cfq-iosched: cleanup unreachable code (c16632ba) · Commits · 戴 / test

cfq_should_idle returns false for no-idle queues that are not the last, so the control flow will never reach the removed code in a state that satisfies the if condition. The unreachable code was added to emulate previous cfq behaviour for non-NCQ rotational devices. My tests show that even without it, the performances and fairness are comparable with previous cfq, thanks to the fact that all seeky queues are grouped together, and that we idle at the end of the tree. Signed-off-by:

Corrado Zoccolo <czoccolo@gmail.com> Acked-by:

Vivek Goyal <vgoyal@redhat.com> Signed-off-by:

Jens Axboe <jens.axboe@oracle.com>

block/cfq-iosched.c

+0 −13

Original line number	Original line	Diff line number	Diff line
	@@ -1269,19 +1269,6 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
	cfq_mark_cfqq_wait_request(cfqq);		cfq_mark_cfqq_wait_request(cfqq);

	sl = cfqd->cfq_slice_idle;		sl = cfqd->cfq_slice_idle;
	/* are we servicing noidle tree, and there are more queues?
	* non-rotational or NCQ: no idle
	* non-NCQ rotational : very small idle, to allow
	* fair distribution of slice time for a process doing back-to-back
	* seeks.
	*/
	if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
	service_tree_for(cfqd->serving_prio, SYNC_NOIDLE_WORKLOAD, cfqd)
	->count > 0) {
	if (blk_queue_nonrot(cfqd->queue) \|\| cfqd->hw_tag)
	return;
	sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
	}

	mod_timer(&cfqd->idle_slice_timer, jiffies + sl);		mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
	cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);		cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);

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