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Message-ID: <1347684137.4340.166.camel@marge.simpson.net>
Date: Sat, 15 Sep 2012 06:42:17 +0200
From: Mike Galbraith <efault@....de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andreas Herrmann <andreas.herrmann3@....com>,
Nikolay Ulyanitsky <lystor@...il.com>,
Borislav Petkov <bp@...en8.de>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Subject: Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to
3.6-rc5 on AMD chipsets - bisected
On Fri, 2012-09-14 at 21:15 -0700, Linus Torvalds wrote:
> We don't do random crazy "use another scheduler" to hide problems with
> the default one.
I was proposing a diagnostic.
>
> And since you are the author of the regressing patch, and don't seem
> to treat the regression as something serious, I really see no
> alternative to just reverting it.
Wow, I don't know how you obtained that impression, but fine, nuke it.
> Linus
>
> On Sep 14, 2012 9:11 PM, "Mike Galbraith" <efault@....de> wrote:
> On Fri, 2012-09-14 at 23:27 +0200, Borislav Petkov wrote:
> > (Adding everybody to CC and leaving the below for
> reference.)
> >
> > Guys,
> >
> > as Nikolay says below, we have a regression in 3.6 with
> pgbench's
> > benchmark in postgresql.
> >
> > I was able to reproduce it on another box here and did a
> bisection run.
> > It pointed to the commit below.
> >
> > And yes, reverting that commit fixes the issue here.
>
> My wild (and only) theory is that this is userspace spinlock
> related.
> If so, starting the server and benchmark SCHED_BATCH should
> not only
> kill the regression, but likely improve throughput as well.
>
> -Mike
>
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