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] databases and xen?

To: Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] databases and xen?
From: Matt Ayres <matta@xxxxxxxxxxxx>
Date: Tue, 18 Jan 2005 17:21:35 -0500
Cc: Rik van Riel <riel@xxxxxxxxxx>, Wim Coekaerts <wim.coekaerts@xxxxxxxxxx>, Nicholas Lee <nj.lee@xxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxxx
Delivery-date: Wed, 19 Jan 2005 01:34:07 +0000
Envelope-to: xen+James.Bulpin@xxxxxxxxxxxx
In-reply-to: <E1Cr0EE-00025M-00@xxxxxxxxxxxxxxxxx>
List-archive: <http://sourceforge.net/mailarchive/forum.php?forum=xen-devel>
List-help: <mailto:xen-devel-request@lists.sourceforge.net?subject=help>
List-id: List for Xen developers <xen-devel.lists.sourceforge.net>
List-post: <mailto:xen-devel@lists.sourceforge.net>
List-subscribe: <https://lists.sourceforge.net/lists/listinfo/xen-devel>, <mailto:xen-devel-request@lists.sourceforge.net?subject=subscribe>
List-unsubscribe: <https://lists.sourceforge.net/lists/listinfo/xen-devel>, <mailto:xen-devel-request@lists.sourceforge.net?subject=unsubscribe>
Organization: TekTonic
References: <E1Cr0EE-00025M-00@xxxxxxxxxxxxxxxxx>
Sender: xen-devel-admin@xxxxxxxxxxxxxxxxxxxxx
On Tue, 2005-01-18 at 20:45 +0000, Ian Pratt wrote:
> > On Mon, 17 Jan 2005, Wim Coekaerts wrote:
> > 
> > > testign it has already been fine. I ran 4 databases each in one domain
> > > (oracle10g) and it s been amazingly stable. I have not however done
> > > performance testing. soon...
> > 
> > How does O_DIRECT IO to xen block devices work ?
> 
> I'm not entirely sure quite what O_DIRECT is defined to do. It
> probably bypasses the guest's buffer cache OK, and gets turned
> into IO's in domain 0 without passing through the buffer cache
> (unless you're using a loop file or suchlike).
> 
> I believe IOs wont be acknowledged to the guest until they've
> been completed in dom0. However, they can be reordered. We
> probably need to add in a re-order barrier operation on the VBD
> device channel protocol in order to guarantee ordering where it
> matters (this would be marginally more efficient than
> holding back following requests in the guest).
> 

To avoid the buffercache problems of loopback images in dom0 you can
have dom0 open the loop files with O_DIRECT.  This should help
performance when using loop files as it eliminates the double buffering.

> 
> Ian
> 
> 
> -------------------------------------------------------
> The SF.Net email is sponsored by: Beat the post-holiday blues
> Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek.
> It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxxxx
> https://lists.sourceforge.net/lists/listinfo/xen-devel
-- 



-------------------------------------------------------
The SF.Net email is sponsored by: Beat the post-holiday blues
Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek.
It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.sourceforge.net/lists/listinfo/xen-devel