linux-kernel - Re: TCP_STREAM performance regression on commit b3613118

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Date:	Tue, 06 Mar 2012 04:01:28 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	Feng Tang <feng.tang@...el.com>,
	David Miller <davem@...emloft.net>, alex.shi@...el.com,
	linux-kernel@...r.kernel.org, tim.c.chen@...el.com,
	ying.huang@...el.com, netdev@...r.kernel.org
Subject: Re: TCP_STREAM performance regression on commit b3613118

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@...el.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 :(




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