Date: Wed, 30 Dec 2009 19:45:35 +0100
From: Jens Axboe <jens.axboe@oracle.com>
To: Corrado Zoccolo <czoccolo@gmail.com>
Cc: Linux-Kernel <linux-kernel@vger.kernel.org>,
       Jeff Moyer <jmoyer@redhat.com>, Vivek Goyal <vgoyal@redhat.com>,
       Shaohua Li <shaohua.li@intel.com>,
       Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Subject: Re: [PATCH] cfq-iosched: non-rot devices do not need queue merging
Message-ID: <20091230184535.GE4489@kernel.dk>
References: <1262175004-2132-1-git-send-email-czoccolo@gmail.com>
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On Wed, Dec 30 2009, Corrado Zoccolo wrote:
> Non rotational devices' performances are not affected by
> distance of requests, so there is no point in having overhead
> to merge queues of nearby requests.

If the distance is zero, it may still make a big difference (at least
for writes). This check would be better as "ncq and doesn't suck", ala

        blk_queue_nonrot(q) && tagged

like we do elsewhere.

-- 
Jens Axboe

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