linux-kernel - Re: IO scheduler based IO controller V10

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Date:	Sat, 3 Oct 2009 11:01:35 +0200
From:	Corrado Zoccolo <czoccolo@...il.com>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Mike Galbraith <efault@....de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Vivek Goyal <vgoyal@...hat.com>,
	Ulrich Lukas <stellplatz-nr.13a@...enparkplatz.de>,
	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, dm-devel@...hat.com,
	nauman@...gle.com, dpshah@...gle.com, lizf@...fujitsu.com,
	mikew@...gle.com, fchecconi@...il.com, paolo.valente@...more.it,
	ryov@...inux.co.jp, fernando@....ntt.co.jp, jmoyer@...hat.com,
	dhaval@...ux.vnet.ibm.com, balbir@...ux.vnet.ibm.com,
	righi.andrea@...il.com, m-ikeda@...jp.nec.com, agk@...hat.com,
	akpm@...ux-foundation.org, peterz@...radead.org,
	jmarchan@...hat.com, riel@...hat.com
Subject: Re: IO scheduler based IO controller V10

Hi Jens,
On Sat, Oct 3, 2009 at 9:25 AM, Jens Axboe <jens.axboe@...cle.com> wrote:
> On Sat, Oct 03 2009, Ingo Molnar wrote:
>>
>> * Mike Galbraith <efault@....de> wrote:
>>
>> >     unsigned int cfq_desktop;
>> > +   unsigned int cfq_desktop_dispatch;
>>
>> > -   if (cfq_cfqq_idle_window(cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
>> > +   if (cfq_cfqq_idle_window(cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC]) {
>> > +           cfqd->desktop_dispatch_ts = jiffies;
>> >             return 0;
>> > +   }
>>
>> btw., i hope all those desktop_ things will be named latency_ pretty
>> soon as the consensus seems to be - the word 'desktop' feels so wrong in
>> this context.
>>
>> 'desktop' is a form of use of computers and the implication of good
>> latencies goes far beyond that category of systems.
>
> I will rename it, for now it doesn't matter (lets not get bogged down in
> bike shed colors, please).
>
> Oh and Mike, I forgot to mention this in the previous email - no more
> tunables, please. We'll keep this under a single knob.

Did you have a look at my http://patchwork.kernel.org/patch/47750/ ?
It already introduces a 'target_latency' tunable, expressed in ms.

If we can quantify the benefits of each technique, we could enable
them based on the target latency requested by that single tunable.

Corrado

>
> --
> Jens Axboe
>
> --
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-- 
__________________________________________________________________________

dott. Corrado Zoccolo                          mailto:czoccolo@...il.com
PhD - Department of Computer Science - University of Pisa, Italy
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