projects / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 1da177e4 LT |
1 | /* |
| 2 | * mm/thrash.c | |
| 3 | * | |
| 4 | * Copyright (C) 2004, Red Hat, Inc. | |
| 5 | * Copyright (C) 2004, Rik van Riel <[email protected]> | |
| 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 | #include <linux/jiffies.h> | |
| 12 | #include <linux/mm.h> | |
| 13 | #include <linux/sched.h> | |
| 14 | #include <linux/swap.h> | |
| 15 | ||
| 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; | |
| 20 | ||
| 21 | #define SWAP_TOKEN_CHECK_INTERVAL (HZ * 2) | |
| fcdae29a | 22 | #define SWAP_TOKEN_TIMEOUT (300 * HZ) |
| 1da177e4 LT |
23 | /* |
| 24 | * Currently disabled; Needs further code to work at HZ * 300. | |
| 25 | */ | |
| 26 | unsigned 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 | |
| 35 | static 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 | ||
| 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 | */ | |
| 52 | void grab_swap_token(void) | |
| 53 | { | |
| 54 | struct mm_struct *mm; | |
| 55 | int reason; | |
| 56 | ||
| 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; | |
| f7b7fd8f RR |
60 | if (unlikely(!swap_token_default_timeout)) |
| 61 | disable_swap_token(); | |
| 1da177e4 LT |
62 | return; |
| 63 | } | |
| 64 | ||
| 65 | if (time_after(jiffies, swap_token_check)) { | |
| 66 | ||
| f7b7fd8f RR |
67 | if (!swap_token_default_timeout) { |
| 68 | swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL; | |
| 69 | return; | |
| 70 | } | |
| 1da177e4 LT |
71 | |
| 72 | /* ... or if we recently held the token. */ | |
| 73 | if (time_before(jiffies, current->mm->swap_token_time)) | |
| 74 | return; | |
| 75 | ||
| 76 | if (!spin_trylock(&swap_token_lock)) | |
| 77 | return; | |
| 78 | ||
| 79 | swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL; | |
| 80 | ||
| 81 | mm = swap_token_mm; | |
| 82 | if ((reason = should_release_swap_token(mm))) { | |
| 83 | unsigned long eligible = jiffies; | |
| 84 | if (reason == SWAP_TOKEN_TIMED_OUT) { | |
| 85 | eligible += swap_token_default_timeout; | |
| 86 | } | |
| 87 | mm->swap_token_time = eligible; | |
| 88 | swap_token_timeout = jiffies + swap_token_default_timeout; | |
| 89 | swap_token_mm = current->mm; | |
| 90 | } | |
| 91 | spin_unlock(&swap_token_lock); | |
| 92 | } | |
| 93 | return; | |
| 94 | } | |
| 95 | ||
| 96 | /* Called on process exit. */ | |
| 97 | void __put_swap_token(struct mm_struct *mm) | |
| 98 | { | |
| 99 | spin_lock(&swap_token_lock); | |
| 100 | if (likely(mm == swap_token_mm)) { | |
| f7b7fd8f | 101 | mm->swap_token_time = jiffies + SWAP_TOKEN_CHECK_INTERVAL; |
| 1da177e4 LT |
102 | swap_token_mm = &init_mm; |
| 103 | swap_token_check = jiffies; | |
| 104 | } | |
| 105 | spin_unlock(&swap_token_lock); | |
| 106 | } |