Date: Sat, 27 Mar 2004 17:02:57 -0800
From: Andrew Morton <akpm@osdl.org>
To: Jeff Garzik <jgarzik@pobox.com>
Cc: nickpiggin@yahoo.com.au, linux-ide@vger.kernel.org,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] speed up SATA
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Jeff Garzik <jgarzik@pobox.com> wrote:
>
>  TCQ-on-write for ATA disks is yummy because you don't really know what 
>  the heck the ATA disk is writing at the present time.  By the time the 
>  Linux disk scheduler gets around to deciding it has a nicely merged and 
>  scheduled set of requests, it may be totally wrong for the disk's IO 
>  scheduler.  TCQ gives the disk a lot more power when the disk integrates 
>  writes into its internal IO scheduling.

Slightly beneficial for throughput, disastrous for latency.

It appears the only way we'll ever get this gross misdesign fixed is to add
a latency test to winbench.

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