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   1 /* drivers/misc/lowmemorykiller.c
   2  *
   3  * Copyright (C) 2007-2008 Google, Inc.
   4  *
   5  * This software is licensed under the terms of the GNU General Public
   6  * License version 2, as published by the Free Software Foundation, and
   7  * may be copied, distributed, and modified under those terms.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/kernel.h>
  18 #include <linux/mm.h>
  19 #include <linux/oom.h>
  20 #include <linux/sched.h>
  21
  22 static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask);
  23
  24 static struct shrinker lowmem_shrinker = {
  25         .shrink = lowmem_shrink,
  26         .seeks = DEFAULT_SEEKS * 16
  27 };
  28 static uint32_t lowmem_debug_level = 2;
  29 static int lowmem_adj[6] = {
  30         0,
  31         1,
  32         6,
  33         12,
  34 };
  35 static int lowmem_adj_size = 4;
  36 static size_t lowmem_minfree[6] = {
  37         3*512, // 6MB
  38         2*1024, // 8MB
  39         4*1024, // 16MB
  40         16*1024, // 64MB
  41 };
  42 static int lowmem_minfree_size = 4;
  43
  44 #define lowmem_print(level, x...) do { if(lowmem_debug_level >= (level)) printk(x); } while(0)
  45
  46 module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
  47 module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size, S_IRUGO | S_IWUSR);
  48 module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size, S_IRUGO | S_IWUSR);
  49 module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
  50
  51 static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask)
  52 {
  53         struct task_struct *p;
  54         struct task_struct *selected = NULL;
  55         int rem = 0;
  56         int tasksize;
  57         int i;
  58         int min_adj = OOM_ADJUST_MAX + 1;
  59         int selected_tasksize = 0;
  60         int selected_oom_adj;
  61         int array_size = ARRAY_SIZE(lowmem_adj);
  62         int other_free = global_page_state(NR_FREE_PAGES);
  63         int other_file = global_page_state(NR_FILE_PAGES);
  64
  65         if (lowmem_adj_size < array_size)
  66                 array_size = lowmem_adj_size;
  67         if (lowmem_minfree_size < array_size)
  68                 array_size = lowmem_minfree_size;
  69         for (i = 0; i < array_size; i++) {
  70                 if (other_free < lowmem_minfree[i] &&
  71                     other_file < lowmem_minfree[i]) {
  72                         min_adj = lowmem_adj[i];
  73                         break;
  74                 }
  75         }
  76         if (nr_to_scan > 0)
  77                 lowmem_print(3, "lowmem_shrink %d, %x, ofree %d %d, ma %d\n",
  78                              nr_to_scan, gfp_mask, other_free, other_file,
  79                              min_adj);
  80         rem = global_page_state(NR_ACTIVE_ANON) +
  81                 global_page_state(NR_ACTIVE_FILE) +
  82                 global_page_state(NR_INACTIVE_ANON) +
  83                 global_page_state(NR_INACTIVE_FILE);
  84         if (nr_to_scan <= 0 || min_adj == OOM_ADJUST_MAX + 1) {
  85                 lowmem_print(5, "lowmem_shrink %d, %x, return %d\n",
  86                              nr_to_scan, gfp_mask, rem);
  87                 return rem;
  88         }
  89         selected_oom_adj = min_adj;
  90
  91         read_lock(&tasklist_lock);
  92         for_each_process(p) {
  93                 int oom_adj;
  94
  95                 if (!p->mm)
  96                         continue;
  97                 oom_adj = p->oomkilladj;
  98                 if (oom_adj < min_adj)
  99                         continue;
 100                 tasksize = get_mm_rss(p->mm);
 101                 if (tasksize <= 0)
 102                         continue;
 103                 if (selected) {
 104                         if (oom_adj < selected_oom_adj)
 105                                 continue;
 106                         if (oom_adj == selected_oom_adj &&
 107                             tasksize <= selected_tasksize)
 108                                 continue;
 109                 }
 110                 selected = p;
 111                 selected_tasksize = tasksize;
 112                 selected_oom_adj = oom_adj;
 113                 lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
 114                              p->pid, p->comm, oom_adj, tasksize);
 115         }
 116         if (selected) {
 117                 lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
 118                              selected->pid, selected->comm,
 119                              selected_oom_adj, selected_tasksize);
 120                 force_sig(SIGKILL, selected);
 121                 rem -= selected_tasksize;
 122         }
 123         lowmem_print(4, "lowmem_shrink %d, %x, return %d\n",
 124                      nr_to_scan, gfp_mask, rem);
 125         read_unlock(&tasklist_lock);
 126         return rem;
 127 }
 128
 129 static int __init lowmem_init(void)
 130 {
 131         register_shrinker(&lowmem_shrinker);
 132         return 0;
 133 }
 134
 135 static void __exit lowmem_exit(void)
 136 {
 137         unregister_shrinker(&lowmem_shrinker);
 138 }
 139
 140 module_init(lowmem_init);
 141 module_exit(lowmem_exit);
 142
 143 MODULE_LICENSE("GPL");
 144