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Commit ae54abed authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
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cfq-iosched: split seeky coop queues after one slice 



Currently we split seeky coop queues after 1s, which is too big. Below patch
marks seeky coop queue split_coop flag after one slice. After that, if new
requests come in, the queues will be splitted. Patch is suggested by Corrado.

Signed-off-by: default avatarShaohua Li <shaohua.li@intel.com>
Reviewed-by: default avatarCorrado Zoccolo <czoccolo@gmail.com>
Acked-by: default avatarJeff Moyer <jmoyer@redhat.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent fc76be43

block/cfq-iosched.c

+16 −33
Original line number Diff line number Diff line
@@ -42,16 +42,13 @@ static const int cfq_hist_divisor = 4; 
 */

#define CFQ_MIN_TT		(2)



/*

 * Allow merged cfqqs to perform this amount of seeky I/O before

 * deciding to break the queues up again.

 */

#define CFQQ_COOP_TOUT		(HZ)



#define CFQ_SLICE_SCALE		(5)

#define CFQ_HW_QUEUE_MIN	(5)

#define CFQ_SERVICE_SHIFT       12



#define CFQQ_SEEK_THR		8 * 1024

#define CFQQ_SEEKY(cfqq)	((cfqq)->seek_mean > CFQQ_SEEK_THR)



#define RQ_CIC(rq)		\

	((struct cfq_io_context *) (rq)->elevator_private)

#define RQ_CFQQ(rq)		(struct cfq_queue *) ((rq)->elevator_private2)
@@ -137,7 +134,6 @@ struct cfq_queue { 
	u64 seek_total;

	sector_t seek_mean;

	sector_t last_request_pos;

	unsigned long seeky_start;



	pid_t pid;
@@ -314,6 +310,7 @@ enum cfqq_state_flags { 
	CFQ_CFQQ_FLAG_slice_new,	/* no requests dispatched in slice */

	CFQ_CFQQ_FLAG_sync,		/* synchronous queue */

	CFQ_CFQQ_FLAG_coop,		/* cfqq is shared */

	CFQ_CFQQ_FLAG_split_coop,	/* shared cfqq will be splitted */

	CFQ_CFQQ_FLAG_deep,		/* sync cfqq experienced large depth */

	CFQ_CFQQ_FLAG_wait_busy,	/* Waiting for next request */

};
@@ -342,6 +339,7 @@ CFQ_CFQQ_FNS(prio_changed); 
CFQ_CFQQ_FNS(slice_new);

CFQ_CFQQ_FNS(sync);

CFQ_CFQQ_FNS(coop);

CFQ_CFQQ_FNS(split_coop);

CFQ_CFQQ_FNS(deep);

CFQ_CFQQ_FNS(wait_busy);

#undef CFQ_CFQQ_FNS
@@ -1565,6 +1563,15 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	cfq_clear_cfqq_wait_request(cfqq);

	cfq_clear_cfqq_wait_busy(cfqq);



	/*

	 * If this cfqq is shared between multiple processes, check to

	 * make sure that those processes are still issuing I/Os within

	 * the mean seek distance.  If not, it may be time to break the

	 * queues apart again.

	 */

	if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))

		cfq_mark_cfqq_split_coop(cfqq);



	/*

	 * store what was left of this slice, if the queue idled/timed out

	 */
@@ -1663,9 +1670,6 @@ static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd, 
		return cfqd->last_position - blk_rq_pos(rq);

}



#define CFQQ_SEEK_THR		8 * 1024

#define CFQQ_SEEKY(cfqq)	((cfqq)->seek_mean > CFQQ_SEEK_THR)



static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,

			       struct request *rq, bool for_preempt)

{
@@ -3000,19 +3004,6 @@ cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	total = cfqq->seek_total + (cfqq->seek_samples/2);

	do_div(total, cfqq->seek_samples);

	cfqq->seek_mean = (sector_t)total;



	/*

	 * If this cfqq is shared between multiple processes, check to

	 * make sure that those processes are still issuing I/Os within

	 * the mean seek distance.  If not, it may be time to break the

	 * queues apart again.

	 */

	if (cfq_cfqq_coop(cfqq)) {

		if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start)

			cfqq->seeky_start = jiffies;

		else if (!CFQQ_SEEKY(cfqq))

			cfqq->seeky_start = 0;

	}

}



/*
@@ -3453,14 +3444,6 @@ cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic, 
	return cic_to_cfqq(cic, 1);

}



static int should_split_cfqq(struct cfq_queue *cfqq)

{

	if (cfqq->seeky_start &&

	    time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT))

		return 1;

	return 0;

}



/*

 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this

 * was the last process referring to said cfqq.
@@ -3469,9 +3452,9 @@ static struct cfq_queue * 
split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)

{

	if (cfqq_process_refs(cfqq) == 1) {

		cfqq->seeky_start = 0;

		cfqq->pid = current->pid;

		cfq_clear_cfqq_coop(cfqq);

		cfq_clear_cfqq_split_coop(cfqq);

		return cfqq;

	}
@@ -3510,7 +3493,7 @@ cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) 
		/*

		 * If the queue was seeky for too long, break it apart.

		 */

		if (cfq_cfqq_coop(cfqq) && should_split_cfqq(cfqq)) {

		if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {

			cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");

			cfqq = split_cfqq(cic, cfqq);

			if (!cfqq)