linux-kernel - Re: performance drop after using blkcg

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Message-ID: <20121211142742.GE7084@htj.dyndns.org>
Date:	Tue, 11 Dec 2012 06:27:42 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	Zhao Shuai <zhaoshuai@...ebsd.org>, axboe@...nel.dk,
	ctalbott@...gle.com, rni@...gle.com, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org, containers@...ts.linux-foundation.org
Subject: Re: performance drop after using blkcg

On Tue, Dec 11, 2012 at 09:25:18AM -0500, Vivek Goyal wrote:
> In general, do not use blkcg on faster storage. In current form it
> is at best suitable for single rotational SATA/SAS disk. I have not
> been able to figure out how to provide fairness without group idling.

I think cfq is just the wrong approach for faster non-rotational
devices.  We should be allocating iops instead of time slices.

Thanks.

-- 
tejun
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