[linux-2.6-block.git] / mm / thrash.c

/*
 * 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	(300 * HZ)
/*
 * 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;
		if (unlikely(!swap_token_default_timeout))
			disable_swap_token();
		return;
	}

	if (time_after(jiffies, swap_token_check)) {

		if (!swap_token_default_timeout) {
			swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
			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)) {
		mm->swap_token_time = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
		swap_token_mm = &init_mm;
		swap_token_check = jiffies;
	}
	spin_unlock(&swap_token_lock);
}
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 <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)
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))
f7b7fd8f RR	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	}