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_adj values will get killed. Specify the
5 * minimum oom_adj values in /sys/module/lowmemorykiller/parameters/adj and the
6 * number of free pages in /sys/module/lowmemorykiller/parameters/minfree. Both
7 * files take a comma separated list of numbers in ascending order.
8 *
9 * For example, write "0,8" to /sys/module/lowmemorykiller/parameters/adj and
10 * "1024,4096" to /sys/module/lowmemorykiller/parameters/minfree to kill
11 * processes with a oom_adj value of 8 or higher when the free memory drops
12 * below 4096 pages and kill processes with a oom_adj value of 0 or higher
13 * when the free memory drops below 1024 pages.
14 *
15 * The driver considers memory used for caches to be free, but if a large
16 * percentage of the cached memory is locked this can be very inaccurate
17 * and processes may not get killed until the normal oom killer is triggered.
18 *
19 * Copyright (C) 2007-2008 Google, Inc.
20 *
21 * This software is licensed under the terms of the GNU General Public
22 * License version 2, as published by the Free Software Foundation, and
23 * may be copied, distributed, and modified under those terms.
24 *
25 * This program is distributed in the hope that it will be useful,
26 * but WITHOUT ANY WARRANTY; without even the implied warranty of
27 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
28 * GNU General Public License for more details.
29 *
30 */
31
32 #include <linux/module.h>
33 #include <linux/kernel.h>
34 #include <linux/mm.h>
35 #include <linux/oom.h>
36 #include <linux/sched.h>
37 #include <linux/profile.h>
38 #include <linux/notifier.h>
39
40 static uint32_t lowmem_debug_level = 2;
41 static int lowmem_adj[6] = {
42 0,
43 1,
44 6,
45 12,
46 };
47 static int lowmem_adj_size = 4;
48 static size_t lowmem_minfree[6] = {
49 3 * 512, /* 6MB */
50 2 * 1024, /* 8MB */
51 4 * 1024, /* 16MB */
52 16 * 1024, /* 64MB */
53 };
54 static int lowmem_minfree_size = 4;
55
56 static struct task_struct *lowmem_deathpending;
57 static unsigned long lowmem_deathpending_timeout;
58
59 #define lowmem_print(level, x...) \
60 do { \
61 if (lowmem_debug_level >= (level)) \
62 printk(x); \
63 } while (0)
64
65 static int
66 task_notify_func(struct notifier_block *self, unsigned long val, void *data);
67
68 static struct notifier_block task_nb = {
69 .notifier_call = task_notify_func,
70 };
71
72 static int
task_notify_func(struct notifier_block * self,unsigned long val,void * data)73 task_notify_func(struct notifier_block *self, unsigned long val, void *data)
74 {
75 struct task_struct *task = data;
76 if (task == lowmem_deathpending) {
77 lowmem_deathpending = NULL;
78 task_handoff_unregister(&task_nb);
79 }
80 return NOTIFY_OK;
81 }
82
lowmem_shrink(struct shrinker * s,struct shrink_control * sc)83 static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
84 {
85 struct task_struct *p;
86 struct task_struct *selected = NULL;
87 int rem = 0;
88 int tasksize;
89 int i;
90 int min_adj = OOM_ADJUST_MAX + 1;
91 int selected_tasksize = 0;
92 int selected_oom_adj;
93 int array_size = ARRAY_SIZE(lowmem_adj);
94 int other_free = global_page_state(NR_FREE_PAGES);
95 int other_file = global_page_state(NR_FILE_PAGES) -
96 global_page_state(NR_SHMEM);
97
98 /*
99 * If we already have a death outstanding, then
100 * bail out right away; indicating to vmscan
101 * that we have nothing further to offer on
102 * this pass.
103 *
104 * Note: Currently you need CONFIG_PROFILING
105 * for this to work correctly.
106 */
107 if (lowmem_deathpending &&
108 time_before_eq(jiffies, lowmem_deathpending_timeout))
109 return 0;
110
111 if (lowmem_adj_size < array_size)
112 array_size = lowmem_adj_size;
113 if (lowmem_minfree_size < array_size)
114 array_size = lowmem_minfree_size;
115 for (i = 0; i < array_size; i++) {
116 if (other_free < lowmem_minfree[i] &&
117 other_file < lowmem_minfree[i]) {
118 min_adj = lowmem_adj[i];
119 break;
120 }
121 }
122 if (sc->nr_to_scan > 0)
123 lowmem_print(3, "lowmem_shrink %lu, %x, ofree %d %d, ma %d\n",
124 sc->nr_to_scan, sc->gfp_mask, other_free,
125 other_file, min_adj);
126 rem = global_page_state(NR_ACTIVE_ANON) +
127 global_page_state(NR_ACTIVE_FILE) +
128 global_page_state(NR_INACTIVE_ANON) +
129 global_page_state(NR_INACTIVE_FILE);
130 if (sc->nr_to_scan <= 0 || min_adj == OOM_ADJUST_MAX + 1) {
131 lowmem_print(5, "lowmem_shrink %lu, %x, return %d\n",
132 sc->nr_to_scan, sc->gfp_mask, rem);
133 return rem;
134 }
135 selected_oom_adj = min_adj;
136
137 read_lock(&tasklist_lock);
138 for_each_process(p) {
139 struct mm_struct *mm;
140 struct signal_struct *sig;
141 int oom_adj;
142
143 task_lock(p);
144 mm = p->mm;
145 sig = p->signal;
146 if (!mm || !sig) {
147 task_unlock(p);
148 continue;
149 }
150 oom_adj = sig->oom_adj;
151 if (oom_adj < min_adj) {
152 task_unlock(p);
153 continue;
154 }
155 tasksize = get_mm_rss(mm);
156 task_unlock(p);
157 if (tasksize <= 0)
158 continue;
159 if (selected) {
160 if (oom_adj < selected_oom_adj)
161 continue;
162 if (oom_adj == selected_oom_adj &&
163 tasksize <= selected_tasksize)
164 continue;
165 }
166 selected = p;
167 selected_tasksize = tasksize;
168 selected_oom_adj = oom_adj;
169 lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
170 p->pid, p->comm, oom_adj, tasksize);
171 }
172 if (selected) {
173 lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
174 selected->pid, selected->comm,
175 selected_oom_adj, selected_tasksize);
176 /*
177 * If CONFIG_PROFILING is off, then task_handoff_register()
178 * is a nop. In that case we don't want to stall the killer
179 * by setting lowmem_deathpending.
180 */
181 #ifdef CONFIG_PROFILING
182 lowmem_deathpending = selected;
183 lowmem_deathpending_timeout = jiffies + HZ;
184 task_handoff_register(&task_nb);
185 #endif
186 force_sig(SIGKILL, selected);
187 rem -= selected_tasksize;
188 }
189 lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
190 sc->nr_to_scan, sc->gfp_mask, rem);
191 read_unlock(&tasklist_lock);
192 return rem;
193 }
194
195 static struct shrinker lowmem_shrinker = {
196 .shrink = lowmem_shrink,
197 .seeks = DEFAULT_SEEKS * 16
198 };
199
lowmem_init(void)200 static int __init lowmem_init(void)
201 {
202 register_shrinker(&lowmem_shrinker);
203 return 0;
204 }
205
lowmem_exit(void)206 static void __exit lowmem_exit(void)
207 {
208 unregister_shrinker(&lowmem_shrinker);
209 }
210
211 module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
212 module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size,
213 S_IRUGO | S_IWUSR);
214 module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
215 S_IRUGO | S_IWUSR);
216 module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
217
218 module_init(lowmem_init);
219 module_exit(lowmem_exit);
220
221 MODULE_LICENSE("GPL");
222
223