/* * mm/thrash.c * * Copyright (C) 2004, Red Hat, Inc. * Copyright (C) 2004, Rik van Riel <riel@redhat.com> * Released under the GPL, see the file COPYING for details. * * Simple token based thrashing protection, using the algorithm * described in: http://www.cs.wm.edu/~sjiang/token.pdf */ #include <linux/jiffies.h> #include <linux/mm.h> #include <linux/sched.h> #include <linux/swap.h> static DEFINE_SPINLOCK(swap_token_lock); static unsigned long swap_token_timeout; static unsigned long swap_token_check; struct mm_struct * swap_token_mm = &init_mm; #define SWAP_TOKEN_CHECK_INTERVAL (HZ * 2) #define SWAP_TOKEN_TIMEOUT 0 /* * Currently disabled; Needs further code to work at HZ * 300. */ unsigned long swap_token_default_timeout = SWAP_TOKEN_TIMEOUT; /* * Take the token away if the process had no page faults * in the last interval, or if it has held the token for * too long. */ #define SWAP_TOKEN_ENOUGH_RSS 1 #define SWAP_TOKEN_TIMED_OUT 2 static int should_release_swap_token(struct mm_struct *mm) { int ret = 0; if (!mm->recent_pagein) ret = SWAP_TOKEN_ENOUGH_RSS; else if (time_after(jiffies, swap_token_timeout)) ret = SWAP_TOKEN_TIMED_OUT; mm->recent_pagein = 0; return ret; } /* * Try to grab the swapout protection token. We only try to * grab it once every TOKEN_CHECK_INTERVAL, both to prevent * SMP lock contention and to check that the process that held * the token before is no longer thrashing. */ void grab_swap_token(void) { struct mm_struct *mm; int reason; /* We have the token. Let others know we still need it. */ if (has_swap_token(current->mm)) { current->mm->recent_pagein = 1; return; } if (time_after(jiffies, swap_token_check)) { /* Can't get swapout protection if we exceed our RSS limit. */ // if (current->mm->rss > current->mm->rlimit_rss) // return; /* ... or if we recently held the token. */ if (time_before(jiffies, current->mm->swap_token_time)) return; if (!spin_trylock(&swap_token_lock)) return; swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL; mm = swap_token_mm; if ((reason = should_release_swap_token(mm))) { unsigned long eligible = jiffies; if (reason == SWAP_TOKEN_TIMED_OUT) { eligible += swap_token_default_timeout; } mm->swap_token_time = eligible; swap_token_timeout = jiffies + swap_token_default_timeout; swap_token_mm = current->mm; } spin_unlock(&swap_token_lock); } return; } /* Called on process exit. */ void __put_swap_token(struct mm_struct *mm) { spin_lock(&swap_token_lock); if (likely(mm == swap_token_mm)) { swap_token_mm = &init_mm; swap_token_check = jiffies; } spin_unlock(&swap_token_lock); }