Message-ID: <406625D4.7090605@pobox.com>
Date: Sat, 27 Mar 2004 20:09:40 -0500
From: Jeff Garzik <jgarzik@pobox.com>
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To: Andrew Morton <akpm@osdl.org>
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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Andrew Morton wrote:
> 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.

If the disk is smart there are surely opportunities for latency 
optimization as well...


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

rotfl ;-)  True that...

"IOPs" are what make a lot of storage peeps excited these days, so they 
are being pushed in a low-latency direction anyway.

	Jeff


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