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-rw-r--r--mm/thrash.c116
1 files changed, 45 insertions, 71 deletions
diff --git a/mm/thrash.c b/mm/thrash.c
index f4c560b4a2b7..19e428ca8b03 100644
--- a/mm/thrash.c
+++ b/mm/thrash.c
@@ -7,100 +7,74 @@
7 * 7 *
8 * Simple token based thrashing protection, using the algorithm 8 * Simple token based thrashing protection, using the algorithm
9 * described in: http://www.cs.wm.edu/~sjiang/token.pdf 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.
10 */ 18 */
19
11#include <linux/jiffies.h> 20#include <linux/jiffies.h>
12#include <linux/mm.h> 21#include <linux/mm.h>
13#include <linux/sched.h> 22#include <linux/sched.h>
14#include <linux/swap.h> 23#include <linux/swap.h>
15 24
16static DEFINE_SPINLOCK(swap_token_lock); 25static DEFINE_SPINLOCK(swap_token_lock);
17static unsigned long swap_token_timeout; 26struct mm_struct *swap_token_mm;
18static unsigned long swap_token_check; 27unsigned int global_faults;
19struct mm_struct * swap_token_mm = &init_mm;
20
21#define SWAP_TOKEN_CHECK_INTERVAL (HZ * 2)
22#define SWAP_TOKEN_TIMEOUT (300 * HZ)
23/*
24 * Currently disabled; Needs further code to work at HZ * 300.
25 */
26unsigned long swap_token_default_timeout = SWAP_TOKEN_TIMEOUT;
27
28/*
29 * Take the token away if the process had no page faults
30 * in the last interval, or if it has held the token for
31 * too long.
32 */
33#define SWAP_TOKEN_ENOUGH_RSS 1
34#define SWAP_TOKEN_TIMED_OUT 2
35static int should_release_swap_token(struct mm_struct *mm)
36{
37 int ret = 0;
38 if (!mm->recent_pagein)
39 ret = SWAP_TOKEN_ENOUGH_RSS;
40 else if (time_after(jiffies, swap_token_timeout))
41 ret = SWAP_TOKEN_TIMED_OUT;
42 mm->recent_pagein = 0;
43 return ret;
44}
45 28
46/*
47 * Try to grab the swapout protection token. We only try to
48 * grab it once every TOKEN_CHECK_INTERVAL, both to prevent
49 * SMP lock contention and to check that the process that held
50 * the token before is no longer thrashing.
51 */
52void grab_swap_token(void) 29void grab_swap_token(void)
53{ 30{
54 struct mm_struct *mm; 31 int current_interval;
55 int reason;
56 32
57 /* We have the token. Let others know we still need it. */ 33 global_faults++;
58 if (has_swap_token(current->mm)) {
59 current->mm->recent_pagein = 1;
60 if (unlikely(!swap_token_default_timeout))
61 disable_swap_token();
62 return;
63 }
64
65 if (time_after(jiffies, swap_token_check)) {
66 34
67 if (!swap_token_default_timeout) { 35 current_interval = global_faults - current->mm->faultstamp;
68 swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
69 return;
70 }
71
72 /* ... or if we recently held the token. */
73 if (time_before(jiffies, current->mm->swap_token_time))
74 return;
75 36
76 if (!spin_trylock(&swap_token_lock)) 37 if (!spin_trylock(&swap_token_lock))
77 return; 38 return;
78 39
79 swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL; 40 /* First come first served */
41 if (swap_token_mm == NULL) {
42 current->mm->token_priority = current->mm->token_priority + 2;
43 swap_token_mm = current->mm;
44 goto out;
45 }
80 46
81 mm = swap_token_mm; 47 if (current->mm != swap_token_mm) {
82 if ((reason = should_release_swap_token(mm))) { 48 if (current_interval < current->mm->last_interval)
83 unsigned long eligible = jiffies; 49 current->mm->token_priority++;
84 if (reason == SWAP_TOKEN_TIMED_OUT) { 50 else {
85 eligible += swap_token_default_timeout; 51 current->mm->token_priority--;
86 } 52 if (unlikely(current->mm->token_priority < 0))
87 mm->swap_token_time = eligible; 53 current->mm->token_priority = 0;
88 swap_token_timeout = jiffies + swap_token_default_timeout; 54 }
55 /* Check if we deserve the token */
56 if (current->mm->token_priority >
57 swap_token_mm->token_priority) {
58 current->mm->token_priority += 2;
89 swap_token_mm = current->mm; 59 swap_token_mm = current->mm;
90 } 60 }
91 spin_unlock(&swap_token_lock); 61 } else {
62 /* Token holder came in again! */
63 current->mm->token_priority += 2;
92 } 64 }
93 return; 65
66out:
67 current->mm->faultstamp = global_faults;
68 current->mm->last_interval = current_interval;
69 spin_unlock(&swap_token_lock);
70return;
94} 71}
95 72
96/* Called on process exit. */ 73/* Called on process exit. */
97void __put_swap_token(struct mm_struct *mm) 74void __put_swap_token(struct mm_struct *mm)
98{ 75{
99 spin_lock(&swap_token_lock); 76 spin_lock(&swap_token_lock);
100 if (likely(mm == swap_token_mm)) { 77 if (likely(mm == swap_token_mm))
101 mm->swap_token_time = jiffies + SWAP_TOKEN_CHECK_INTERVAL; 78 swap_token_mm = NULL;
102 swap_token_mm = &init_mm;
103 swap_token_check = jiffies;
104 }
105 spin_unlock(&swap_token_lock); 79 spin_unlock(&swap_token_lock);
106} 80}
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