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
44#define CREATE_TRACE_POINTS
45#include "trace/lowmemorykiller.h"
46
47static uint32_t lowmem_debug_level = 1;
48static short lowmem_adj[6] = {
49	0,
50	1,
51	6,
52	12,
53};
54static int lowmem_adj_size = 4;
55static int lowmem_minfree[6] = {
56	3 * 512,	/* 6MB */
57	2 * 1024,	/* 8MB */
58	4 * 1024,	/* 16MB */
59	16 * 1024,	/* 64MB */
60};
61static int lowmem_minfree_size = 4;
62
63static unsigned long lowmem_deathpending_timeout;
64
65#define lowmem_print(level, x...)			\
66	do {						\
67		if (lowmem_debug_level >= (level))	\
68			pr_info(x);			\
69	} while (0)
70
71static unsigned long lowmem_count(struct shrinker *s,
72				  struct shrink_control *sc)
73{
74	return global_page_state(NR_ACTIVE_ANON) +
75		global_page_state(NR_ACTIVE_FILE) +
76		global_page_state(NR_INACTIVE_ANON) +
77		global_page_state(NR_INACTIVE_FILE);
78}
79
80static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
81{
82	struct task_struct *tsk;
83	struct task_struct *selected = NULL;
84	unsigned long rem = 0;
85	int tasksize;
86	int i;
87	short min_score_adj = OOM_SCORE_ADJ_MAX + 1;
88	int minfree = 0;
89	int selected_tasksize = 0;
90	short selected_oom_score_adj;
91	int array_size = ARRAY_SIZE(lowmem_adj);
92	int other_free = global_page_state(NR_FREE_PAGES) - totalreserve_pages;
93	int other_file = global_page_state(NR_FILE_PAGES) -
94						global_page_state(NR_SHMEM) -
95						total_swapcache_pages();
96
97	if (lowmem_adj_size < array_size)
98		array_size = lowmem_adj_size;
99	if (lowmem_minfree_size < array_size)
100		array_size = lowmem_minfree_size;
101	for (i = 0; i < array_size; i++) {
102		minfree = lowmem_minfree[i];
103		if (other_free < minfree && other_file < minfree) {
104			min_score_adj = lowmem_adj[i];
105			break;
106		}
107	}
108
109	lowmem_print(3, "lowmem_scan %lu, %x, ofree %d %d, ma %hd\n",
110			sc->nr_to_scan, sc->gfp_mask, other_free,
111			other_file, min_score_adj);
112
113	if (min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
114		lowmem_print(5, "lowmem_scan %lu, %x, return 0\n",
115			     sc->nr_to_scan, sc->gfp_mask);
116		return 0;
117	}
118
119	selected_oom_score_adj = min_score_adj;
120
121	rcu_read_lock();
122	for_each_process(tsk) {
123		struct task_struct *p;
124		short oom_score_adj;
125
126		if (tsk->flags & PF_KTHREAD)
127			continue;
128
129		p = find_lock_task_mm(tsk);
130		if (!p)
131			continue;
132
133		if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
134		    time_before_eq(jiffies, lowmem_deathpending_timeout)) {
135			task_unlock(p);
136			rcu_read_unlock();
137			return 0;
138		}
139		oom_score_adj = p->signal->oom_score_adj;
140		if (oom_score_adj < min_score_adj) {
141			task_unlock(p);
142			continue;
143		}
144		tasksize = get_mm_rss(p->mm);
145		task_unlock(p);
146		if (tasksize <= 0)
147			continue;
148		if (selected) {
149			if (oom_score_adj < selected_oom_score_adj)
150				continue;
151			if (oom_score_adj == selected_oom_score_adj &&
152			    tasksize <= selected_tasksize)
153				continue;
154		}
155		selected = p;
156		selected_tasksize = tasksize;
157		selected_oom_score_adj = oom_score_adj;
158		lowmem_print(2, "select '%s' (%d), adj %hd, size %d, to kill\n",
159			     p->comm, p->pid, oom_score_adj, tasksize);
160	}
161	if (selected) {
162		long cache_size = other_file * (long)(PAGE_SIZE / 1024);
163		long cache_limit = minfree * (long)(PAGE_SIZE / 1024);
164		long free = other_free * (long)(PAGE_SIZE / 1024);
165		trace_lowmemory_kill(selected, cache_size, cache_limit, free);
166		lowmem_print(1, "Killing '%s' (%d), adj %hd,\n" \
167				"   to free %ldkB on behalf of '%s' (%d) because\n" \
168				"   cache %ldkB is below limit %ldkB for oom_score_adj %hd\n" \
169				"   Free memory is %ldkB above reserved\n",
170			     selected->comm, selected->pid,
171			     selected_oom_score_adj,
172			     selected_tasksize * (long)(PAGE_SIZE / 1024),
173			     current->comm, current->pid,
174			     cache_size, cache_limit,
175			     min_score_adj,
176			     free);
177		lowmem_deathpending_timeout = jiffies + HZ;
178		set_tsk_thread_flag(selected, TIF_MEMDIE);
179		send_sig(SIGKILL, selected, 0);
180		rem += selected_tasksize;
181	}
182
183	lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",
184		     sc->nr_to_scan, sc->gfp_mask, rem);
185	rcu_read_unlock();
186	return rem;
187}
188
189static struct shrinker lowmem_shrinker = {
190	.scan_objects = lowmem_scan,
191	.count_objects = lowmem_count,
192	.seeks = DEFAULT_SEEKS * 16
193};
194
195static int __init lowmem_init(void)
196{
197	register_shrinker(&lowmem_shrinker);
198	return 0;
199}
200
201static void __exit lowmem_exit(void)
202{
203	unregister_shrinker(&lowmem_shrinker);
204}
205
206#ifdef CONFIG_ANDROID_LOW_MEMORY_KILLER_AUTODETECT_OOM_ADJ_VALUES
207static short lowmem_oom_adj_to_oom_score_adj(short oom_adj)
208{
209	if (oom_adj == OOM_ADJUST_MAX)
210		return OOM_SCORE_ADJ_MAX;
211	else
212		return (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE;
213}
214
215static void lowmem_autodetect_oom_adj_values(void)
216{
217	int i;
218	short oom_adj;
219	short oom_score_adj;
220	int array_size = ARRAY_SIZE(lowmem_adj);
221
222	if (lowmem_adj_size < array_size)
223		array_size = lowmem_adj_size;
224
225	if (array_size <= 0)
226		return;
227
228	oom_adj = lowmem_adj[array_size - 1];
229	if (oom_adj > OOM_ADJUST_MAX)
230		return;
231
232	oom_score_adj = lowmem_oom_adj_to_oom_score_adj(oom_adj);
233	if (oom_score_adj <= OOM_ADJUST_MAX)
234		return;
235
236	lowmem_print(1, "lowmem_shrink: convert oom_adj to oom_score_adj:\n");
237	for (i = 0; i < array_size; i++) {
238		oom_adj = lowmem_adj[i];
239		oom_score_adj = lowmem_oom_adj_to_oom_score_adj(oom_adj);
240		lowmem_adj[i] = oom_score_adj;
241		lowmem_print(1, "oom_adj %d => oom_score_adj %d\n",
242			     oom_adj, oom_score_adj);
243	}
244}
245
246static int lowmem_adj_array_set(const char *val, const struct kernel_param *kp)
247{
248	int ret;
249
250	ret = param_array_ops.set(val, kp);
251
252	/* HACK: Autodetect oom_adj values in lowmem_adj array */
253	lowmem_autodetect_oom_adj_values();
254
255	return ret;
256}
257
258static int lowmem_adj_array_get(char *buffer, const struct kernel_param *kp)
259{
260	return param_array_ops.get(buffer, kp);
261}
262
263static void lowmem_adj_array_free(void *arg)
264{
265	param_array_ops.free(arg);
266}
267
268static struct kernel_param_ops lowmem_adj_array_ops = {
269	.set = lowmem_adj_array_set,
270	.get = lowmem_adj_array_get,
271	.free = lowmem_adj_array_free,
272};
273
274static const struct kparam_array __param_arr_adj = {
275	.max = ARRAY_SIZE(lowmem_adj),
276	.num = &lowmem_adj_size,
277	.ops = &param_ops_short,
278	.elemsize = sizeof(lowmem_adj[0]),
279	.elem = lowmem_adj,
280};
281#endif
282
283module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
284#ifdef CONFIG_ANDROID_LOW_MEMORY_KILLER_AUTODETECT_OOM_ADJ_VALUES
285module_param_cb(adj, &lowmem_adj_array_ops,
286		.arr = &__param_arr_adj, S_IRUGO | S_IWUSR);
287__MODULE_PARM_TYPE(adj, "array of short");
288#else
289module_param_array_named(adj, lowmem_adj, short, &lowmem_adj_size,
290			 S_IRUGO | S_IWUSR);
291#endif
292module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
293			 S_IRUGO | S_IWUSR);
294module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
295
296module_init(lowmem_init);
297module_exit(lowmem_exit);
298
299MODULE_LICENSE("GPL");
300
301