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Commit b53d1ed7 authored by Jens Axboe's avatar Jens Axboe
Browse files

Revert "cfq: Remove special treatment for metadata rqs." 



We have a kernel build regression since 3.1-rc1, which is about 10%
regression. The kernel source is in an ext3 filesystem.
Alex Shi bisect it to commit:
commit a07405b7
Author: Justin TerAvest <teravest@google.com>
Date:   Sun Jul 10 22:09:19 2011 +0200

    cfq: Remove special treatment for metadata rqs.

Apparently this is caused by lack metadata preemption, where ext3/ext4
do use READ_META. I didn't see a way to fix the issue, so suggest
reverting the patch.

This reverts commit a07405b7.

Reported-by: default avatarAlex <Shi&lt;alex.shi@intel.com>
Reported-by: default avatarShaohua <Li&lt;shaohua.li@intel.com>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 4853abaa

block/cfq-iosched.c

+18 −0
Original line number Diff line number Diff line
@@ -130,6 +130,8 @@ struct cfq_queue { 
	unsigned long slice_end;

	long slice_resid;



	/* pending metadata requests */

	int meta_pending;

	/* number of requests that are on the dispatch list or inside driver */

	int dispatched;
@@ -682,6 +684,9 @@ cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, 
	if (rq_is_sync(rq1) != rq_is_sync(rq2))

		return rq_is_sync(rq1) ? rq1 : rq2;



	if ((rq1->cmd_flags ^ rq2->cmd_flags) & REQ_META)

		return rq1->cmd_flags & REQ_META ? rq1 : rq2;



	s1 = blk_rq_pos(rq1);

	s2 = blk_rq_pos(rq2);
@@ -1607,6 +1612,10 @@ static void cfq_remove_request(struct request *rq) 
	cfqq->cfqd->rq_queued--;

	cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,

					rq_data_dir(rq), rq_is_sync(rq));

	if (rq->cmd_flags & REQ_META) {

		WARN_ON(!cfqq->meta_pending);

		cfqq->meta_pending--;

	}

}



static int cfq_merge(struct request_queue *q, struct request **req,
@@ -3359,6 +3368,13 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 
	    RB_EMPTY_ROOT(&cfqq->sort_list))

		return true;



	/*

	 * So both queues are sync. Let the new request get disk time if

	 * it's a metadata request and the current queue is doing regular IO.

	 */

	if ((rq->cmd_flags & REQ_META) && !cfqq->meta_pending)

		return true;



	/*

	 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.

	 */
@@ -3423,6 +3439,8 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	struct cfq_io_context *cic = RQ_CIC(rq);



	cfqd->rq_queued++;

	if (rq->cmd_flags & REQ_META)

		cfqq->meta_pending++;



	cfq_update_io_thinktime(cfqd, cfqq, cic);

	cfq_update_io_seektime(cfqd, cfqq, rq);