lkml.org 
[lkml]   [2010]   [Jul]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 2/3] cfq-iosched: Implement a tunable group_idle
Date
Vivek Goyal <vgoyal@redhat.com> writes:

> o Implement a new tunable group_idle, which allows idling on the group
> instead of a cfq queue. Hence one can set slice_idle = 0 and not idle
> on the individual queues but idle on the group. This way on fast storage
> we can get fairness between groups at the same time overall throughput
> improves.
>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> ---
[snip]
> @@ -1929,13 +1941,21 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
> return;
> }
>
> + /* There are other queues in the group, don't do group idle */
> + if (group_idle && cfqq->cfqg->nr_cfqq > 1)
> + return;
> +
> cfq_mark_cfqq_wait_request(cfqq);
>
> - sl = cfqd->cfq_slice_idle;
> + if (group_idle)
> + sl = cfqd->cfq_group_idle;
> + else
> + sl = cfqd->cfq_slice_idle;

What happens when both group_idle and slice_idle are set? Is that a
sane thing to do from a user's perspective? If not, please protect
against it in the configuration code. If so, then explain why we prefer
group_idle here, but slice_idle in completed request for the extend_sl:

> @@ -3425,7 +3458,10 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
> * the queue.
> */
> if (cfq_should_wait_busy(cfqd, cfqq)) {
> - cfqq->slice_end = jiffies + cfqd->cfq_slice_idle;
> + unsigned long extend_sl = cfqd->cfq_slice_idle;
> + if (!cfqd->cfq_slice_idle)
> + extend_sl = cfqd->cfq_group_idle;
> + cfqq->slice_end = jiffies + extend_sl;

Also, you'll need to add documentation for this new tunable.

Cheers,
Jeff


\
 
 \ /
  Last update: 2010-07-21 21:43    [from the cache]
©2003-2011 Jasper Spaans