1 /* drivers/misc/lowmemorykiller.c
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.
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.
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.
20 * Copyright (C) 2007-2008 Google, Inc.
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.
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.
33 #include <linux/module.h>
34 #include <linux/kernel.h>
36 #include <linux/oom.h>
37 #include <linux/sched.h>
38 #include <linux/rcupdate.h>
39 #include <linux/profile.h>
40 #include <linux/notifier.h>
42 static uint32_t lowmem_debug_level = 2;
43 static int lowmem_adj[6] = {
49 static int lowmem_adj_size = 4;
50 static int lowmem_minfree[6] = {
56 static int lowmem_minfree_size = 4;
58 static unsigned long lowmem_deathpending_timeout;
60 #define lowmem_print(level, x...) \
62 if (lowmem_debug_level >= (level)) \
66 static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
68 struct task_struct *tsk;
69 struct task_struct *selected = NULL;
73 int min_score_adj = OOM_SCORE_ADJ_MAX + 1;
74 int selected_tasksize = 0;
75 int selected_oom_score_adj;
76 int array_size = ARRAY_SIZE(lowmem_adj);
77 int other_free = global_page_state(NR_FREE_PAGES);
78 int other_file = global_page_state(NR_FILE_PAGES) -
79 global_page_state(NR_SHMEM);
81 if (lowmem_adj_size < array_size)
82 array_size = lowmem_adj_size;
83 if (lowmem_minfree_size < array_size)
84 array_size = lowmem_minfree_size;
85 for (i = 0; i < array_size; i++) {
86 if (other_free < lowmem_minfree[i] &&
87 other_file < lowmem_minfree[i]) {
88 min_score_adj = lowmem_adj[i];
92 if (sc->nr_to_scan > 0)
93 lowmem_print(3, "lowmem_shrink %lu, %x, ofree %d %d, ma %d\n",
94 sc->nr_to_scan, sc->gfp_mask, other_free,
95 other_file, min_score_adj);
96 rem = global_page_state(NR_ACTIVE_ANON) +
97 global_page_state(NR_ACTIVE_FILE) +
98 global_page_state(NR_INACTIVE_ANON) +
99 global_page_state(NR_INACTIVE_FILE);
100 if (sc->nr_to_scan <= 0 || min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
101 lowmem_print(5, "lowmem_shrink %lu, %x, return %d\n",
102 sc->nr_to_scan, sc->gfp_mask, rem);
105 selected_oom_score_adj = min_score_adj;
108 for_each_process(tsk) {
109 struct task_struct *p;
112 if (tsk->flags & PF_KTHREAD)
115 p = find_lock_task_mm(tsk);
119 if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
120 time_before_eq(jiffies, lowmem_deathpending_timeout)) {
125 oom_score_adj = p->signal->oom_score_adj;
126 if (oom_score_adj < min_score_adj) {
130 tasksize = get_mm_rss(p->mm);
135 if (oom_score_adj < selected_oom_score_adj)
137 if (oom_score_adj == selected_oom_score_adj &&
138 tasksize <= selected_tasksize)
142 selected_tasksize = tasksize;
143 selected_oom_score_adj = oom_score_adj;
144 lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
145 p->pid, p->comm, oom_score_adj, tasksize);
148 lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
149 selected->pid, selected->comm,
150 selected_oom_score_adj, selected_tasksize);
151 lowmem_deathpending_timeout = jiffies + HZ;
152 send_sig(SIGKILL, selected, 0);
153 set_tsk_thread_flag(selected, TIF_MEMDIE);
154 rem -= selected_tasksize;
156 lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
157 sc->nr_to_scan, sc->gfp_mask, rem);
162 static struct shrinker lowmem_shrinker = {
163 .shrink = lowmem_shrink,
164 .seeks = DEFAULT_SEEKS * 16
167 static int __init lowmem_init(void)
169 register_shrinker(&lowmem_shrinker);
173 static void __exit lowmem_exit(void)
175 unregister_shrinker(&lowmem_shrinker);
178 module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
179 module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size,
181 module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
183 module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
185 module_init(lowmem_init);
186 module_exit(lowmem_exit);
188 MODULE_LICENSE("GPL");