Date:	Thu, 05 Nov 2009 15:44:23 +0800
From:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
To:	Mike Galbraith <efault@....de>
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 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.

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



> 
> > 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.

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


> 
> > I also run sysbench(oltp)+mysql testing with thread number 14,16,18,20,32,64,128. The average
> > number is good. If I compare every single result against 2.6.32-rc5's, I find thread number
> > 14,16,18,20,32's result are better than 2.6.32-rc5's, but 64,128's result are worse. 128's is
> > the worst.
> 
> Hm.  That's disconcerting.  However, that patch isn't going anywhere but
> to the bitwolf anyway (diagnostic).  If 1b9508f regresses, that will be
> a problem.  With diag, my box also regressed at the tail.  Balancing a
> bit seems to help mysql once it starts tripping all over itself, it
> improves the decay curve markedly.  1b9508f does brief bursts of newidle
> balancing when idle time climbs, which translated to a ~6% improvement
> at 256 clients on my little quad.
> 
> 	-Mike
> 

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