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1 | /* |
2 | * mm/thrash.c |
3 | * |
4 | * Copyright (C) 2004, Red Hat, Inc. |
5 | * Copyright (C) 2004, Rik van Riel <riel@redhat.com> |
6 | * Released under the GPL, see the file COPYING for details. |
7 | * |
8 | * Simple token based thrashing protection, using the algorithm |
9 | * described in: http://www.cs.wm.edu/~sjiang/token.pdf |
10 | * |
11 | * Sep 2006, Ashwin Chaugule <ashwin.chaugule@celunite.com> |
12 | * Improved algorithm to pass token: |
13 | * Each task has a priority which is incremented if it contended |
14 | * for the token in an interval less than its previous attempt. |
15 | * If the token is acquired, that task's priority is boosted to prevent |
16 | * the token from bouncing around too often and to let the task make |
17 | * some progress in its execution. |
18 | */ |
19 | |
20 | #include <linux/jiffies.h> |
21 | #include <linux/mm.h> |
22 | #include <linux/sched.h> |
23 | #include <linux/swap.h> |
24 | #include <linux/memcontrol.h> |
25 | |
26 | #include <trace/events/vmscan.h> |
27 | |
28 | #define TOKEN_AGING_INTERVAL (0xFF) |
29 | |
30 | static DEFINE_SPINLOCK(swap_token_lock); |
31 | struct mm_struct *swap_token_mm; |
32 | struct mem_cgroup *swap_token_memcg; |
33 | static unsigned int global_faults; |
34 | static unsigned int last_aging; |
35 | |
36 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
37 | static struct mem_cgroup *swap_token_memcg_from_mm(struct mm_struct *mm) |
38 | { |
39 | struct mem_cgroup *memcg; |
40 | |
41 | memcg = try_get_mem_cgroup_from_mm(mm); |
42 | if (memcg) |
43 | css_put(mem_cgroup_css(memcg)); |
44 | |
45 | return memcg; |
46 | } |
47 | #else |
48 | static struct mem_cgroup *swap_token_memcg_from_mm(struct mm_struct *mm) |
49 | { |
50 | return NULL; |
51 | } |
52 | #endif |
53 | |
54 | void grab_swap_token(struct mm_struct *mm) |
55 | { |
56 | int current_interval; |
57 | unsigned int old_prio = mm->token_priority; |
58 | |
59 | global_faults++; |
60 | |
61 | current_interval = global_faults - mm->faultstamp; |
62 | |
63 | if (!spin_trylock(&swap_token_lock)) |
64 | return; |
65 | |
66 | /* First come first served */ |
67 | if (!swap_token_mm) |
68 | goto replace_token; |
69 | |
70 | if ((global_faults - last_aging) > TOKEN_AGING_INTERVAL) { |
71 | swap_token_mm->token_priority /= 2; |
72 | last_aging = global_faults; |
73 | } |
74 | |
75 | if (mm == swap_token_mm) { |
76 | mm->token_priority += 2; |
77 | goto update_priority; |
78 | } |
79 | |
80 | if (current_interval < mm->last_interval) |
81 | mm->token_priority++; |
82 | else { |
83 | if (likely(mm->token_priority > 0)) |
84 | mm->token_priority--; |
85 | } |
86 | |
87 | /* Check if we deserve the token */ |
88 | if (mm->token_priority > swap_token_mm->token_priority) |
89 | goto replace_token; |
90 | |
91 | update_priority: |
92 | trace_update_swap_token_priority(mm, old_prio, swap_token_mm); |
93 | |
94 | out: |
95 | mm->faultstamp = global_faults; |
96 | mm->last_interval = current_interval; |
97 | spin_unlock(&swap_token_lock); |
98 | return; |
99 | |
100 | replace_token: |
101 | mm->token_priority += 2; |
102 | trace_replace_swap_token(swap_token_mm, mm); |
103 | swap_token_mm = mm; |
104 | swap_token_memcg = swap_token_memcg_from_mm(mm); |
105 | last_aging = global_faults; |
106 | goto out; |
107 | } |
108 | |
109 | /* Called on process exit. */ |
110 | void __put_swap_token(struct mm_struct *mm) |
111 | { |
112 | spin_lock(&swap_token_lock); |
113 | if (likely(mm == swap_token_mm)) { |
114 | trace_put_swap_token(swap_token_mm); |
115 | swap_token_mm = NULL; |
116 | swap_token_memcg = NULL; |
117 | } |
118 | spin_unlock(&swap_token_lock); |
119 | } |
120 | |
121 | static bool match_memcg(struct mem_cgroup *a, struct mem_cgroup *b) |
122 | { |
123 | if (!a) |
124 | return true; |
125 | if (!b) |
126 | return true; |
127 | if (a == b) |
128 | return true; |
129 | return false; |
130 | } |
131 | |
132 | void disable_swap_token(struct mem_cgroup *memcg) |
133 | { |
134 | /* memcg reclaim don't disable unrelated mm token. */ |
135 | if (match_memcg(memcg, swap_token_memcg)) { |
136 | spin_lock(&swap_token_lock); |
137 | if (match_memcg(memcg, swap_token_memcg)) { |
138 | trace_disable_swap_token(swap_token_mm); |
139 | swap_token_mm = NULL; |
140 | swap_token_memcg = NULL; |
141 | } |
142 | spin_unlock(&swap_token_lock); |
143 | } |
144 | } |
145 |
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