lowmemorykiller.c revision 71b2c82bdf67ab24716c536e10de436169d3574c 
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#include <linux/profile.h>
38#include <linux/notifier.h>
39
40static uint32_t lowmem_debug_level = 2;
41static int lowmem_adj[6] = {
42	0,
43	1,
44	6,
45	12,
46};
47static int lowmem_adj_size = 4;
48static size_t lowmem_minfree[6] = {
49	3 * 512,	/* 6MB */
50	2 * 1024,	/* 8MB */
51	4 * 1024,	/* 16MB */
52	16 * 1024,	/* 64MB */
53};
54static int lowmem_minfree_size = 4;
55
56static struct task_struct *lowmem_deathpending;
57
58#define lowmem_print(level, x...)			\
59	do {						\
60		if (lowmem_debug_level >= (level))	\
61			printk(x);			\
62	} while (0)
63
64static int
65task_notify_func(struct notifier_block *self, unsigned long val, void *data);
66
67static struct notifier_block task_nb = {
68	.notifier_call	= task_notify_func,
69};
70
71static int
72task_notify_func(struct notifier_block *self, unsigned long val, void *data)
73{
74	struct task_struct *task = data;
75	if (task == lowmem_deathpending) {
76		lowmem_deathpending = NULL;
77		task_handoff_unregister(&task_nb);
78	}
79	return NOTIFY_OK;
80}
81
82static int lowmem_shrink(struct shrinker *s, int nr_to_scan, gfp_t gfp_mask)
83{
84	struct task_struct *p;
85	struct task_struct *selected = NULL;
86	int rem = 0;
87	int tasksize;
88	int i;
89	int min_adj = OOM_ADJUST_MAX + 1;
90	int selected_tasksize = 0;
91	int selected_oom_adj;
92	int array_size = ARRAY_SIZE(lowmem_adj);
93	int other_free = global_page_state(NR_FREE_PAGES);
94	int other_file = global_page_state(NR_FILE_PAGES) -
95						global_page_state(NR_SHMEM);
96
97	/*
98	 * If we already have a death outstanding, then
99	 * bail out right away; indicating to vmscan
100	 * that we have nothing further to offer on
101	 * this pass.
102	 *
103	 * Note: Currently you need CONFIG_PROFILING
104	 * for this to work correctly.
105	 */
106	if (lowmem_deathpending)
107		return 0;
108
109	if (lowmem_adj_size < array_size)
110		array_size = lowmem_adj_size;
111	if (lowmem_minfree_size < array_size)
112		array_size = lowmem_minfree_size;
113	for (i = 0; i < array_size; i++) {
114		if (other_free < lowmem_minfree[i] &&
115		    other_file < lowmem_minfree[i]) {
116			min_adj = lowmem_adj[i];
117			break;
118		}
119	}
120	if (nr_to_scan > 0)
121		lowmem_print(3, "lowmem_shrink %d, %x, ofree %d %d, ma %d\n",
122			     nr_to_scan, gfp_mask, other_free, other_file,
123			     min_adj);
124	rem = global_page_state(NR_ACTIVE_ANON) +
125		global_page_state(NR_ACTIVE_FILE) +
126		global_page_state(NR_INACTIVE_ANON) +
127		global_page_state(NR_INACTIVE_FILE);
128	if (nr_to_scan <= 0 || min_adj == OOM_ADJUST_MAX + 1) {
129		lowmem_print(5, "lowmem_shrink %d, %x, return %d\n",
130			     nr_to_scan, gfp_mask, rem);
131		return rem;
132	}
133	selected_oom_adj = min_adj;
134
135	read_lock(&tasklist_lock);
136	for_each_process(p) {
137		struct mm_struct *mm;
138		struct signal_struct *sig;
139		int oom_adj;
140
141		task_lock(p);
142		mm = p->mm;
143		sig = p->signal;
144		if (!mm || !sig) {
145			task_unlock(p);
146			continue;
147		}
148		oom_adj = sig->oom_adj;
149		if (oom_adj < min_adj) {
150			task_unlock(p);
151			continue;
152		}
153		tasksize = get_mm_rss(mm);
154		task_unlock(p);
155		if (tasksize <= 0)
156			continue;
157		if (selected) {
158			if (oom_adj < selected_oom_adj)
159				continue;
160			if (oom_adj == selected_oom_adj &&
161			    tasksize <= selected_tasksize)
162				continue;
163		}
164		selected = p;
165		selected_tasksize = tasksize;
166		selected_oom_adj = oom_adj;
167		lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
168			     p->pid, p->comm, oom_adj, tasksize);
169	}
170	if (selected) {
171		lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
172			     selected->pid, selected->comm,
173			     selected_oom_adj, selected_tasksize);
174		/*
175		 * If CONFIG_PROFILING is off, then task_handoff_register()
176		 * is a nop. In that case we don't want to stall the killer
177		 * by setting lowmem_deathpending.
178		 */
179#ifdef CONFIG_PROFILING
180		lowmem_deathpending = selected;
181		task_handoff_register(&task_nb);
182#endif
183		force_sig(SIGKILL, selected);
184		rem -= selected_tasksize;
185	}
186	lowmem_print(4, "lowmem_shrink %d, %x, return %d\n",
187		     nr_to_scan, gfp_mask, rem);
188	read_unlock(&tasklist_lock);
189	return rem;
190}
191
192static struct shrinker lowmem_shrinker = {
193	.shrink = lowmem_shrink,
194	.seeks = DEFAULT_SEEKS * 16
195};
196
197static int __init lowmem_init(void)
198{
199	register_shrinker(&lowmem_shrinker);
200	return 0;
201}
202
203static void __exit lowmem_exit(void)
204{
205	unregister_shrinker(&lowmem_shrinker);
206}
207
208module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
209module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size,
210			 S_IRUGO | S_IWUSR);
211module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
212			 S_IRUGO | S_IWUSR);
213module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
214
215module_init(lowmem_init);
216module_exit(lowmem_exit);
217
218MODULE_LICENSE("GPL");
219
220