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Commit 782f5697 authored by Jens Axboe's avatar Jens Axboe
Browse files

blk-wbt: throttle discards like background writes 



Throttle discards like we would any background write. Discards should
be background activity, so if they are impacting foreground IO, then
we will throttle them down.

Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 8bea6090

block/blk-stat.h

+3 −3
Original line number Diff line number Diff line
@@ -10,11 +10,11 @@ 


/*

 * from upper:

 * 3 bits: reserved for other usage

 * 4 bits: reserved for other usage

 * 12 bits: size

 * 49 bits: time

 * 48 bits: time

 */

#define BLK_STAT_RES_BITS	3

#define BLK_STAT_RES_BITS	4

#define BLK_STAT_SIZE_BITS	12

#define BLK_STAT_RES_SHIFT	(64 - BLK_STAT_RES_BITS)

#define BLK_STAT_SIZE_SHIFT	(BLK_STAT_RES_SHIFT - BLK_STAT_SIZE_BITS)

block/blk-wbt.c

+26 −17
Original line number Diff line number Diff line
@@ -106,6 +106,8 @@ static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb, 
{

	if (wb_acct & WBT_KSWAPD)

		return &rwb->rq_wait[WBT_RWQ_KSWAPD];

	else if (wb_acct & WBT_DISCARD)

		return &rwb->rq_wait[WBT_RWQ_DISCARD];



	return &rwb->rq_wait[WBT_RWQ_BG];

}
@@ -143,10 +145,13 @@ void __wbt_done(struct rq_wb *rwb, enum wbt_flags wb_acct) 
	}



	/*

	 * If the device does write back caching, drop further down

	 * before we wake people up.

	 * For discards, our limit is always the background. For writes, if

	 * the device does write back caching, drop further down before we

	 * wake people up.

	 */

	if (rwb->wc && !wb_recent_wait(rwb))

	if (wb_acct & WBT_DISCARD)

		limit = rwb->wb_background;

	else if (rwb->wc && !wb_recent_wait(rwb))

		limit = 0;

	else

		limit = rwb->wb_normal;
@@ -483,6 +488,9 @@ static inline unsigned int get_limit(struct rq_wb *rwb, unsigned long rw) 
{

	unsigned int limit;



	if ((rw & REQ_OP_MASK) == REQ_OP_DISCARD)

		return rwb->wb_background;



	/*

	 * At this point we know it's a buffered write. If this is

	 * kswapd trying to free memory, or REQ_SYNC is set, then
@@ -564,21 +572,20 @@ static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct, 


static inline bool wbt_should_throttle(struct rq_wb *rwb, struct bio *bio)

{

	const int op = bio_op(bio);



	/*

	 * If not a WRITE, do nothing

	 */

	if (op != REQ_OP_WRITE)

		return false;



	switch (bio_op(bio)) {

	case REQ_OP_WRITE:

		/*

		 * Don't throttle WRITE_ODIRECT

		 */

	if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) == (REQ_SYNC | REQ_IDLE))

		if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) ==

		    (REQ_SYNC | REQ_IDLE))

			return false;



		/* fallthrough */

	case REQ_OP_DISCARD:

		return true;

	default:

		return false;

	}

}



/*
@@ -605,6 +612,8 @@ enum wbt_flags wbt_wait(struct rq_wb *rwb, struct bio *bio, spinlock_t *lock) 


	if (current_is_kswapd())

		ret |= WBT_KSWAPD;

	if (bio_op(bio) == REQ_OP_DISCARD)

		ret |= WBT_DISCARD;



	__wbt_wait(rwb, ret, bio->bi_opf, lock);

block/blk-wbt.h

+3 −1
Original line number Diff line number Diff line
@@ -14,13 +14,15 @@ enum wbt_flags { 
	WBT_TRACKED		= 1,	/* write, tracked for throttling */

	WBT_READ		= 2,	/* read */

	WBT_KSWAPD		= 4,	/* write, from kswapd */

	WBT_DISCARD		= 8,	/* discard */



	WBT_NR_BITS		= 3,	/* number of bits */

	WBT_NR_BITS		= 4,	/* number of bits */

};



enum {

	WBT_RWQ_BG		= 0,

	WBT_RWQ_KSWAPD,

	WBT_RWQ_DISCARD,

	WBT_NUM_RWQ,

};