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-users

Re: [Xen-users] Xen 3.1 64bit / 32bit domU performance

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Xen 3.1 64bit / 32bit domU performance
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Wed, 22 Aug 2007 18:20:40 +0100
Cc: Stephan Seitz <s.seitz@xxxxxxxxxxxx>
Delivery-date: Wed, 22 Aug 2007 10:21:19 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <46CAD058.4010308@xxxxxxxxxxxx>
List-help: <mailto:xen-users-request@lists.xensource.com?subject=help>
List-id: Xen user discussion <xen-users.lists.xensource.com>
List-post: <mailto:xen-users@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
References: <46CAD058.4010308@xxxxxxxxxxxx>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: KMail/1.9.6
> I'm going to install Xen on a new 64bit capable machine with 16GB RAM and
> two quad-core Xeon. The domU's are (for migration issues) all 32bit PAE PV.
> My question is, should I install a 32bit PAE (which i prefer) or a 64bit
> Xen? Are there any known performance issues running 32bit PAE PV's on a
> 64bit Xen? It's really unlikely that the machine will be upgraded to more
> than 16GB.

AFAIK, 32-bit PAE PV guests should perform well on 64-bit Xen - if anything, 
they might well be better performing than 64-bit guests.  This is because 
protecting Xen from 64-bit guests incurs a higher performance penalty than 
for protecting it from 32-bit guests.

By the way, I don't think it's possible to suspend / resume or live migrate 
32-bit PV guests on a 64-bit Xen yet.  I guess that'll be in a future 
release.  Also, I understand that pre-3.1 32-bit kernels won't run on vanilla 
3.1, but subsequent patches that are in the -unstable tree provide 
compatibility for these older kernel builds too.

HVM guests are a separate issue, by the way, as their memory etc is handled 
differently.

> And btw. does someone know if the 32bit PAE PV domU's memory limit is also
> at 16GB or smaller (well, assuming more physical RAM)?

I'm not sure on this.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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

<Prev in Thread] Current Thread [Next in Thread>