Message-ID: <40670A36.3000005@pobox.com>
Date: Sun, 28 Mar 2004 12:24:06 -0500
From: Jeff Garzik <jgarzik@pobox.com>
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To: Jamie Lokier <jamie@shareable.org>
CC: Nick Piggin <nickpiggin@yahoo.com.au>, linux-ide@vger.kernel.org,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH] speed up SATA
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Jamie Lokier wrote:
> Jeff Garzik 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.
> 
> 
> Does TCQ-on-write allow you to do ordered write commits, as with barriers,
> but without needing full cache flushes, and still get good performance?

Nope, TCQ is just a bunch of commands rather than one.  There are no 
special barrier indicators you can pass down with a command.

	Jeff


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