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/
Home Products Support Community News


Re: [Xen-users] Re: Performance Issues: I/O Wait

To: <s.seitz@xxxxxxxxxxxx>
Subject: Re: [Xen-users] Re: Performance Issues: I/O Wait
From: "Nick Couchman" <Nick.Couchman@xxxxxxxxx>
Date: Tue, 23 Oct 2007 20:55:18 -0600
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Delivery-date: Tue, 23 Oct 2007 19:56:13 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
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>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
Thanks for the tips - I'll give them a try.  One clarification - for
disabling transmission checksums, is that inside the domU or inside

Some of the tests was using NFS, but lately I've been testing with iSCSI
and even local block devices and it seems to happen on those, too,
though not to the same degree.


Nick Couchman
SEAKR Engineering, Inc.
6221 South Racine Circle
Centennial, CO 80111
Main: (303) 790-8499
Fax: (303) 790-8720
Web: http://www.seakr.com
>>> Stephan Seitz <s.seitz@xxxxxxxxxxxx> 10/23/07 8:03 PM >>>
Nick Couchman schrieb:
> Hi, again...haven't had any responses to this, yet.
> Thanks,
> Nick


have you tried to pin your vCPU's to dedicated Cores?
It might be suboptimal if a domU uses.. say core 0 of
cpu 0 and core 0 of cpu 1 ... or anything not on the
same cpu.
e.g. use the second cpu on a 2x dualcore system
count starts at 0.
cpus = [ 2,3 ]

If your domU is bridged, you might try to disable
transmission checksums on the NIC's.
ethtool -K [nicname] tx off

Anyway, you mentioned high I/O latency due to network
issues. Is your domU using some kind of NFS or something?
Btw. I might missed this part, but are you using PV or
HVM guests?


Stephan Seitz
Senior System Administrator

*netz-haut* e.K.
multimediale kommunikation

zweierweg 22
97074 würzburg

fon: +49 931 2876247
fax: +49 931 2876248

web: www.netz-haut.de <http://www.netz-haut.de/>

registriergericht: amtsgericht würzburg, hra 5054

Xen-users mailing list