Subject: Re: [RFC PATCH v9 00/16] Provide a zero-copy method on KVM
 virtio-net.
From: Shirley Ma <mashirle@us.ibm.com>
To: xiaohui.xin@intel.com
Cc: netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        mst@redhat.com, mingo@elte.hu, davem@davemloft.net,
        herbert@gondor.hengli.com.au, jdike@linux.intel.com
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Date: Tue, 10 Aug 2010 23:01:00 -0700
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On Tue, 2010-08-10 at 18:43 -0700, Shirley Ma wrote:
> > Also I found some vhost performance regression on the new
> > kernel with tuning. I used to get 9.4Gb/s, now I couldn't get it. 
> 
> I forgot to mention the kernel I used 2.6.36 one. And I found the
> native
> host BW is limited to 8.0Gb/s, so the regression might come from the
> device driver not vhost.

Something is very interesting, when binding ixgbe interrupts to cpu1,
and running netperf/netserver on cpu0, the native host to host
performance is still around 8.0Gb/s, however, the macvtap zero copy
result is 9.0Gb/s.

root@localhost ~]# netperf -H 192.168.10.74 -c -C -l60 -T0,0 -- -m 64K
TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.10.74 (192.168..
10.74) port 0 AF_INET : cpu bind
Recv   Send    Send                          Utilization       Service Demand
Socket Socket  Message  Elapsed              Send     Recv     Send    Recv
Size   Size    Size     Time     Throughput  local    remote   local   remote
bytes  bytes   bytes    secs.    10^6bits/s  % S      % S      us/KB   us/KB

 87380  16384  65536    60.00      9013.59   53.01    8.21     0.963   0.597

Below is perf top output:

              578.00  6.5% copy_user_generic_string   
              381.00  4.3% vmx_vcpu_run                
              250.00  2.8% schedule                    
              207.00  2.3% vhost_get_vq_desc           
              204.00  2.3% _raw_spin_lock_irqsave      
              197.00  2.2% translate_desc              
              193.00  2.2% memcpy_fromiovec            
              162.00  1.8% gup_pte_range   

We can compare your results with mine to see any difference.

Thanks
Shirley

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