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_node_page_state(NR_ACTIVE_ANON
) +
76 global_node_page_state(NR_ACTIVE_FILE
) +
77 global_node_page_state(NR_INACTIVE_ANON
) +
78 global_node_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_node_page_state(NR_FILE_PAGES
) -
95 global_node_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
);