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/* drivers/misc/lowmemorykiller.c
*
* The lowmemorykiller driver lets user-space specify a set of memory thresholds
* where processes with a range of oom_score_adj values will get killed. Specify
* the minimum oom_score_adj values in
* /sys/module/lowmemorykiller/parameters/adj and the number of free pages in
* /sys/module/lowmemorykiller/parameters/minfree. Both files take a comma
* separated list of numbers in ascending order.
*
* For example, write "0,8" to /sys/module/lowmemorykiller/parameters/adj and
* "1024,4096" to /sys/module/lowmemorykiller/parameters/minfree to kill
* processes with a oom_score_adj value of 8 or higher when the free memory
* drops below 4096 pages and kill processes with a oom_score_adj value of 0 or
* higher when the free memory drops below 1024 pages.
*
* The driver considers memory used for caches to be free, but if a large
* percentage of the cached memory is locked this can be very inaccurate
* and processes may not get killed until the normal oom killer is triggered.
*
* Copyright (C) 2007-2008 Google, Inc.
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/oom.h>
#include <linux/sched.h>
#include <linux/swap.h>
#include <linux/rcupdate.h>
#include <linux/profile.h>
#include <linux/notifier.h>
static uint32_t lowmem_debug_level = 1;
static short lowmem_adj[6] = {
0,
1,
6,
12,
};
static int lowmem_adj_size = 4;
static int lowmem_minfree[6] = {
3 * 512, /* 6MB */
2 * 1024, /* 8MB */
4 * 1024, /* 16MB */
16 * 1024, /* 64MB */
};
static int lowmem_minfree_size = 4;
static unsigned long lowmem_deathpending_timeout;
#define lowmem_print(level, x...) \
do { \
if (lowmem_debug_level >= (level)) \
pr_info(x); \
} while (0)
static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
{
struct task_struct *tsk;
struct task_struct *selected = NULL;
int rem = 0;
int tasksize;
int i;
short min_score_adj = OOM_SCORE_ADJ_MAX + 1;
int selected_tasksize = 0;
short selected_oom_score_adj;
int array_size = ARRAY_SIZE(lowmem_adj);
int other_free = global_page_state(NR_FREE_PAGES) - totalreserve_pages;
int other_file = global_page_state(NR_FILE_PAGES) -
global_page_state(NR_SHMEM);
if (lowmem_adj_size < array_size)
array_size = lowmem_adj_size;
if (lowmem_minfree_size < array_size)
array_size = lowmem_minfree_size;
for (i = 0; i < array_size; i++) {
if (other_free < lowmem_minfree[i] &&
other_file < lowmem_minfree[i]) {
min_score_adj = lowmem_adj[i];
break;
}
}
if (sc->nr_to_scan > 0)
lowmem_print(3, "lowmem_shrink %lu, %x, ofree %d %d, ma %hd\n",
sc->nr_to_scan, sc->gfp_mask, other_free,
other_file, min_score_adj);
rem = global_page_state(NR_ACTIVE_ANON) +
global_page_state(NR_ACTIVE_FILE) +
global_page_state(NR_INACTIVE_ANON) +
global_page_state(NR_INACTIVE_FILE);
if (sc->nr_to_scan <= 0 || min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
lowmem_print(5, "lowmem_shrink %lu, %x, return %d\n",
sc->nr_to_scan, sc->gfp_mask, rem);
return rem;
}
selected_oom_score_adj = min_score_adj;
rcu_read_lock();
for_each_process(tsk) {
struct task_struct *p;
short oom_score_adj;
if (tsk->flags & PF_KTHREAD)
continue;
p = find_lock_task_mm(tsk);
if (!p)
continue;
if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
time_before_eq(jiffies, lowmem_deathpending_timeout)) {
task_unlock(p);
rcu_read_unlock();
return 0;
}
oom_score_adj = p->signal->oom_score_adj;
if (oom_score_adj < min_score_adj) {
task_unlock(p);
continue;
}
tasksize = get_mm_rss(p->mm);
task_unlock(p);
if (tasksize <= 0)
continue;
if (selected) {
if (oom_score_adj < selected_oom_score_adj)
continue;
if (oom_score_adj == selected_oom_score_adj &&
tasksize <= selected_tasksize)
continue;
}
selected = p;
selected_tasksize = tasksize;
selected_oom_score_adj = oom_score_adj;
lowmem_print(2, "select %d (%s), adj %hd, size %d, to kill\n",
p->pid, p->comm, oom_score_adj, tasksize);
}
if (selected) {
lowmem_print(1, "send sigkill to %d (%s), adj %hd, size %d\n",
selected->pid, selected->comm,
selected_oom_score_adj, selected_tasksize);
lowmem_deathpending_timeout = jiffies + HZ;
send_sig(SIGKILL, selected, 0);
set_tsk_thread_flag(selected, TIF_MEMDIE);
rem -= selected_tasksize;
}
lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
sc->nr_to_scan, sc->gfp_mask, rem);
rcu_read_unlock();
return rem;
}
static struct shrinker lowmem_shrinker = {
.shrink = lowmem_shrink,
.seeks = DEFAULT_SEEKS * 16
};
static int __init lowmem_init(void)
{
register_shrinker(&lowmem_shrinker);
return 0;
}
static void __exit lowmem_exit(void)
{
unregister_shrinker(&lowmem_shrinker);
}
module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
module_param_array_named(adj, lowmem_adj, short, &lowmem_adj_size,
S_IRUGO | S_IWUSR);
module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
S_IRUGO | S_IWUSR);
module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
module_init(lowmem_init);
module_exit(lowmem_exit);
MODULE_LICENSE("GPL");
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