lowmemorykiller.c revision bad385c687f886ef7371628cb239aca6e408708c 
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_score_adj values will get killed. Specify
5 * the minimum oom_score_adj values in
6 * /sys/module/lowmemorykiller/parameters/adj and the number of free pages in
7 * /sys/module/lowmemorykiller/parameters/minfree. Both files take a comma
8 * separated list of numbers in ascending order.
9 *
10 * For example, write "0,8" to /sys/module/lowmemorykiller/parameters/adj and
11 * "1024,4096" to /sys/module/lowmemorykiller/parameters/minfree to kill
12 * processes with a oom_score_adj value of 8 or higher when the free memory
13 * drops below 4096 pages and kill processes with a oom_score_adj value of 0 or
14 * higher when the free memory drops below 1024 pages.
15 *
16 * The driver considers memory used for caches to be free, but if a large
17 * percentage of the cached memory is locked this can be very inaccurate
18 * and processes may not get killed until the normal oom killer is triggered.
19 *
20 * Copyright (C) 2007-2008 Google, Inc.
21 *
22 * This software is licensed under the terms of the GNU General Public
23 * License version 2, as published by the Free Software Foundation, and
24 * may be copied, distributed, and modified under those terms.
25 *
26 * This program is distributed in the hope that it will be useful,
27 * but WITHOUT ANY WARRANTY; without even the implied warranty of
28 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
29 * GNU General Public License for more details.
30 *
31 */
32
33#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
34
35#include <linux/module.h>
36#include <linux/kernel.h>
37#include <linux/mm.h>
38#include <linux/oom.h>
39#include <linux/sched.h>
40#include <linux/swap.h>
41#include <linux/rcupdate.h>
42#include <linux/notifier.h>
43
44static uint32_t lowmem_debug_level = 1;
45static short lowmem_adj[6] = {
46	0,
47	1,
48	6,
49	12,
50};
51static int lowmem_adj_size = 4;
52static int lowmem_minfree[6] = {
53	3 * 512,	/* 6MB */
54	2 * 1024,	/* 8MB */
55	4 * 1024,	/* 16MB */
56	16 * 1024,	/* 64MB */
57};
58static int lowmem_minfree_size = 4;
59
60static unsigned long lowmem_deathpending_timeout;
61
62#define lowmem_print(level, x...)			\
63	do {						\
64		if (lowmem_debug_level >= (level))	\
65			pr_info(x);			\
66	} while (0)
67
68static unsigned long lowmem_count(struct shrinker *s,
69				  struct shrink_control *sc)
70{
71	return global_page_state(NR_ACTIVE_ANON) +
72		global_page_state(NR_ACTIVE_FILE) +
73		global_page_state(NR_INACTIVE_ANON) +
74		global_page_state(NR_INACTIVE_FILE);
75}
76
77static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
78{
79	struct task_struct *tsk;
80	struct task_struct *selected = NULL;
81	unsigned long rem = 0;
82	int tasksize;
83	int i;
84	short min_score_adj = OOM_SCORE_ADJ_MAX + 1;
85	int minfree = 0;
86	int selected_tasksize = 0;
87	short selected_oom_score_adj;
88	int array_size = ARRAY_SIZE(lowmem_adj);
89	int other_free = global_page_state(NR_FREE_PAGES) - totalreserve_pages;
90	int other_file = global_page_state(NR_FILE_PAGES) -
91						global_page_state(NR_SHMEM) -
92						total_swapcache_pages();
93
94	if (lowmem_adj_size < array_size)
95		array_size = lowmem_adj_size;
96	if (lowmem_minfree_size < array_size)
97		array_size = lowmem_minfree_size;
98	for (i = 0; i < array_size; i++) {
99		minfree = lowmem_minfree[i];
100		if (other_free < minfree && other_file < minfree) {
101			min_score_adj = lowmem_adj[i];
102			break;
103		}
104	}
105
106	lowmem_print(3, "lowmem_scan %lu, %x, ofree %d %d, ma %hd\n",
107			sc->nr_to_scan, sc->gfp_mask, other_free,
108			other_file, min_score_adj);
109
110	if (min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
111		lowmem_print(5, "lowmem_scan %lu, %x, return 0\n",
112			     sc->nr_to_scan, sc->gfp_mask);
113		return 0;
114	}
115
116	selected_oom_score_adj = min_score_adj;
117
118	rcu_read_lock();
119	for_each_process(tsk) {
120		struct task_struct *p;
121		short oom_score_adj;
122
123		if (tsk->flags & PF_KTHREAD)
124			continue;
125
126		p = find_lock_task_mm(tsk);
127		if (!p)
128			continue;
129
130		if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
131		    time_before_eq(jiffies, lowmem_deathpending_timeout)) {
132			task_unlock(p);
133			rcu_read_unlock();
134			return 0;
135		}
136		oom_score_adj = p->signal->oom_score_adj;
137		if (oom_score_adj < min_score_adj) {
138			task_unlock(p);
139			continue;
140		}
141		tasksize = get_mm_rss(p->mm);
142		task_unlock(p);
143		if (tasksize <= 0)
144			continue;
145		if (selected) {
146			if (oom_score_adj < selected_oom_score_adj)
147				continue;
148			if (oom_score_adj == selected_oom_score_adj &&
149			    tasksize <= selected_tasksize)
150				continue;
151		}
152		selected = p;
153		selected_tasksize = tasksize;
154		selected_oom_score_adj = oom_score_adj;
155		lowmem_print(2, "select '%s' (%d), adj %hd, size %d, to kill\n",
156			     p->comm, p->pid, oom_score_adj, tasksize);
157	}
158	if (selected) {
159		lowmem_print(1, "Killing '%s' (%d), adj %hd,\n" \
160				"   to free %ldkB on behalf of '%s' (%d) because\n" \
161				"   cache %ldkB is below limit %ldkB for oom_score_adj %hd\n" \
162				"   Free memory is %ldkB above reserved\n",
163			     selected->comm, selected->pid,
164			     selected_oom_score_adj,
165			     selected_tasksize * (long)(PAGE_SIZE / 1024),
166			     current->comm, current->pid,
167			     other_file * (long)(PAGE_SIZE / 1024),
168			     minfree * (long)(PAGE_SIZE / 1024),
169			     min_score_adj,
170			     other_free * (long)(PAGE_SIZE / 1024));
171		lowmem_deathpending_timeout = jiffies + HZ;
172		set_tsk_thread_flag(selected, TIF_MEMDIE);
173		send_sig(SIGKILL, selected, 0);
174		rem += selected_tasksize;
175	}
176
177	lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",
178		     sc->nr_to_scan, sc->gfp_mask, rem);
179	rcu_read_unlock();
180	return rem;
181}
182
183static struct shrinker lowmem_shrinker = {
184	.scan_objects = lowmem_scan,
185	.count_objects = lowmem_count,
186	.seeks = DEFAULT_SEEKS * 16
187};
188
189static int __init lowmem_init(void)
190{
191	register_shrinker(&lowmem_shrinker);
192	return 0;
193}
194
195static void __exit lowmem_exit(void)
196{
197	unregister_shrinker(&lowmem_shrinker);
198}
199
200#ifdef CONFIG_ANDROID_LOW_MEMORY_KILLER_AUTODETECT_OOM_ADJ_VALUES
201static short lowmem_oom_adj_to_oom_score_adj(short oom_adj)
202{
203	if (oom_adj == OOM_ADJUST_MAX)
204		return OOM_SCORE_ADJ_MAX;
205	else
206		return (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE;
207}
208
209static void lowmem_autodetect_oom_adj_values(void)
210{
211	int i;
212	short oom_adj;
213	short oom_score_adj;
214	int array_size = ARRAY_SIZE(lowmem_adj);
215
216	if (lowmem_adj_size < array_size)
217		array_size = lowmem_adj_size;
218
219	if (array_size <= 0)
220		return;
221
222	oom_adj = lowmem_adj[array_size - 1];
223	if (oom_adj > OOM_ADJUST_MAX)
224		return;
225
226	oom_score_adj = lowmem_oom_adj_to_oom_score_adj(oom_adj);
227	if (oom_score_adj <= OOM_ADJUST_MAX)
228		return;
229
230	lowmem_print(1, "lowmem_shrink: convert oom_adj to oom_score_adj:\n");
231	for (i = 0; i < array_size; i++) {
232		oom_adj = lowmem_adj[i];
233		oom_score_adj = lowmem_oom_adj_to_oom_score_adj(oom_adj);
234		lowmem_adj[i] = oom_score_adj;
235		lowmem_print(1, "oom_adj %d => oom_score_adj %d\n",
236			     oom_adj, oom_score_adj);
237	}
238}
239
240static int lowmem_adj_array_set(const char *val, const struct kernel_param *kp)
241{
242	int ret;
243
244	ret = param_array_ops.set(val, kp);
245
246	/* HACK: Autodetect oom_adj values in lowmem_adj array */
247	lowmem_autodetect_oom_adj_values();
248
249	return ret;
250}
251
252static int lowmem_adj_array_get(char *buffer, const struct kernel_param *kp)
253{
254	return param_array_ops.get(buffer, kp);
255}
256
257static void lowmem_adj_array_free(void *arg)
258{
259	param_array_ops.free(arg);
260}
261
262static struct kernel_param_ops lowmem_adj_array_ops = {
263	.set = lowmem_adj_array_set,
264	.get = lowmem_adj_array_get,
265	.free = lowmem_adj_array_free,
266};
267
268static const struct kparam_array __param_arr_adj = {
269	.max = ARRAY_SIZE(lowmem_adj),
270	.num = &lowmem_adj_size,
271	.ops = &param_ops_short,
272	.elemsize = sizeof(lowmem_adj[0]),
273	.elem = lowmem_adj,
274};
275#endif
276
277module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
278#ifdef CONFIG_ANDROID_LOW_MEMORY_KILLER_AUTODETECT_OOM_ADJ_VALUES
279__module_param_call(MODULE_PARAM_PREFIX, adj,
280		    &lowmem_adj_array_ops,
281		    .arr = &__param_arr_adj,
282		    S_IRUGO | S_IWUSR, -1);
283__MODULE_PARM_TYPE(adj, "array of short");
284#else
285module_param_array_named(adj, lowmem_adj, short, &lowmem_adj_size,
286			 S_IRUGO | S_IWUSR);
287#endif
288module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
289			 S_IRUGO | S_IWUSR);
290module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
291
292module_init(lowmem_init);
293module_exit(lowmem_exit);
294
295MODULE_LICENSE("GPL");
296
297