From 4ae11ae8f482ce2676281696769d3c496a6e5190 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 12 Jan 2016 16:24:16 +0100 Subject: [PATCH] cfq-iosched: Reorder checks in cfq_should_preempt() Move check for preemption by rt class up. There is no functional change but it makes arguing about conditions simpler since we can be sure both cfq queues are from the same ioprio class. Acked-by: Tejun Heo Signed-off-by: Jan Kara Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 0a6a70a9bca85..2544c219c00c0 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -3959,6 +3959,13 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, if (cfq_slice_used(cfqq)) return true; + /* + * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. + */ + if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq)) + return true; + + WARN_ON_ONCE(cfqq->ioprio_class != new_cfqq->ioprio_class); /* Allow preemption only if we are idling on sync-noidle tree */ if (cfqd->serving_wl_type == SYNC_NOIDLE_WORKLOAD && cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD && @@ -3973,12 +3980,6 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, if ((rq->cmd_flags & REQ_PRIO) && !cfqq->prio_pending) return true; - /* - * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. - */ - 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; -- 2.39.5