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/* drivers/misc/lowmemorykiller.c
*
* 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.
*
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/oom.h>
#include <linux/sched.h>
static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask);
static struct shrinker lowmem_shrinker = {
.shrink = lowmem_shrink,
.seeks = DEFAULT_SEEKS * 16
};
static uint32_t lowmem_debug_level = 2;
static int lowmem_adj[6] = {
0,
1,
6,
12,
};
static int lowmem_adj_size = 4;
static size_t lowmem_minfree[6] = {
3*512, // 6MB
2*1024, // 8MB
4*1024, // 16MB
16*1024, // 64MB
};
static int lowmem_minfree_size = 4;
#define lowmem_print(level, x...) do { if(lowmem_debug_level >= (level)) printk(x); } while(0)
module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
module_param_array_named(adj, lowmem_adj, int, &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);
static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask)
{
struct task_struct *p;
struct task_struct *selected = NULL;
int rem = 0;
int tasksize;
int i;
int min_adj = OOM_ADJUST_MAX + 1;
int selected_tasksize = 0;
int array_size = ARRAY_SIZE(lowmem_adj);
int other_free = global_page_state(NR_FREE_PAGES) + global_page_state(NR_FILE_PAGES);
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]) {
min_adj = lowmem_adj[i];
break;
}
}
if(nr_to_scan > 0)
lowmem_print(3, "lowmem_shrink %d, %x, ofree %d, ma %d\n", nr_to_scan, gfp_mask, other_free, min_adj);
read_lock(&tasklist_lock);
for_each_process(p) {
if(p->oomkilladj >= 0 && p->mm) {
tasksize = get_mm_rss(p->mm);
if(nr_to_scan > 0 && tasksize > 0 && p->oomkilladj >= min_adj) {
if(selected == NULL ||
p->oomkilladj > selected->oomkilladj ||
(p->oomkilladj == selected->oomkilladj &&
tasksize > selected_tasksize)) {
selected = p;
selected_tasksize = tasksize;
lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
p->pid, p->comm, p->oomkilladj, tasksize);
}
}
rem += tasksize;
}
}
if(selected != NULL) {
lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
selected->pid, selected->comm,
selected->oomkilladj, selected_tasksize);
force_sig(SIGKILL, selected);
rem -= selected_tasksize;
}
lowmem_print(4, "lowmem_shrink %d, %x, return %d\n", nr_to_scan, gfp_mask, rem);
read_unlock(&tasklist_lock);
return rem;
}
static int __init lowmem_init(void)
{
register_shrinker(&lowmem_shrinker);
return 0;
}
static void __exit lowmem_exit(void)
{
unregister_shrinker(&lowmem_shrinker);
}
module_init(lowmem_init);
module_exit(lowmem_exit);
MODULE_LICENSE("GPL");
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