From 355b659c87432a4e76160640625c47fcf9174e8d Mon Sep 17 00:00:00 2001 From: Corrado Zoccolo Date: Thu, 8 Oct 2009 08:43:32 +0200 Subject: cfq-iosched: avoid probable slice overrun when idling If the average think time is larger than the remaining time slice for any given queue, don't allow it to idle. A succesful idle also means that we need to dispatch and complete a request, so if we don't even have time left for the idle process, we would overrun the slice in any case. Signed-off-by: Corrado Zoccolo Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'block') diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index a592afcf1e6..069a61017c0 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1093,6 +1093,15 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd) if (!cic || !atomic_read(&cic->ioc->nr_tasks)) return; + /* + * If our average think time is larger than the remaining time + * slice, then don't idle. This avoids overrunning the allotted + * time slice. + */ + if (sample_valid(cic->ttime_samples) && + (cfqq->slice_end - jiffies < cic->ttime_mean)) + return; + cfq_mark_cfqq_wait_request(cfqq); /* -- cgit v1.2.3