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32#include <linux/module.h>
33#include <linux/kernel.h>
34#include <linux/mm.h>
35#include <linux/oom.h>
36#include <linux/sched.h>
37
38static uint32_t lowmem_debug_level = 2;
39static int lowmem_adj[6] = {
40 0,
41 1,
42 6,
43 12,
44};
45static int lowmem_adj_size = 4;
46static size_t lowmem_minfree[6] = {
47 3 * 512,
48 2 * 1024,
49 4 * 1024,
50 16 * 1024,
51};
52static int lowmem_minfree_size = 4;
53
54#define lowmem_print(level, x...) \
55 do { \
56 if (lowmem_debug_level >= (level)) \
57 printk(x); \
58 } while (0)
59
60static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask)
61{
62 struct task_struct *p;
63 struct task_struct *selected = NULL;
64 int rem = 0;
65 int tasksize;
66 int i;
67 int min_adj = OOM_ADJUST_MAX + 1;
68 int selected_tasksize = 0;
69 int selected_oom_adj;
70 int array_size = ARRAY_SIZE(lowmem_adj);
71 int other_free = global_page_state(NR_FREE_PAGES);
72 int other_file = global_page_state(NR_FILE_PAGES);
73
74 if (lowmem_adj_size < array_size)
75 array_size = lowmem_adj_size;
76 if (lowmem_minfree_size < array_size)
77 array_size = lowmem_minfree_size;
78 for (i = 0; i < array_size; i++) {
79 if (other_free < lowmem_minfree[i] &&
80 other_file < lowmem_minfree[i]) {
81 min_adj = lowmem_adj[i];
82 break;
83 }
84 }
85 if (nr_to_scan > 0)
86 lowmem_print(3, "lowmem_shrink %d, %x, ofree %d %d, ma %d\n",
87 nr_to_scan, gfp_mask, other_free, other_file,
88 min_adj);
89 rem = global_page_state(NR_ACTIVE_ANON) +
90 global_page_state(NR_ACTIVE_FILE) +
91 global_page_state(NR_INACTIVE_ANON) +
92 global_page_state(NR_INACTIVE_FILE);
93 if (nr_to_scan <= 0 || min_adj == OOM_ADJUST_MAX + 1) {
94 lowmem_print(5, "lowmem_shrink %d, %x, return %d\n",
95 nr_to_scan, gfp_mask, rem);
96 return rem;
97 }
98 selected_oom_adj = min_adj;
99
100 read_lock(&tasklist_lock);
101 for_each_process(p) {
102 struct mm_struct *mm;
103 int oom_adj;
104
105 task_lock(p);
106 mm = p->mm;
107 if (!mm) {
108 task_unlock(p);
109 continue;
110 }
111 oom_adj = mm->oom_adj;
112 if (oom_adj < min_adj) {
113 task_unlock(p);
114 continue;
115 }
116 tasksize = get_mm_rss(mm);
117 task_unlock(p);
118 if (tasksize <= 0)
119 continue;
120 if (selected) {
121 if (oom_adj < selected_oom_adj)
122 continue;
123 if (oom_adj == selected_oom_adj &&
124 tasksize <= selected_tasksize)
125 continue;
126 }
127 selected = p;
128 selected_tasksize = tasksize;
129 selected_oom_adj = oom_adj;
130 lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
131 p->pid, p->comm, oom_adj, tasksize);
132 }
133 if (selected) {
134 lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
135 selected->pid, selected->comm,
136 selected_oom_adj, selected_tasksize);
137 force_sig(SIGKILL, selected);
138 rem -= selected_tasksize;
139 }
140 lowmem_print(4, "lowmem_shrink %d, %x, return %d\n",
141 nr_to_scan, gfp_mask, rem);
142 read_unlock(&tasklist_lock);
143 return rem;
144}
145
146static struct shrinker lowmem_shrinker = {
147 .shrink = lowmem_shrink,
148 .seeks = DEFAULT_SEEKS * 16
149};
150
151static int __init lowmem_init(void)
152{
153 register_shrinker(&lowmem_shrinker);
154 return 0;
155}
156
157static void __exit lowmem_exit(void)
158{
159 unregister_shrinker(&lowmem_shrinker);
160}
161
162module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
163module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size,
164 S_IRUGO | S_IWUSR);
165module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
166 S_IRUGO | S_IWUSR);
167module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
168
169module_init(lowmem_init);
170module_exit(lowmem_exit);
171
172MODULE_LICENSE("GPL");
173
174
