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cfq-iosched: tweak kick logic a bit more

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We only kick the dispatch for an idling queue, if we think it's a
(somewhat) fully merged request. Also allow a kick if we have other
busy queues in the system, since we don't want to risk waiting for
a potential merge in that case. It's better to get some work done and
proceed.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe 2009-04-15 12:12:46 +02:00
parent 40bb54d197
commit 2d87072296
1 changed files with 5 additions and 2 deletions
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7
block/cfq-iosched.c
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@ -1905,10 +1905,13 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
* of tiny requests, because we disrupt the normal plugging
* and merging. If the request is already larger than a single
* page, let it rip immediately. For that case we assume that
* merging is already done.
* merging is already done. Ditto for a busy system that
* has other work pending, don't risk delaying until the
* idle timer unplug to continue working.
*/
if (cfq_cfqq_wait_request(cfqq)) {
if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE) {
if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
cfqd->busy_queues > 1) {
del_timer(&cfqd->idle_slice_timer);
blk_start_queueing(cfqd->queue);
}