linux-kernel - Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to 3.6-rc5 on AMD chipsets

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Message-ID: <20120928123008.GA16372@x1.osrc.amd.com>
Date:	Fri, 28 Sep 2012 14:30:09 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Mike Galbraith <efault@....de>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>, Mel Gorman <mgorman@...e.de>,
	Nikolay Ulyanitsky <lystor@...il.com>,
	linux-kernel@...r.kernel.org,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to
 3.6-rc5 on AMD chipsets - bisected

On Fri, Sep 28, 2012 at 05:50:20AM +0200, Mike Galbraith wrote:
> And wakeup preemption is still disabled as well, correct?

Yes it is by default anyway:

$ cat /mnt/dbg/sched_features
GENTLE_FAIR_SLEEPERS START_DEBIT NO_NEXT_BUDDY LAST_BUDDY CACHE_HOT_BUDDY NO_WAKEUP_PREEMPTION ARCH_POWER NO_HRTICK NO_DOUBLE_TICK LB_BIAS OWNER_SPIN NONTASK_POWER TTWU_QUEUE NO_FORCE_SD_OVERLAP RT_RUNTIME_SHARE NO_LB_MIN

NO_WAKEUP_PREEMPTION brings 9% improvement with pgbench, btw:

http://marc.info/?l=linux-kernel&m=134876312310048

-- 
Regards/Gruss,
Boris.
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