From: Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>
To: Jeff Garzik <jgarzik@pobox.com>
Subject: Re: [PATCH] speed up SATA
Date: Sun, 28 Mar 2004 01:13:58 +0100
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Cc: Stefan Smietanowski <stesmi@stesmi.com>, linux-ide@vger.kernel.org,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>
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On Sunday 28 of March 2004 00:40, Jeff Garzik wrote:
> Jeff Garzik wrote:
> > That's the main limitation on request size right now...  libata limits
> > S/G table entries to 128[1], so a perfectly aligned, fully merged
>
>     ...
>
> [1] because even though the block layer properly splits on segment
> boundaries, pci_map_sg() may violate those boundaries (James B and
> others are working on fixing this).  So...  for right now the driver
> must check the s/g entry boundaries after DMA mapping, and split them
> (again) if necessary.  IDE does this in ide_build_dmatable().

You are right but small clarification is needed: code in ide_build_dmatable()
predates segment boundary support in block layer (IDE never relied on it).

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