Subject: Re: Network performance with small packets

From: Shirley Ma <[email-masked]>
Date: Thu, 03 Feb 2011 07:58:00 -0800

On Thu, 2011-02-03 at 08:13 +0200, Michael S. Tsirkin wrote:
> > Initial TCP_STREAM performance results I got for guest to local
> host 
> > 4.2Gb/s for 1K message size, (vs. 2.5Gb/s)
> > 6.2Gb/s for 2K message size, and (vs. 3.8Gb/s)
> > 9.8Gb/s for 4K message size. (vs.5.xGb/s)
> 
> What is the average packet size, # bytes per ack, and the # of
> interrupts
> per packet? It could be that just slowing down trahsmission
> makes GSO work better. 

There is no TX interrupts with dropping packet.

GSO/TSO is the key for small message performance, w/o GSO/TSO, the
performance is limited to about 2Gb/s no matter how big the message size
it is. I think any work we try here will increase large packet size
rate. BTW for dropping packet, TCP increased fast retrans, not slow
start. 

I will collect tcpdump, netstart before and after data to compare packet
size/rate w/o w/i the patch.

Thanks
Shirley