Re: [Re: [Xen-users] Slow domU network

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Fri, Mar 10, 2006 at 10:43:17AM +0100, Artur Schiefer wrote:
> hello,
> 
> somehow the linux network core tries to adjust itself to its
> environment. as i recently learned theese parameters are optimized for
> 100 mbit networking. from another poster i got the info that you have to
> set the following parameters in your "/etc/sysctl.conf" to achieve gbit
> speed:
> # increase TCP maximum buffer size
> net.core.rmem_max=16777216
> net.core.wmem_max=16777216
> 
> # increase Linux autotuning TCP buffer limits
> # min, default, and maximum number of bytes to use
> net.ipv4.tcp_rmem=4096 87380 16777216
> net.ipv4.tcp_wmem=4096 65536 16777216
> 
> BUT THIS ONLY SOLVES THE PROBLEM FOR WITHIN DOMU COMMUNCATION (i.e.
> sender and receiver are the SAME virtual maschine, which should be a
> theoretical problem in most cases). I tuned domU and dom0 this way
> problem between dom0 and domU still exists. i also played with tcp
> window sizes (-w option in iperf) from 64kb to 2MB but the performance
> differences are negligable.
>

OK. Thanks.

Did you try iperf in UDP mode between dom0 and domU?  

server: iperf -s -u -i 1
client: iperf -c server_ip -u -b 90M -t 20

to check for packet loss @ 90 Mbit/sec for 20 seconds.

- Pasi
 
> 
> Am Donnerstag, den 09.03.2006, 20:38 +0200 schrieb Pasi Kärkkäinen:
> > On Thu, Mar 09, 2006 at 05:26:03PM +0100, Artur Schiefer wrote:
> > > ok, solved the problem for within domu communcation, was an autotuning
> > > effect.
> > > 
> > 
> > Autotuning effect? Please be more specific because many of the xen users
> > seem to have problems with network performance..
> > 
> > -- Pasi
> >        
> >                                    ^
> >                                 .     .
> >                                  Linux
> >                               /    -    \
> >                              Choice.of.the
> >                            .Next.Generation.
> > 
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-users
> 


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