Re: TCP_STREAM performance regression on commit b3613118

Eric Dumazet
2012-03-06T12:01:28Z

Le mardi 06 mars 2012 à 16:26 +0800, Jason Wang a écrit :
> On 03/06/2012 04:11 PM, Feng Tang wrote:
> > On Thu, Mar 01, 2012 at 10:07:43PM -0500, David Miller wrote:
> >> > From: Alex Shi<alex.shi@intel.com>
> >> > Date: Fri, 02 Mar 2012 10:45:17 +0800
> >> >
> >>> > > Add CC to tang feng, He is working on this issue.
> >> >
> >> > Is he? I'm pretty sure this is due to the TCP receive window growing
> >> > issue Eric Dumazet, Neal Cardwell and I are discussing in the thread
> >> > starting at:
> >> >
> >> > http://marc.info/?l=linux-netdev&m=132916352815286&w=2
> > Yes, probably, as we did find some clue related with the tcp_r/wmem.
> >
> > Here is the regression we found:
> > On some machines, we found there is about 10% resgression of netperf
> > TCP-64K loopback test between 3.2 and 3.3-rc1. The exact test is:
> > ./netperf -t TCP_STREAM -l 60 -H 127.0.0.1 -i 50,3 -I 99,5 -- -s 32768 -S 32768 -m 4096
> >
> >
> > The test machine is a 2 socket Quad Core Core 2 Duo server(2.66GHz) with
> > 8 GB RAM. Following are the debug info (ifconfig/netstat -s/tcp_rwmem)
> > before and after the test:
> >
> > The most obvious differences I can see are:
> > 1) 311 GB vs 241 GB from ifconfig
> > 2) the difference of the tcp_r/wmem
>
> Hi:
>
> Could you try the newest kernel? Looks like the difference has been
> already fixed by commit c43b874d5d714f271b80d4c3f49e05d0cbf51ed2.
>

Most likely yes.

tcp_rmem
4096 87380 87380
tcp_wmem
4096 16384 65536

Is way pessimistic :(