thrash.c revision 53bb01f593d50188c8d638f89db96f9b6b042bcd 
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.cse.ohio-state.edu/hpcs/WWW/HTML/publications/abs05-1.html
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
30static DEFINE_SPINLOCK(swap_token_lock);
31struct mm_struct *swap_token_mm;
32struct mem_cgroup *swap_token_memcg;
33
34#ifdef CONFIG_CGROUP_MEM_RES_CTLR
35static struct mem_cgroup *swap_token_memcg_from_mm(struct mm_struct *mm)
36{
37	struct mem_cgroup *memcg;
38
39	memcg = try_get_mem_cgroup_from_mm(mm);
40	if (memcg)
41		css_put(mem_cgroup_css(memcg));
42
43	return memcg;
44}
45#else
46static struct mem_cgroup *swap_token_memcg_from_mm(struct mm_struct *mm)
47{
48	return NULL;
49}
50#endif
51
52void grab_swap_token(struct mm_struct *mm)
53{
54	int current_interval;
55	unsigned int old_prio = mm->token_priority;
56	static unsigned int global_faults;
57	static unsigned int last_aging;
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
91update_priority:
92	trace_update_swap_token_priority(mm, old_prio, swap_token_mm);
93
94out:
95	mm->faultstamp = global_faults;
96	mm->last_interval = current_interval;
97	spin_unlock(&swap_token_lock);
98	return;
99
100replace_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. */
110void __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
121static 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
132void 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