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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
35 #include <linux/init.h>
36 #include <linux/moduleparam.h>
37 #include <linux/kernel.h>
39 #include <linux/oom.h>
40 #include <linux/sched.h>
41 #include <linux/swap.h>
42 #include <linux/rcupdate.h>
43 #include <linux/profile.h>
44 #include <linux/notifier.h>
46 static u32 lowmem_debug_level = 1;
47 static short lowmem_adj[6] = {
54 static int lowmem_adj_size = 4;
55 static int lowmem_minfree[6] = {
62 static int lowmem_minfree_size = 4;
64 static unsigned long lowmem_deathpending_timeout;
66 #define lowmem_print(level, x...) \
68 if (lowmem_debug_level >= (level)) \
72 static unsigned long lowmem_count(struct shrinker *s,
73 struct shrink_control *sc)
75 return global_page_state(NR_ACTIVE_ANON) +
76 global_page_state(NR_ACTIVE_FILE) +
77 global_page_state(NR_INACTIVE_ANON) +
78 global_page_state(NR_INACTIVE_FILE);
81 static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
83 struct task_struct *tsk;
84 struct task_struct *selected = NULL;
85 unsigned long rem = 0;
88 short min_score_adj = OOM_SCORE_ADJ_MAX + 1;
90 int selected_tasksize = 0;
91 short selected_oom_score_adj;
92 int array_size = ARRAY_SIZE(lowmem_adj);
93 int other_free = global_page_state(NR_FREE_PAGES) - totalreserve_pages;
94 int other_file = global_page_state(NR_FILE_PAGES) -
95 global_page_state(NR_SHMEM) -
96 total_swapcache_pages();
98 if (lowmem_adj_size < array_size)
99 array_size = lowmem_adj_size;
100 if (lowmem_minfree_size < array_size)
101 array_size = lowmem_minfree_size;
102 for (i = 0; i < array_size; i++) {
103 minfree = lowmem_minfree[i];
104 if (other_free < minfree && other_file < minfree) {
105 min_score_adj = lowmem_adj[i];
110 lowmem_print(3, "lowmem_scan %lu, %x, ofree %d %d, ma %hd\n",
111 sc->nr_to_scan, sc->gfp_mask, other_free,
112 other_file, min_score_adj);
114 if (min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
115 lowmem_print(5, "lowmem_scan %lu, %x, return 0\n",
116 sc->nr_to_scan, sc->gfp_mask);
120 selected_oom_score_adj = min_score_adj;
123 for_each_process(tsk) {
124 struct task_struct *p;
127 if (tsk->flags & PF_KTHREAD)
130 p = find_lock_task_mm(tsk);
134 if (task_lmk_waiting(p) &&
135 time_before_eq(jiffies, lowmem_deathpending_timeout)) {
140 oom_score_adj = p->signal->oom_score_adj;
141 if (oom_score_adj < min_score_adj) {
145 tasksize = get_mm_rss(p->mm);
150 if (oom_score_adj < selected_oom_score_adj)
152 if (oom_score_adj == selected_oom_score_adj &&
153 tasksize <= selected_tasksize)
157 selected_tasksize = tasksize;
158 selected_oom_score_adj = oom_score_adj;
159 lowmem_print(2, "select '%s' (%d), adj %hd, size %d, to kill\n",
160 p->comm, p->pid, oom_score_adj, tasksize);
164 send_sig(SIGKILL, selected, 0);
166 task_set_lmk_waiting(selected);
167 task_unlock(selected);
168 lowmem_print(1, "Killing '%s' (%d), adj %hd,\n"
169 " to free %ldkB on behalf of '%s' (%d) because\n"
170 " cache %ldkB is below limit %ldkB for oom_score_adj %hd\n"
171 " Free memory is %ldkB above reserved\n",
172 selected->comm, selected->pid,
173 selected_oom_score_adj,
174 selected_tasksize * (long)(PAGE_SIZE / 1024),
175 current->comm, current->pid,
176 other_file * (long)(PAGE_SIZE / 1024),
177 minfree * (long)(PAGE_SIZE / 1024),
179 other_free * (long)(PAGE_SIZE / 1024));
180 lowmem_deathpending_timeout = jiffies + HZ;
181 rem += selected_tasksize;
184 lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",
185 sc->nr_to_scan, sc->gfp_mask, rem);
190 static struct shrinker lowmem_shrinker = {
191 .scan_objects = lowmem_scan,
192 .count_objects = lowmem_count,
193 .seeks = DEFAULT_SEEKS * 16
196 static int __init lowmem_init(void)
198 register_shrinker(&lowmem_shrinker);
201 device_initcall(lowmem_init);
204 * not really modular, but the easiest way to keep compat with existing
205 * bootargs behaviour is to continue using module_param here.
207 module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
208 module_param_array_named(adj, lowmem_adj, short, &lowmem_adj_size,
210 module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
212 module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);