drivers/staging/android/lowmemorykiller.c

   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 array_size = ARRAY_SIZE(lowmem_adj);
  61         int other_free = global_page_state(NR_FREE_PAGES) + global_page_state(NR_FILE_PAGES);
  62         if(lowmem_adj_size < array_size)
  63                 array_size = lowmem_adj_size;
  64         if(lowmem_minfree_size < array_size)
  65                 array_size = lowmem_minfree_size;
  66         for(i = 0; i < array_size; i++) {
  67                 if(other_free < lowmem_minfree[i]) {
  68                         min_adj = lowmem_adj[i];
  69                         break;
  70                 }
  71         }
  72         if(nr_to_scan > 0)
  73                 lowmem_print(3, "lowmem_shrink %d, %x, ofree %d, ma %d\n", nr_to_scan, gfp_mask, other_free, min_adj);
  74         read_lock(&tasklist_lock);
  75         for_each_process(p) {
  76                 if(p->oomkilladj >= 0 && p->mm) {
  77                         tasksize = get_mm_rss(p->mm);
  78                         if(nr_to_scan > 0 && tasksize > 0 && p->oomkilladj >= min_adj) {
  79                                 if(selected == NULL ||
  80                                    p->oomkilladj > selected->oomkilladj ||
  81                                    (p->oomkilladj == selected->oomkilladj &&
  82                                     tasksize > selected_tasksize)) {
  83                                         selected = p;
  84                                         selected_tasksize = tasksize;
  85                                         lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
  86                                                      p->pid, p->comm, p->oomkilladj, tasksize);
  87                                 }
  88                         }
  89                         rem += tasksize;
  90                 }
  91         }
  92         if(selected != NULL) {
  93                 lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
  94                              selected->pid, selected->comm,
  95                              selected->oomkilladj, selected_tasksize);
  96                 force_sig(SIGKILL, selected);
  97                 rem -= selected_tasksize;
  98         }
  99         lowmem_print(4, "lowmem_shrink %d, %x, return %d\n", nr_to_scan, gfp_mask, rem);
 100         read_unlock(&tasklist_lock);
 101         return rem;
 102 }
 103
 104 static int __init lowmem_init(void)
 105 {
 106         register_shrinker(&lowmem_shrinker);
 107         return 0;
 108 }
 109
 110 static void __exit lowmem_exit(void)
 111 {
 112         unregister_shrinker(&lowmem_shrinker);
 113 }
 114
 115 module_init(lowmem_init);
 116 module_exit(lowmem_exit);
 117
 118 MODULE_LICENSE("GPL");
 119