linux-kernel - Re: UDP-U stream performance regression on 32-rc1 kernel

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Date:	Thu, 05 Nov 2009 09:10:57 +0100
From:	Mike Galbraith <efault@....de>
To:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...e.hu>, alex.shi@...el.com,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: UDP-U stream performance regression on 32-rc1 kernel

On Thu, 2009-11-05 at 15:44 +0800, Zhang, Yanmin wrote:
> On Thu, 2009-11-05 at 06:20 +0100, Mike Galbraith wrote:
> > On Thu, 2009-11-05 at 10:20 +0800, Zhang, Yanmin wrote:
> > > On Wed, 2009-11-04 at 13:07 +0100, Mike Galbraith wrote:
> > 
> > > > Can you try the below, and send me 
> > > I tested it on Nehalem machine against the latest tips kernel. netperf loopback
> > > result is good and regression disappears.
> > 
> > Excellent.  Ingo has picked up a version in tip (1b9508f) which has zero
> > negative effect on my x264 testcase, and is a win for mysql+oltp through
> > the whole test spectrum.  As that may (dunno, Ingo?) now be considered a
> > regression fix, ie candidate for 32.final, testing that it does no harm
> > to your big machines would be a good thing.  (pretty please?:)
> I tested the latest tips kernel which includes commit 1b9508f.
> Comparing with 2.6.31, netperf loopback UDP-U-4k has about 2% regression.

Ok, thanks for testing.  That could well be a1f84a3, that needs a bit of
fiddling.

> sysbench(oltp)+mysql result is pretty good, about 2% improvement than
> 2.6.31's.

Cool, a progression for a change :)
 
> > > tbench result has no improvement.
> > 
> > Can you remind me where we stand on tbench?
> I run tbench by starting CPU_NUM*2 tbench clients without cpu binding.
> Comparing with 2.6.31, tbench has about 6% regression with 2.6.31-rc1 on Nehalem.
> Mostly, it's caused by SD_PREFER_LOCAL and Peter already disables the flag for
> MC and cpu domains. Your patch disables it for node domain.
> With the current tips kernel, tbench has about 3% regression on 1 nahalem, and
> less than 1% on another Nehalem.

Ok, we're not looking too bad, but still something there to go after.

> With pure 2.6.32-rc6 kernel, tbench result has about 3~6% regression on Nehalem
> , comparing with 2.6.32-rc5's. So some patches in tips haven't been merged into
> upstream.
 
> > > > your UDP-U-1k args so I can try it? 
> > > #taskset -c 0 ./netserver
> > > #taskset -c 15 ./netperf -t UDP_STREAM -l 60 -H 127.0.0.1 -i 50 3 -I 99 5 -- -P 12384,12888 -s 32768 -S 32768 -m 4096
> > > 
> > > Pls. check /proc/cpuinfo to make sure cpu 0 and cpu 15 are not in the
> > > same physical cpu.
> > 
> > Thanks. My little box doesn't have a 15 (darn) so 0,3 will have to do.
> Sorry. I copy it from the output of "ps -ef", so a couple of ',' are lost. The right netperf command
> line is:
> #taskset -c 15 ./netperf -t UDP_STREAM -l 60 -H 127.0.0.1 -i 50,3 -I 99,5 -- -P 12384,12888 -s 32768 -S 32768 -m 4096

Thanks.  (-i and -I have always given me trouble on my little boxen. I
usually just let it do it's thing without them, and repeat a lot;)

	-Mike

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