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

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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 a07405b780
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 a07405b780.

Reported-by: Alex Shi<alex.shi@intel.com>
Reported-by: Shaohua Li<shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Jens Axboe 2011-08-19 08:34:48 +02:00
parent 4853abaae7
commit b53d1ed734
1 changed files with 18 additions and 0 deletions
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18
block/cfq-iosched.c
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@ -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);