Commit 76280aff authored by Corrado Zoccolo's avatar Corrado Zoccolo Committed by Jens Axboe
Browse files

cfq-iosched: idling on deep seeky sync queues 



Seeky sync queues with large depth can gain unfairly big share of disk
 time, at the expense of other seeky queues. This patch ensures that
 idling will be enabled for queues with I/O depth at least 4, and small
 think time. The decision to enable idling is sticky, until an idle
 window times out without seeing a new request.

The reasoning behind the decision is that, if an application is using
large I/O depth, it is already optimized to make full utilization of
the hardware, and therefore we reserve a slice of exclusive use for it.

Reported-by: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent e4a22919

block/cfq-iosched.c

+12 −1
Original line number Diff line number Diff line
@@ -260,6 +260,7 @@ 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_deep,		/* sync cfqq experienced large depth */

};



#define CFQ_CFQQ_FNS(name)						\
@@ -286,6 +287,7 @@ CFQ_CFQQ_FNS(prio_changed); 
CFQ_CFQQ_FNS(slice_new);

CFQ_CFQQ_FNS(sync);

CFQ_CFQQ_FNS(coop);

CFQ_CFQQ_FNS(deep);

#undef CFQ_CFQQ_FNS



#define cfq_log_cfqq(cfqd, cfqq, fmt, args...)	\
@@ -2350,8 +2352,12 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, 


	enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);



	if (cfqq->queued[0] + cfqq->queued[1] >= 4)

		cfq_mark_cfqq_deep(cfqq);



	if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||

	    (sample_valid(cfqq->seek_samples) && CFQQ_SEEKY(cfqq)))

	    (!cfq_cfqq_deep(cfqq) && sample_valid(cfqq->seek_samples)

	     && CFQQ_SEEKY(cfqq)))

		enable_idle = 0;

	else if (sample_valid(cic->ttime_samples)) {

		if (cic->ttime_mean > cfqd->cfq_slice_idle)
@@ -2849,6 +2855,11 @@ static void cfq_idle_slice_timer(unsigned long data) 
		 */

		if (!RB_EMPTY_ROOT(&cfqq->sort_list))

			goto out_kick;



		/*

		 * Queue depth flag is reset only when the idle didn't succeed

		 */

		cfq_clear_cfqq_deep(cfqq);

	}

expire:

	cfq_slice_expired(cfqd, timed_out);

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