/drivers/staging/android/lowmemorykiller.c

  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/notifier.h>
 38
 39static uint32_t lowmem_debug_level = 2;
 40static int lowmem_adj[6] = {
 41	0,
 42	1,
 43	6,
 44	12,
 45};
 46static int lowmem_adj_size = 4;
 47static size_t lowmem_minfree[6] = {
 48	3 * 512,	/* 6MB */
 49	2 * 1024,	/* 8MB */
 50	4 * 1024,	/* 16MB */
 51	16 * 1024,	/* 64MB */
 52};
 53static int lowmem_minfree_size = 4;
 54
 55static struct task_struct *lowmem_deathpending;
 56static unsigned long lowmem_deathpending_timeout;
 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
 76	if (task == lowmem_deathpending)
 77		lowmem_deathpending = NULL;
 78
 79	return NOTIFY_OK;
 80}
 81
 82static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
 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	 */
104	if (lowmem_deathpending &&
105	    time_before_eq(jiffies, lowmem_deathpending_timeout))
106		return 0;
107
108	if (lowmem_adj_size < array_size)
109		array_size = lowmem_adj_size;
110	if (lowmem_minfree_size < array_size)
111		array_size = lowmem_minfree_size;
112	for (i = 0; i < array_size; i++) {
113		if (other_free < lowmem_minfree[i] &&
114		    other_file < lowmem_minfree[i]) {
115			min_adj = lowmem_adj[i];
116			break;
117		}
118	}
119	if (sc->nr_to_scan > 0)
120		lowmem_print(3, "lowmem_shrink %lu, %x, ofree %d %d, ma %d\n",
121			     sc->nr_to_scan, sc->gfp_mask, other_free, other_file,
122			     min_adj);
123	rem = global_page_state(NR_ACTIVE_ANON) +
124		global_page_state(NR_ACTIVE_FILE) +
125		global_page_state(NR_INACTIVE_ANON) +
126		global_page_state(NR_INACTIVE_FILE);
127	if (sc->nr_to_scan <= 0 || min_adj == OOM_ADJUST_MAX + 1) {
128		lowmem_print(5, "lowmem_shrink %lu, %x, return %d\n",
129			     sc->nr_to_scan, sc->gfp_mask, rem);
130		return rem;
131	}
132	selected_oom_adj = min_adj;
133
134	read_lock(&tasklist_lock);
135	for_each_process(p) {
136		struct mm_struct *mm;
137		struct signal_struct *sig;
138		int oom_adj;
139
140		task_lock(p);
141		mm = p->mm;
142		sig = p->signal;
143		if (!mm || !sig) {
144			task_unlock(p);
145			continue;
146		}
147		oom_adj = sig->oom_adj;
148		if (oom_adj < min_adj) {
149			task_unlock(p);
150			continue;
151		}
152		tasksize = get_mm_rss(mm);
153		task_unlock(p);
154		if (tasksize <= 0)
155			continue;
156		if (selected) {
157			if (oom_adj < selected_oom_adj)
158				continue;
159			if (oom_adj == selected_oom_adj &&
160			    tasksize <= selected_tasksize)
161				continue;
162		}
163		selected = p;
164		selected_tasksize = tasksize;
165		selected_oom_adj = oom_adj;
166		lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
167			     p->pid, p->comm, oom_adj, tasksize);
168	}
169	if (selected) {
170		lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
171			     selected->pid, selected->comm,
172			     selected_oom_adj, selected_tasksize);
173		lowmem_deathpending = selected;
174		lowmem_deathpending_timeout = jiffies + HZ;
175		force_sig(SIGKILL, selected);
176		rem -= selected_tasksize;
177	}
178	lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
179		     sc->nr_to_scan, sc->gfp_mask, rem);
180	read_unlock(&tasklist_lock);
181	return rem;
182}
183
184static struct shrinker lowmem_shrinker = {
185	.shrink = lowmem_shrink,
186	.seeks = DEFAULT_SEEKS * 16
187};
188
189static int __init lowmem_init(void)
190{
191	task_free_register(&task_nb);
192	register_shrinker(&lowmem_shrinker);
193	return 0;
194}
195
196static void __exit lowmem_exit(void)
197{
198	unregister_shrinker(&lowmem_shrinker);
199	task_free_unregister(&task_nb);
200}
201
202module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
203module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size,
204			 S_IRUGO | S_IWUSR);
205module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
206			 S_IRUGO | S_IWUSR);
207module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
208
209module_init(lowmem_init);
210module_exit(lowmem_exit);
211
212MODULE_LICENSE("GPL");
213