cfq-iosched: avoid probable slice overrun when idling (355b659c) · Commits · 戴 / test

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 <czoccolo@gmail.com> Signed-off-by:

Jens Axboe <jens.axboe@oracle.com>

block/cfq-iosched.c

+9 −0

Original line number	Original line	Diff line number	Diff line
	@@ -1093,6 +1093,15 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
	if (!cic \|\| !atomic_read(&cic->ioc->nr_tasks))		if (!cic \|\| !atomic_read(&cic->ioc->nr_tasks))
	return;		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);		cfq_mark_cfqq_wait_request(cfqq);

	/*		/*

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