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authorShaohua Li <shaohua.li@intel.com>2010-11-08 15:01:03 +0100
committerJens Axboe <jaxboe@fusionio.com>2010-11-08 15:01:03 +0100
commitd2d59e18a1ea8ecdd1c0a52af320e9a7f5391cc4 (patch)
treeb39812dc8fd9ae552c361a84a10dcd61d2caaab5 /block
parentc1e44756fdb7b363fd22cb5514dced40752e36c5 (diff)
downloadlinux-linaro-precise-d2d59e18a1ea8ecdd1c0a52af320e9a7f5391cc4.tar.gz
cfq-iosched: schedule dispatch for noidle queue
A queue is idle at cfq_dispatch_requests(), but it gets noidle later. Unless other task explictly does unplug or all requests are drained, we will not deliever requests to the disk even cfq_arm_slice_timer doesn't make the queue idle. For example, cfq_should_idle() returns true because of service_tree->count == 1, and then other queues are added. Note, I didn't see obvious performance impacts so far with the patch, but just thought this could be a problem. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'block')
-rw-r--r--block/cfq-iosched.c23
1 files changed, 22 insertions, 1 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index b8174bb4a6a..986865e3fbc 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3255,6 +3255,10 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
return true;
+ /* An idle queue should not be idle now for some reason */
+ if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))
+ return true;
+
if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
return false;
@@ -3508,8 +3512,25 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
}
}
- if (!cfqd->rq_in_driver)
+ if (!cfqd->rq_in_driver) {
+ cfq_schedule_dispatch(cfqd);
+ return;
+ }
+ /*
+ * A queue is idle at cfq_dispatch_requests(), but it gets noidle
+ * later. We schedule a dispatch if the queue has no requests,
+ * otherwise the disk is actually in idle till all requests
+ * are finished even cfq_arm_slice_timer doesn't make the queue idle
+ * */
+ cfqq = cfqd->active_queue;
+ if (!cfqq)
+ return;
+
+ if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq) &&
+ (!cfqd->cfq_group_idle || cfqq->cfqg->nr_cfqq > 1)) {
+ cfq_del_timer(cfqd, cfqq);
cfq_schedule_dispatch(cfqd);
+ }
}
/*