From: Corrado Zoccolo Date: Thu, 8 Oct 2009 06:43:32 +0000 (+0200) Subject: cfq-iosched: avoid probable slice overrun when idling X-Git-Tag: v2.6.32-rc5~26^2~6 X-Git-Url: http://ftp.safe.ca/?p=safe%2Fjmp%2Flinux-2.6;a=commitdiff_plain;h=355b659c87432a4e76160640625c47fcf9174e8d 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 --- diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index a592afc..069a610 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); /*