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| author | Jens Axboe <jens.axboe@oracle.com> | 2007-04-20 08:55:52 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-04-20 22:56:29 -0700 |
| commit | a993800655ee516b6f6a6fc4c2ee13fedfb0590b (patch) | |
| tree | 023b362b4b30bddf2232ade83d162a84ac88f74b | |
| parent | 46fcc86dd71d70211e965102fb69414c90381880 (diff) | |
| download | linux-a993800655ee516b6f6a6fc4c2ee13fedfb0590b.tar.gz linux-a993800655ee516b6f6a6fc4c2ee13fedfb0590b.tar.bz2 linux-a993800655ee516b6f6a6fc4c2ee13fedfb0590b.zip | |
cfq-iosched: fix sequential write regression
We have a 10-15% performance regression for sequential writes on TCQ/NCQ
enabled drives in 2.6.21-rcX after the CFQ update went in. It has been
reported by Valerie Clement <valerie.clement@bull.net> and the Intel
testing folks. The regression is because of CFQ's now more aggressive
queue control, limiting the depth available to the device.
This patches fixes that regression by allowing a greater depth when only
one queue is busy. It has been tested to not impact sync-vs-async
workloads too much - we still do a lot better than 2.6.20.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | block/cfq-iosched.c | 34 |
1 files changed, 19 insertions, 15 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index b6491c020f26..9e3797167c81 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -986,9 +986,9 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq, * expire an async queue immediately if it has used up its slice. idle * queue always expire after 1 dispatch round. */ - if ((!cfq_cfqq_sync(cfqq) && + if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) && cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) || - cfq_class_idle(cfqq)) { + cfq_class_idle(cfqq))) { cfqq->slice_end = jiffies + 1; cfq_slice_expired(cfqd, 0, 0); } @@ -1051,19 +1051,21 @@ cfq_dispatch_requests(request_queue_t *q, int force) while ((cfqq = cfq_select_queue(cfqd)) != NULL) { int max_dispatch; - /* - * Don't repeat dispatch from the previous queue. - */ - if (prev_cfqq == cfqq) - break; + if (cfqd->busy_queues > 1) { + /* + * Don't repeat dispatch from the previous queue. + */ + if (prev_cfqq == cfqq) + break; - /* - * So we have dispatched before in this round, if the - * next queue has idling enabled (must be sync), don't - * allow it service until the previous have continued. - */ - if (cfqd->rq_in_driver && cfq_cfqq_idle_window(cfqq)) - break; + /* + * So we have dispatched before in this round, if the + * next queue has idling enabled (must be sync), don't + * allow it service until the previous have continued. + */ + if (cfqd->rq_in_driver && cfq_cfqq_idle_window(cfqq)) + break; + } cfq_clear_cfqq_must_dispatch(cfqq); cfq_clear_cfqq_wait_request(cfqq); @@ -1370,7 +1372,9 @@ retry: atomic_set(&cfqq->ref, 0); cfqq->cfqd = cfqd; - cfq_mark_cfqq_idle_window(cfqq); + if (key != CFQ_KEY_ASYNC) + cfq_mark_cfqq_idle_window(cfqq); + cfq_mark_cfqq_prio_changed(cfqq); cfq_mark_cfqq_queue_new(cfqq); cfq_init_prio_data(cfqq); |