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

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Message-ID: <20091002182608.GO31616@kernel.dk>
Date:	Fri, 2 Oct 2009 20:26:08 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Mike Galbraith <efault@....de>
Cc:	Ingo Molnar <mingo@...e.hu>,
	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

On Fri, Oct 02 2009, Mike Galbraith wrote:
> On Fri, 2009-10-02 at 20:04 +0200, Jens Axboe wrote:
> 
> > I'm not too crazy about it either. How about just using 'desktop' since
> > this is obviously what we are really targetting? 'latency' isn't fully
> > descriptive either, since it may not necessarily provide the best single
> > IO latency (noop would).
> 
> Grin. "Perfect is the enemy of good" :)
>                                                   Avg
>      16.24   175.82   154.38   228.97   147.16  144.5     noop
>      43.23    57.39    96.13   148.25   180.09  105.0     deadline

Yep, that's where it falls down. Noop basically fails here because it
treats all IO as equal, which obviously isn't true for most people. But
even for pure read workloads (is the above the mixed read/write, or just
read?), latency would be excellent with noop but the desktop experience
would not.

-- 
Jens Axboe

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