From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: performance drop after using blkcg
Date: Tue, 11 Dec 2012 06:27:42 -0800
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To: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, ctalbott-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, rni-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Zhao Shuai <zhaoshuai-h+KGxgPPiopAfugRpC6u6w@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org

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