cfq-iosched: tweak kick logic a bit more
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>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index e59f210..579f318 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1905,10 +1905,13 @@
* 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);
}