From: Jeremy Fitzhardinge <jeremy@goop.org>
To: "Santos, Jose Renato G" <joserenato.santos@hp.com>
Cc: Dan Magenheimer <dan.magenheimer@oracle.com>,
"Xen-Devel (xen-devel@lists.xensource.com)"
<xen-devel@lists.xensource.com>
Subject: Re: Writing to a ramdisk in a PV domain is SLLLOOOWWW?!?
Date: Thu, 06 May 2010 15:26:10 -0700 [thread overview]
Message-ID: <4BE34202.9030406@goop.org> (raw)
In-Reply-To: <EF547E542C520A4D858CFEF5B404D053676ADD1C60@GVW0673EXC.americas.hpqcorp.net>
On 05/06/2010 03:04 PM, Santos, Jose Renato G wrote:
> This is complete wild guess, but could it be that you are doing multi-page I/O with non contiguous machine pages?
> I believe the DMA API for pv guests uses swioltlb which does extra copies to a bounce buffer if you request a dma address to a multi-page region (as the pages may be non contiguous).
>
Ramdisk access shouldn't be going anywhere near DMA API or swiotlb.
J
prev parent reply other threads:[~2010-05-06 22:26 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-05 18:14 Writing to a ramdisk in a PV domain is SLLLOOOWWW?!? Dan Magenheimer
2010-05-05 20:16 ` Dan Magenheimer
2010-05-06 17:42 ` Jeremy Fitzhardinge
2010-05-06 21:02 ` Dan Magenheimer
2010-05-06 22:04 ` Santos, Jose Renato G
2010-05-06 22:26 ` Jeremy Fitzhardinge [this message]
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