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Re: [Xen-devel] dom0 kernel v2.6.32.41 network problem

To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Subject: Re: [Xen-devel] dom0 kernel v2.6.32.41 network problem
From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Date: Fri, 15 Jul 2011 19:36:41 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Hui Kang <hkang@xxxxxxxxxxxxxxxxx>
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On Fri, 2011-07-15 at 19:19 +0100, Konrad Rzeszutek Wilk wrote:
> On Fri, Jul 15, 2011 at 05:54:11PM +0000, Hui Kang wrote:
> > Hi,
> > I am running two hosts with xen-4.0.1 and dom0 kernel The two 
> > hosts are connected to a Gigbit switch. Then I use iperf to measure the 
> > bandwidth and got the results of 200Mbit/second, which is only 1/5 of the 
> > available bandwidth.
> > Then I boot these two hosts using a vanilla kernel of The iperf 
> > reports 937Mbis/s, which is very close to the available link bandwidth.
> > So why the pvops dom0 kernel performs so bad? Does anyone observe similar 
> > problem? Thanks.

It is definitely worth checking that you don't have any debug options
enabled in your kernel .config. Some of those options are far more
expensive under Xen than native. (unfortunately I'm drawing a blank on
precisely which options we've seen this with right now, anything to do
with debugging page allocations etc would be a good bet).


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