Linux Kernel  3.7.1
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lowmemorykiller.c
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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 #include <linux/module.h>
34 #include <linux/kernel.h>
35 #include <linux/mm.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>
41 
42 static uint32_t lowmem_debug_level = 2;
43 static int lowmem_adj[6] = {
44  0,
45  1,
46  6,
47  12,
48 };
49 static int lowmem_adj_size = 4;
50 static int lowmem_minfree[6] = {
51  3 * 512, /* 6MB */
52  2 * 1024, /* 8MB */
53  4 * 1024, /* 16MB */
54  16 * 1024, /* 64MB */
55 };
56 static int lowmem_minfree_size = 4;
57 
58 static unsigned long lowmem_deathpending_timeout;
59 
60 #define lowmem_print(level, x...) \
61  do { \
62  if (lowmem_debug_level >= (level)) \
63  printk(x); \
64  } while (0)
65 
66 static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
67 {
68  struct task_struct *tsk;
69  struct task_struct *selected = NULL;
70  int rem = 0;
71  int tasksize;
72  int i;
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);
80 
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];
89  break;
90  }
91  }
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);
103  return rem;
104  }
105  selected_oom_score_adj = min_score_adj;
106 
107  rcu_read_lock();
108  for_each_process(tsk) {
109  struct task_struct *p;
110  int oom_score_adj;
111 
112  if (tsk->flags & PF_KTHREAD)
113  continue;
114 
115  p = find_lock_task_mm(tsk);
116  if (!p)
117  continue;
118 
119  if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
120  time_before_eq(jiffies, lowmem_deathpending_timeout)) {
121  task_unlock(p);
122  rcu_read_unlock();
123  return 0;
124  }
125  oom_score_adj = p->signal->oom_score_adj;
126  if (oom_score_adj < min_score_adj) {
127  task_unlock(p);
128  continue;
129  }
130  tasksize = get_mm_rss(p->mm);
131  task_unlock(p);
132  if (tasksize <= 0)
133  continue;
134  if (selected) {
135  if (oom_score_adj < selected_oom_score_adj)
136  continue;
137  if (oom_score_adj == selected_oom_score_adj &&
138  tasksize <= selected_tasksize)
139  continue;
140  }
141  selected = p;
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);
146  }
147  if (selected) {
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;
155  }
156  lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
157  sc->nr_to_scan, sc->gfp_mask, rem);
158  rcu_read_unlock();
159  return rem;
160 }
161 
162 static struct shrinker lowmem_shrinker = {
163  .shrink = lowmem_shrink,
164  .seeks = DEFAULT_SEEKS * 16
165 };
166 
167 static int __init lowmem_init(void)
168 {
169  register_shrinker(&lowmem_shrinker);
170  return 0;
171 }
172 
173 static void __exit lowmem_exit(void)
174 {
175  unregister_shrinker(&lowmem_shrinker);
176 }
177 
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,
180  S_IRUGO | S_IWUSR);
181 module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
182  S_IRUGO | S_IWUSR);
183 module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
184 
185 module_init(lowmem_init);
186 module_exit(lowmem_exit);
187 
188 MODULE_LICENSE("GPL");
189