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/profile.h>
43 #include <linux/notifier.h>
44
45 static uint32_t lowmem_debug_level = 1;
46 static short lowmem_adj[6] = {
47 0,
48 1,
49 6,
50 12,
51 };
52 static int lowmem_adj_size = 4;
53 static int lowmem_minfree[6] = {
54 3 * 512, /* 6MB */
55 2 * 1024, /* 8MB */
56 4 * 1024, /* 16MB */
57 16 * 1024, /* 64MB */
58 };
59 static int lowmem_minfree_size = 4;
60
61 static unsigned long lowmem_deathpending_timeout;
62
63 #define lowmem_print(level, x...) \
64 do { \
65 if (lowmem_debug_level >= (level)) \
66 pr_info(x); \
67 } while (0)
68
lowmem_count(struct shrinker * s,struct shrink_control * sc)69 static unsigned long lowmem_count(struct shrinker *s,
70 struct shrink_control *sc)
71 {
72 return global_page_state(NR_ACTIVE_ANON) +
73 global_page_state(NR_ACTIVE_FILE) +
74 global_page_state(NR_INACTIVE_ANON) +
75 global_page_state(NR_INACTIVE_FILE);
76 }
77
lowmem_scan(struct shrinker * s,struct shrink_control * sc)78 static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
79 {
80 struct task_struct *tsk;
81 struct task_struct *selected = NULL;
82 unsigned long rem = 0;
83 int tasksize;
84 int i;
85 short min_score_adj = OOM_SCORE_ADJ_MAX + 1;
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 if (other_free < lowmem_minfree[i] &&
100 other_file < lowmem_minfree[i]) {
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 %d (%s), adj %hd, size %d, to kill\n",
156 p->pid, p->comm, oom_score_adj, tasksize);
157 }
158 if (selected) {
159 lowmem_print(1, "send sigkill to %d (%s), adj %hd, size %d\n",
160 selected->pid, selected->comm,
161 selected_oom_score_adj, selected_tasksize);
162 lowmem_deathpending_timeout = jiffies + HZ;
163 /*
164 * FIXME: lowmemorykiller shouldn't abuse global OOM killer
165 * infrastructure. There is no real reason why the selected
166 * task should have access to the memory reserves.
167 */
168 mark_tsk_oom_victim(selected);
169 send_sig(SIGKILL, selected, 0);
170 rem += selected_tasksize;
171 }
172
173 lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",
174 sc->nr_to_scan, sc->gfp_mask, rem);
175 rcu_read_unlock();
176 return rem;
177 }
178
179 static struct shrinker lowmem_shrinker = {
180 .scan_objects = lowmem_scan,
181 .count_objects = lowmem_count,
182 .seeks = DEFAULT_SEEKS * 16
183 };
184
lowmem_init(void)185 static int __init lowmem_init(void)
186 {
187 register_shrinker(&lowmem_shrinker);
188 return 0;
189 }
190
lowmem_exit(void)191 static void __exit lowmem_exit(void)
192 {
193 unregister_shrinker(&lowmem_shrinker);
194 }
195
196 module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
197 module_param_array_named(adj, lowmem_adj, short, &lowmem_adj_size,
198 S_IRUGO | S_IWUSR);
199 module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
200 S_IRUGO | S_IWUSR);
201 module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
202
203 module_init(lowmem_init);
204 module_exit(lowmem_exit);
205
206 MODULE_LICENSE("GPL");
207
208