[PATCH] I2C: Separate non-i2c hwmon drivers from i2c-core (8/9)
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / mm / thrash.c
blob11461f7ad8302c499ae43ddc78926848db65d5a8
1 /*
2 * mm/thrash.c
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>
12 #include <linux/mm.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
31 * too long.
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)
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;
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)
54 struct mm_struct *mm;
55 int reason;
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;
60 return;
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)
67 // return;
69 /* ... or if we recently held the token. */
70 if (time_before(jiffies, current->mm->swap_token_time))
71 return;
73 if (!spin_trylock(&swap_token_lock))
74 return;
76 swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
78 mm = swap_token_mm;
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);
90 return;
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);