linux-kernel - Re: [Bug #10638] sysbench+mysql(oltp, readonly) 30% regression with 2.6.26-rc1

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Date:	Wed, 4 Jun 2008 13:19:51 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [Bug #10638] sysbench+mysql(oltp, readonly) 30% regression
	with 2.6.26-rc1

* Zhang, Yanmin <yanmin_zhang@...ux.intel.com> wrote:

> 
> On Fri, 2008-05-30 at 11:45 +0200, Ingo Molnar wrote:
> > Yanmin,
> > 
> > could you please check whether the performance regressions you 
> > noticed are now fixed in upstream -git? [make sure merge 
> > a7f75d3bed28 is included]
> > 
> > i believe most of the regressions to 2.6.25 you found should be 
> > addressed - if not, please let me know which one is still hurting.
>
> Most regressions are fixed.

great - thanks for the exhaustive testing! In fact there should be nice 
speedups in most of the categories as well ;-)

out of the 5 issues, only one is inconclusive:

> On 16-thread tulsa machine, hackbench result becomes 34 seconds. 
> 2.6.26-rc2's result is 40 seconds and 2.6.26-rc1's is 30 seconds. So 
> there is much improvement. On another Montvale machine(supporting 
> multi-threading, but I don't turn on it in BIOS), hackbench has the 
> similiar behavior.

okay, that's "hackbench 100", which creates a swarm of 2000 runnable 
tasks and which is extremely sensitive to wakeup preemption details. It 
is a volanomark work-alike, so if volanomark itself works fine (which it 
does appear, from your other numbers) and this one regresses a bit, i'm 
not sure there's anything fundamental to be worried about.

Quite likely you'll get more stable results if you run it all batched 
(which such workload really should):

 schedtool -B -e hackbench 100

right?

the 16-thread tulsa machine, how is it laid out physically: 2 sockets, 4 
cores per socket, 2 threads per core?

	Ingo
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