| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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.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) |
| 22 | #define SWAP_TOKEN_TIMEOUT 0 |
| 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; |
| 60 | return; |
| 61 | } |
| 62 | |
| 63 | if (time_after(jiffies, swap_token_check)) { |
| 64 | |
| 65 | /* Can't get swapout protection if we exceed our RSS limit. */ |
| 66 | // if (current->mm->rss > current->mm->rlimit_rss) |
| 67 | // return; |
| 68 | |
| 69 | /* ... or if we recently held the token. */ |
| 70 | if (time_before(jiffies, current->mm->swap_token_time)) |
| 71 | return; |
| 72 | |
| 73 | if (!spin_trylock(&swap_token_lock)) |
| 74 | return; |
| 75 | |
| 76 | swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL; |
| 77 | |
| 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; |
| 83 | } |
| 84 | mm->swap_token_time = eligible; |
| 85 | swap_token_timeout = jiffies + swap_token_default_timeout; |
| 86 | swap_token_mm = current->mm; |
| 87 | } |
| 88 | spin_unlock(&swap_token_lock); |
| 89 | } |
| 90 | return; |
| 91 | } |
| 92 | |
| 93 | /* Called on process exit. */ |
| 94 | void __put_swap_token(struct mm_struct *mm) |
| 95 | { |
| 96 | spin_lock(&swap_token_lock); |
| 97 | if (likely(mm == swap_token_mm)) { |
| 98 | swap_token_mm = &init_mm; |
| 99 | swap_token_check = jiffies; |
| 100 | } |
| 101 | spin_unlock(&swap_token_lock); |
| 102 | } |