Re: [Xen-devel] Network performance - sending from VM to VM using TCP

[Kip Macy <kmacy@xxxxxxxxxx>]

Are you using FreeBSD or Linux?

On Thu, 26 May 2005, Cherie Cheung wrote:

> Hi,
> 
> I have been simulating a network using dummynet and evaluating it
> using netperf. Xen3.0-unstable is used and the VMs are
> vmlinuz-2.6.11-xenU. The simulated link is 300Mbps with 80ms RTT.
> Using netperf, I sent data using TCP from domain-0 of machine 1 to
> domain-0 of machine 2. Then I repeat the experiment, but this time
> from VM-1 of machine 1 to VM-1 of machine 2.
> 
> However, the performance across the two VMs is substantially worse
> than that across domain-0. Here's the result:
> 
> FROM VM to VM:
> TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to dw10.ucsd.edu
> (172.19.222.210) port 0 AF_INET
> Recv   Send    Send                          
> Socket Socket  Message  Elapsed              
> Size   Size    Size     Time     Throughput  
> bytes  bytes   bytes    secs.    10^6bits/sec  
> 
>  87380  65536  65536    80.28      24.83 
> 
> 
> FROM domain-0 to domain-0:
> TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to damp.ucsd.edu
> (137.110.222.236) port 0 AF_INET
> Recv   Send    Send                          
> Socket Socket  Message  Elapsed              
> Size   Size    Size     Time     Throughput  
> bytes  bytes   bytes    secs.    10^6bits/sec  
> 
>  87380  65536  65536    80.11     280.62 
> 
> Here's the setting of the network buffer:
> 
> net.core.wmem_max = 8388608
> net.core.rmem_max = 8388608
> net.ipv4.tcp_bic = 1
> net.ipv4.tcp_rmem = 4096        87380   8388608
> net.ipv4.tcp_wmem = 4096        65536   8388608
> 
> Does anyone know why the performance across two VMs is so bad? Any fix
> to it? Thank you.
> 
> Cherie
> 
> _______________________________________________
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> http://lists.xensource.com/xen-devel
> 

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