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.
8 * Simple token based thrashing protection, using the algorithm
9 * described in: http://www.cs.wm.edu/~sjiang/token.pdf
11 #include <linux/jiffies.h>
13 #include <linux/sched.h>
14 #include <linux/swap.h>
16 static DEFINE_SPINLOCK(swap_token_lock
);
17 static unsigned long swap_token_timeout
;
18 static unsigned long swap_token_check
;
19 struct mm_struct
* swap_token_mm
= &init_mm
;
21 #define SWAP_TOKEN_CHECK_INTERVAL (HZ * 2)
22 #define SWAP_TOKEN_TIMEOUT 0
24 * Currently disabled; Needs further code to work at HZ * 300.
26 unsigned long swap_token_default_timeout
= SWAP_TOKEN_TIMEOUT
;
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
33 #define SWAP_TOKEN_ENOUGH_RSS 1
34 #define SWAP_TOKEN_TIMED_OUT 2
35 static int should_release_swap_token(struct mm_struct
*mm
)
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;
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.
52 void grab_swap_token(void)
57 /* We have the token. Let others know we still need it. */
58 if (has_swap_token(current
->mm
)) {
59 current
->mm
->recent_pagein
= 1;
63 if (time_after(jiffies
, swap_token_check
)) {
65 /* Can't get swapout protection if we exceed our RSS limit. */
66 // if (current->mm->rss > current->mm->rlimit_rss)
69 /* ... or if we recently held the token. */
70 if (time_before(jiffies
, current
->mm
->swap_token_time
))
73 if (!spin_trylock(&swap_token_lock
))
76 swap_token_check
= jiffies
+ SWAP_TOKEN_CHECK_INTERVAL
;
79 if ((reason
= should_release_swap_token(mm
))) {
80 unsigned long eligible
= jiffies
;
81 if (reason
== SWAP_TOKEN_TIMED_OUT
) {
82 eligible
+= swap_token_default_timeout
;
84 mm
->swap_token_time
= eligible
;
85 swap_token_timeout
= jiffies
+ swap_token_default_timeout
;
86 swap_token_mm
= current
->mm
;
88 spin_unlock(&swap_token_lock
);
93 /* Called on process exit. */
94 void __put_swap_token(struct mm_struct
*mm
)
96 spin_lock(&swap_token_lock
);
97 if (likely(mm
== swap_token_mm
)) {
98 swap_token_mm
= &init_mm
;
99 swap_token_check
= jiffies
;
101 spin_unlock(&swap_token_lock
);