Re: [Xen-users] Xen and networking.

[Riccardo Veraldi <Riccardo.Veraldi@xxxxxxxxxxxx>]

if you want to get Gigabit performance on your domU (using HVM 
virtualization)
you MUST compile the xen unmodified_drivers (in particular Netfront) and 
load
those drivers as kernel modules on your domU.
Then you must change the guest machine xen file using netfront insted of 
ioemu
for the network interface. I have written a page on how to do it but it 
is written in italian.
Anyway if you follow the instruction you should understand looking at 
the bare commands.
https://calcolo.infn.it/wiki/doku.php?id=network_overbust_compilare_e_installare_il_kernel_module_con_il_supporto_netfront

of couse the xen source coude depends on the xen version you are using 
on your dom0.
Actually I was not satisfied of Xen 3.0.2 used on RHEL5 so we build rpm 
for Xen 3.1.2
and actually we are using those.

Rick


tmac ha scritto:
> I have a beefy machine
> (Intel dual-quad core, 16GB memory 2 x GigE)
>
> I have loaded RHEL5.1-xen on the hardware and have created two logical systems:
> 4 cpus, 7.5 GB memory 1 x Gige
>
> Following RHEL guidelines, I have it set up so that eth0->xenbr0 and
> eth1->xenbr1
> Each of the two RHEL5.1 guests uses one of the interfaces and this is
> verified at the
> switch by seeing the unique MAC addresses.
>
> If I do a crude test from one guest over nfs,
> dd if=/dev/zero of=/nfs/test bs=32768 count=32768
>
> This yields almost always 95-100MB/sec
>
> When I run two simultaneously, I cannot seem to get above 25MB/sec from each.
> It starts off with a large burst like each can do 100MB/sec, but then
> in a couple
> of seconds, tapers off to the 15-40MB/sec until the dd finishes.
>
> Things I have tried (installed on the host and the guests)
>
>  net.core.rmem_max = 16777216
>  net.core.wmem_max = 16777216
>  net.ipv4.tcp_rmem = 4096 87380 16777216
>  net.ipv4.tcp_wmem = 4096 65536 16777216
>
>  net.ipv4.tcp_no_metrics_save = 1
>  net.ipv4.tcp_moderate_rcvbuf = 1
>  # recommended to increase this for 1000 BT or higher
>  net.core.netdev_max_backlog = 2500
>  sysctl -w net.ipv4.tcp_congestion_control=cubic
>
> Any ideas?
>
>
>   

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