107 lines
2.7 KiB
C
107 lines
2.7 KiB
C
/*
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* mm/thrash.c
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*
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* Copyright (C) 2004, Red Hat, Inc.
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* Copyright (C) 2004, Rik van Riel <riel@redhat.com>
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* Released under the GPL, see the file COPYING for details.
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*
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* Simple token based thrashing protection, using the algorithm
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* described in: http://www.cs.wm.edu/~sjiang/token.pdf
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*/
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#include <linux/jiffies.h>
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/swap.h>
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static DEFINE_SPINLOCK(swap_token_lock);
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static unsigned long swap_token_timeout;
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static unsigned long swap_token_check;
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struct mm_struct * swap_token_mm = &init_mm;
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#define SWAP_TOKEN_CHECK_INTERVAL (HZ * 2)
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#define SWAP_TOKEN_TIMEOUT (300 * HZ)
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/*
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* Currently disabled; Needs further code to work at HZ * 300.
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*/
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unsigned long swap_token_default_timeout = SWAP_TOKEN_TIMEOUT;
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/*
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* Take the token away if the process had no page faults
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* in the last interval, or if it has held the token for
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* too long.
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*/
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#define SWAP_TOKEN_ENOUGH_RSS 1
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#define SWAP_TOKEN_TIMED_OUT 2
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static int should_release_swap_token(struct mm_struct *mm)
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{
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int ret = 0;
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if (!mm->recent_pagein)
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ret = SWAP_TOKEN_ENOUGH_RSS;
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else if (time_after(jiffies, swap_token_timeout))
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ret = SWAP_TOKEN_TIMED_OUT;
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mm->recent_pagein = 0;
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return ret;
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}
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/*
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* Try to grab the swapout protection token. We only try to
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* grab it once every TOKEN_CHECK_INTERVAL, both to prevent
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* SMP lock contention and to check that the process that held
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* the token before is no longer thrashing.
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*/
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void grab_swap_token(void)
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{
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struct mm_struct *mm;
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int reason;
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/* We have the token. Let others know we still need it. */
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if (has_swap_token(current->mm)) {
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current->mm->recent_pagein = 1;
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if (unlikely(!swap_token_default_timeout))
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disable_swap_token();
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return;
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}
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if (time_after(jiffies, swap_token_check)) {
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if (!swap_token_default_timeout) {
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swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
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return;
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}
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/* ... or if we recently held the token. */
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if (time_before(jiffies, current->mm->swap_token_time))
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return;
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if (!spin_trylock(&swap_token_lock))
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return;
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swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
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mm = swap_token_mm;
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if ((reason = should_release_swap_token(mm))) {
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unsigned long eligible = jiffies;
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if (reason == SWAP_TOKEN_TIMED_OUT) {
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eligible += swap_token_default_timeout;
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}
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mm->swap_token_time = eligible;
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swap_token_timeout = jiffies + swap_token_default_timeout;
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swap_token_mm = current->mm;
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}
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spin_unlock(&swap_token_lock);
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}
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return;
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}
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/* Called on process exit. */
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void __put_swap_token(struct mm_struct *mm)
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{
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spin_lock(&swap_token_lock);
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if (likely(mm == swap_token_mm)) {
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mm->swap_token_time = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
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swap_token_mm = &init_mm;
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swap_token_check = jiffies;
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}
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spin_unlock(&swap_token_lock);
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}
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