From: Christoph Hellwig <hch@infradead.org>
To: James Bottomley <James.Bottomley@SteelEye.com>
Cc: Mark Haverkamp <markh@osdl.org>,
linux-scsi <linux-scsi@vger.kernel.org>,
Mark Salyzyn <mark_salyzyn@adaptec.com>
Subject: Re: [PATCH 3/5] aacraid: update dma mapping
Date: Wed, 30 Nov 2005 18:49:51 +0000 [thread overview]
Message-ID: <20051130184951.GA18583@infradead.org> (raw)
In-Reply-To: <1133376327.3312.43.camel@mulgrave>
On Wed, Nov 30, 2005 at 12:45:27PM -0600, James Bottomley wrote:
> On Wed, 2005-11-30 at 10:36 -0800, Mark Haverkamp wrote:
> > This patch changes map_single to map_page in compliance with
> > recommendations made in the IO-Perf howto document to prevent bounce
> > buffering of DMA requests.
>
> Erm, there's a misunderstanding somewhere. You're replacing correct
> pci_map_single calls with its more difficult to use pci_map_page. This
> has absolutely zero performance impact and adds the risk that because
> pci_map_page is more complex to use, someone gets it wrong somewhere.
> Really, for block devices pci_map_single is the absolutely correct
> interface. pci_map_page should really only be used by the net stack for
> packet fragment mapping.
And the really nice thing is that this whole non-S/G I/O path will go away
completely for 2.6.16 :)
next prev parent reply other threads:[~2005-11-30 18:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-11-30 18:36 [PATCH 3/5] aacraid: update dma mapping Mark Haverkamp
2005-11-30 18:45 ` James Bottomley
2005-11-30 18:49 ` Christoph Hellwig [this message]
2005-11-30 18:55 ` Mark Haverkamp
-- strict thread matches above, loose matches on Subject: below --
2005-11-30 19:23 Salyzyn, Mark
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