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33#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
34
35#include <linux/module.h>
36#include <linux/kernel.h>
37#include <linux/mm.h>
38#include <linux/oom.h>
39#include <linux/sched.h>
40#include <linux/swap.h>
41#include <linux/rcupdate.h>
42#include <linux/profile.h>
43#include <linux/notifier.h>
44
45static uint32_t lowmem_debug_level = 1;
46static short lowmem_adj[6] = {
47 0,
48 1,
49 6,
50 12,
51};
52static int lowmem_adj_size = 4;
53static int lowmem_minfree[6] = {
54 3 * 512,
55 2 * 1024,
56 4 * 1024,
57 16 * 1024,
58};
59static int lowmem_minfree_size = 4;
60
61static unsigned long lowmem_deathpending_timeout;
62
63#define lowmem_print(level, x...) \
64 do { \
65 if (lowmem_debug_level >= (level)) \
66 pr_info(x); \
67 } while (0)
68
69static unsigned long lowmem_count(struct shrinker *s,
70 struct shrink_control *sc)
71{
72 return global_page_state(NR_ACTIVE_ANON) +
73 global_page_state(NR_ACTIVE_FILE) +
74 global_page_state(NR_INACTIVE_ANON) +
75 global_page_state(NR_INACTIVE_FILE);
76}
77
78static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
79{
80 struct task_struct *tsk;
81 struct task_struct *selected = NULL;
82 unsigned long rem = 0;
83 int tasksize;
84 int i;
85 short min_score_adj = OOM_SCORE_ADJ_MAX + 1;
86 int selected_tasksize = 0;
87 short selected_oom_score_adj;
88 int array_size = ARRAY_SIZE(lowmem_adj);
89 int other_free = global_page_state(NR_FREE_PAGES) - totalreserve_pages;
90 int other_file = global_page_state(NR_FILE_PAGES) -
91 global_page_state(NR_SHMEM);
92
93 if (lowmem_adj_size < array_size)
94 array_size = lowmem_adj_size;
95 if (lowmem_minfree_size < array_size)
96 array_size = lowmem_minfree_size;
97 for (i = 0; i < array_size; i++) {
98 if (other_free < lowmem_minfree[i] &&
99 other_file < lowmem_minfree[i]) {
100 min_score_adj = lowmem_adj[i];
101 break;
102 }
103 }
104
105 lowmem_print(3, "lowmem_scan %lu, %x, ofree %d %d, ma %hd\n",
106 sc->nr_to_scan, sc->gfp_mask, other_free,
107 other_file, min_score_adj);
108
109 if (min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
110 lowmem_print(5, "lowmem_scan %lu, %x, return 0\n",
111 sc->nr_to_scan, sc->gfp_mask);
112 return 0;
113 }
114
115 selected_oom_score_adj = min_score_adj;
116
117 rcu_read_lock();
118 for_each_process(tsk) {
119 struct task_struct *p;
120 short oom_score_adj;
121
122 if (tsk->flags & PF_KTHREAD)
123 continue;
124
125 p = find_lock_task_mm(tsk);
126 if (!p)
127 continue;
128
129 if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
130 time_before_eq(jiffies, lowmem_deathpending_timeout)) {
131 task_unlock(p);
132 rcu_read_unlock();
133 return 0;
134 }
135 oom_score_adj = p->signal->oom_score_adj;
136 if (oom_score_adj < min_score_adj) {
137 task_unlock(p);
138 continue;
139 }
140 tasksize = get_mm_rss(p->mm);
141 task_unlock(p);
142 if (tasksize <= 0)
143 continue;
144 if (selected) {
145 if (oom_score_adj < selected_oom_score_adj)
146 continue;
147 if (oom_score_adj == selected_oom_score_adj &&
148 tasksize <= selected_tasksize)
149 continue;
150 }
151 selected = p;
152 selected_tasksize = tasksize;
153 selected_oom_score_adj = oom_score_adj;
154 lowmem_print(2, "select %d (%s), adj %hd, size %d, to kill\n",
155 p->pid, p->comm, oom_score_adj, tasksize);
156 }
157 if (selected) {
158 lowmem_print(1, "send sigkill to %d (%s), adj %hd, size %d\n",
159 selected->pid, selected->comm,
160 selected_oom_score_adj, selected_tasksize);
161 lowmem_deathpending_timeout = jiffies + HZ;
162 send_sig(SIGKILL, selected, 0);
163 set_tsk_thread_flag(selected, TIF_MEMDIE);
164 rem += selected_tasksize;
165 }
166
167 lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",
168 sc->nr_to_scan, sc->gfp_mask, rem);
169 rcu_read_unlock();
170 return rem;
171}
172
173static struct shrinker lowmem_shrinker = {
174 .scan_objects = lowmem_scan,
175 .count_objects = lowmem_count,
176 .seeks = DEFAULT_SEEKS * 16
177};
178
179static int __init lowmem_init(void)
180{
181 register_shrinker(&lowmem_shrinker);
182 return 0;
183}
184
185static void __exit lowmem_exit(void)
186{
187 unregister_shrinker(&lowmem_shrinker);
188}
189
190module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
191module_param_array_named(adj, lowmem_adj, short, &lowmem_adj_size,
192 S_IRUGO | S_IWUSR);
193module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
194 S_IRUGO | S_IWUSR);
195module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
196
197module_init(lowmem_init);
198module_exit(lowmem_exit);
199
200MODULE_LICENSE("GPL");
201
202
