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authorJens Axboe <jens.axboe@oracle.com>2007-04-20 08:55:52 +0200
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-04-20 22:56:29 -0700
commita993800655ee516b6f6a6fc4c2ee13fedfb0590b (patch)
tree023b362b4b30bddf2232ade83d162a84ac88f74b /block/cfq-iosched.c
parent46fcc86dd71d70211e965102fb69414c90381880 (diff)
downloadlinux-2.6.34-ux500-a993800655ee516b6f6a6fc4c2ee13fedfb0590b.tar.gz
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>
Diffstat (limited to 'block/cfq-iosched.c')
-rw-r--r--block/cfq-iosched.c34
1 files changed, 19 insertions, 15 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index b6491c020f2..9e3797167c8 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);