Commit 089716aa authored by Dave Chinner's avatar Dave Chinner
Browse files

xfs: Sort delayed write buffers before dispatch 



Currently when the xfsbufd writes delayed write buffers, it pushes
them to disk in the order they come off the delayed write list. If
there are lots of buffers ѕpread widely over the disk, this results
in overwhelming the elevator sort queues in the block layer and we
end up losing the posibility of merging adjacent buffers to minimise
the number of IOs.

Use the new generic list_sort function to sort the delwri dispatch
queue before issue to ensure that the buffers are pushed in the most
friendly order possible to the lower layers.

Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
parent d808f617

fs/xfs/linux-2.6/xfs_buf.c

+60 −27
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ 
#include <linux/migrate.h>

#include <linux/backing-dev.h>

#include <linux/freezer.h>

#include <linux/list_sort.h>



#include "xfs_sb.h"

#include "xfs_inum.h"
@@ -1877,14 +1878,42 @@ xfs_buf_delwri_split( 


}



/*

 * Compare function is more complex than it needs to be because

 * the return value is only 32 bits and we are doing comparisons

 * on 64 bit values

 */

static int

xfs_buf_cmp(

	void		*priv,

	struct list_head *a,

	struct list_head *b)

{

	struct xfs_buf	*ap = container_of(a, struct xfs_buf, b_list);

	struct xfs_buf	*bp = container_of(b, struct xfs_buf, b_list);

	xfs_daddr_t		diff;



	diff = ap->b_bn - bp->b_bn;

	if (diff < 0)

		return -1;

	if (diff > 0)

		return 1;

	return 0;

}



void

xfs_buf_delwri_sort(

	xfs_buftarg_t	*target,

	struct list_head *list)

{

	list_sort(NULL, list, xfs_buf_cmp);

}



STATIC int

xfsbufd(

	void		*data)

{

	struct list_head tmp;

	xfs_buftarg_t   *target = (xfs_buftarg_t *)data;

	int		count;

	xfs_buf_t	*bp;



	current->flags |= PF_MEMALLOC;
@@ -1893,6 +1922,8 @@ xfsbufd( 
	do {

		long	age = xfs_buf_age_centisecs * msecs_to_jiffies(10);

		long	tout = xfs_buf_timer_centisecs * msecs_to_jiffies(10);

		int	count = 0;

		struct list_head tmp;



		if (unlikely(freezing(current))) {

			set_bit(XBT_FORCE_SLEEP, &target->bt_flags);
@@ -1907,11 +1938,10 @@ xfsbufd( 
		schedule_timeout_interruptible(tout);



		xfs_buf_delwri_split(target, &tmp, age);

		count = 0;

		list_sort(NULL, &tmp, xfs_buf_cmp);

		while (!list_empty(&tmp)) {

			bp = list_entry(tmp.next, xfs_buf_t, b_list);

			ASSERT(target == bp->b_target);



			struct xfs_buf *bp;

			bp = list_first_entry(&tmp, struct xfs_buf, b_list);

			list_del_init(&bp->b_list);

			xfs_buf_iostrategy(bp);

			count++;
@@ -1937,43 +1967,46 @@ xfs_flush_buftarg( 
	xfs_buftarg_t	*target,

	int		wait)

{

	struct list_head tmp;

	xfs_buf_t	*bp, *n;

	xfs_buf_t	*bp;

	int		pincount = 0;

	LIST_HEAD(tmp_list);

	LIST_HEAD(wait_list);



	xfs_buf_runall_queues(xfsconvertd_workqueue);

	xfs_buf_runall_queues(xfsdatad_workqueue);

	xfs_buf_runall_queues(xfslogd_workqueue);



	set_bit(XBT_FORCE_FLUSH, &target->bt_flags);

	pincount = xfs_buf_delwri_split(target, &tmp, 0);

	pincount = xfs_buf_delwri_split(target, &tmp_list, 0);



	/*

	 * Dropped the delayed write list lock, now walk the temporary list

	 * Dropped the delayed write list lock, now walk the temporary list.

	 * All I/O is issued async and then if we need to wait for completion

	 * we do that after issuing all the IO.

	 */

	list_for_each_entry_safe(bp, n, &tmp, b_list) {

	list_sort(NULL, &tmp_list, xfs_buf_cmp);

	while (!list_empty(&tmp_list)) {

		bp = list_first_entry(&tmp_list, struct xfs_buf, b_list);

		ASSERT(target == bp->b_target);

		if (wait)

			bp->b_flags &= ~XBF_ASYNC;

		else

		list_del_init(&bp->b_list);



		if (wait) {

			bp->b_flags &= ~XBF_ASYNC;

			list_add(&bp->b_list, &wait_list);

		}

		xfs_buf_iostrategy(bp);

	}



	if (wait)

	if (wait) {

		/* Expedite and wait for IO to complete. */

		blk_run_address_space(target->bt_mapping);



	/*

	 * Remaining list items must be flushed before returning

	 */

	while (!list_empty(&tmp)) {

		bp = list_entry(tmp.next, xfs_buf_t, b_list);

		while (!list_empty(&wait_list)) {

			bp = list_first_entry(&wait_list, struct xfs_buf, b_list);



			list_del_init(&bp->b_list);

			xfs_iowait(bp);

			xfs_buf_relse(bp);

		}

	}



	return pincount;

}

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