Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores

[Dietmar Maurer]

> Is the network path you are downloading across reasonably idle so that you
> get reproducible results between runs?

Also tested with netperf (to local host) now.

Results in short (performance in Mbit/sec):

vhost=off,cores=1: 3982
vhost=off,cores=2: 3930
vhost=off,cores=4: 3912

vhost=on,cores=1: 22065
vhost=on,cores=2: 1392
vhost=on,cores=4: 532

As you can see, vhost performance drops from 22065 to 532 -  this is by factor 
40!

And ideas?


-- complete logs---

With vhost=off / cores=1

# netperf -H maui
TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to maui.maurer-it.com 
(192.168.2.2) port 0 AF_INET : demo
Recv   Send    Send                          
Socket Socket  Message  Elapsed              
Size   Size    Size     Time     Throughput  
bytes  bytes   bytes    secs.    10^6bits/sec  

 87380  16384  16384    10.00    3982.74  


With vhost=off / cores=2

# netperf -H maui
TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to maui.maurer-it.com 
(192.168.2.2) port 0 AF_INET : demo
Recv   Send    Send                          
Socket Socket  Message  Elapsed              
Size   Size    Size     Time     Throughput  
bytes  bytes   bytes    secs.    10^6bits/sec  

 87380  16384  16384    10.00    3930.62   

With vhost=off / cores=4

# netperf -H maui
TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to maui.maurer-it.com 
(192.168.2.2) port 0 AF_INET : demo
Recv   Send    Send                          
Socket Socket  Message  Elapsed              
Size   Size    Size     Time     Throughput  
bytes  bytes   bytes    secs.    10^6bits/sec  

 87380  16384  16384    10.00    3912.36  


With vhost=on /cores=1

# netperf -H maui
TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to maui.maurer-it.com 
(192.168.2.2) port 0 AF_INET : demo
Recv   Send    Send                          
Socket Socket  Message  Elapsed              
Size   Size    Size     Time     Throughput  
bytes  bytes   bytes    secs.    10^6bits/sec  

 87380  16384  16384    10.00    22065.48 

With vhost=on /cores=2

# netperf -H maui
TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to maui.maurer-it.com 
(192.168.2.2) port 0 AF_INET : demo
Recv   Send    Send                          
Socket Socket  Message  Elapsed              
Size   Size    Size     Time     Throughput  
bytes  bytes   bytes    secs.    10^6bits/sec  

 87380  16384  16384    10.01    1392.61

With vhost=on /cores=4

# netperf -H maui
TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to maui.maurer-it.com 
(192.168.2.2) port 0 AF_INET : demo
Recv   Send    Send                          
Socket Socket  Message  Elapsed              
Size   Size    Size     Time     Throughput  
bytes  bytes   bytes    secs.    10^6bits/sec  

 87380  16384  16384    10.05     532.31