From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH RFC] blkcg: prepare blkcg knobs for default hierarchy
Date: Fri, 23 May 2014 13:39:57 -0400
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To: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, linux-kernel@vger.kernel.org, Li Zefan <lizefan@huawei.com>, cgroups@vger.kernel.org

Hello, Vivek.

On Wed, Apr 23, 2014 at 03:21:09PM -0400, Vivek Goyal wrote:
> What about sync/async differentiation? Throttling layer seems to flag a request sync
> only if bio->bi_rw flag has REQ_SYNC set. While CFQ seems to consider
> request sync if bio is either read or bio->bi_rw has REQ_SYNC flag set.

Working on this again, AFAICS, both treat REQ_SYNC the same way as far
as stats are concerned.  If SYNC is set, it's sync; otherwise, it's
accounted as async whether read or write.

Thanks.

-- 
tejun