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

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Date:	Wed, 30 Sep 2009 16:24:47 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Mike Galbraith <efault@....de>
Cc:	Jens Axboe <jens.axboe@...cle.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, torvalds@...ux-foundation.org, mingo@...e.hu,
	riel@...hat.com
Subject: Re: IO scheduler based IO controller V10

On Wed, Sep 30, 2009 at 10:05:39PM +0200, Mike Galbraith wrote:
> 
>  
> >  		/*
> > +		 * We may have seeky queues, don't throttle up just yet.
> > +		 */
> > +		if (time_before(jiffies, cfqd->last_seeker + CIC_SEEK_THR))
> > +			return 0;
> > +
> 
> bzzzt.  Window too large, but the though is to let them overload, but
> not instantly.
> 

CIC_SEEK_THR is 8K jiffies so that would be 8seconds on 1000HZ system. Try
using one "slice_idle" period of 8 ms. But it might turn out to be too
short depending on the disk speed.

Thanks
Vivek
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