WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] Writing to a ramdisk in a PV domain is SLLLOOOWWW?!?

To: "Santos, Jose Renato G" <joserenato.santos@xxxxxx>
Subject: Re: [Xen-devel] Writing to a ramdisk in a PV domain is SLLLOOOWWW?!?
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Thu, 06 May 2010 15:26:10 -0700
Cc: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "Xen-Devel \(xen-devel@xxxxxxxxxxxxxxxxxxx\)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Thu, 06 May 2010 15:27:08 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <EF547E542C520A4D858CFEF5B404D053676ADD1C60@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <89f1cead-b77d-4294-ab12-5e05344ed346@default 4BE2FF9D.9010500@xxxxxxxx> <0e439ebe-9e32-41b9-b409-9d445debee47@default> <EF547E542C520A4D858CFEF5B404D053676ADD1C60@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100430 Fedora/3.0.4-2.fc12 Lightning/1.0b2pre Thunderbird/3.0.4
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

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel