowmem_print(4, "lowmem_shrink %d, %x, return %d\n",
136		     nr_to_scan, gfp_mask, rem);
137	read_unlock(&tasklist_lock);
138	return rem;
139}
140
141static int __init lowmem_init(void)
142{
143	register_shrinker(&lowmem_shrinker);
144	return 0;
145}
146
147static void __exit lowmem_exit(void)
148{
149	unregister_shrinker(&lowmem_shrinker);
150}
151
152module_init(lowmem_init);
153module_exit(lowmem_exit);
154
155MODULE_LICENSE("GPL");
156
157