Date: Wed, 29 Apr 2009 09:07:06 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: "Styner, Douglas W" <douglas.w.styner@intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "Tripathi, Sharad C" <sharad.c.tripathi@intel.com>,
       "arjan@linux.intel.com" <arjan@linux.intel.com>,
       "Wilcox, Matthew R" <matthew.r.wilcox@intel.com>,
       "Kleen, Andi" <andi.kleen@intel.com>,
       "Siddha, Suresh B" <suresh.b.siddha@intel.com>,
       "Ma, Chinang" <chinang.ma@intel.com>,
       "Wang, Peter Xihong" <peter.xihong.wang@intel.com>,
       "Nueckel, Hubert" <hubert.nueckel@intel.com>,
       "Recalde, Luis F" <luis.f.recalde@intel.com>,
       "Nelson, Doug" <doug.nelson@intel.com>,
       "Cheng, Wu-sun" <wu-sun.cheng@intel.com>,
       "Prickett, Terry O" <terry.o.prickett@intel.com>,
       "Shunmuganathan, Rajalakshmi" <rajalakshmi.shunmuganathan@intel.com>,
       "Garg, Anil K" <anil.k.garg@intel.com>,
       "Chilukuri, Harita" <harita.chilukuri@intel.com>,
       "chris.mason@oracle.com" <chris.mason@oracle.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: Mainline kernel OLTP performance update
Message-Id: <20090429090706.bc5f462f.akpm@linux-foundation.org>
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On Wed, 29 Apr 2009 08:48:19 -0700 "Styner, Douglas W" <douglas.w.styner@intel.com> wrote:

> >-----Original Message-----
> >From: Andrew Morton [mailto:akpm@linux-foundation.org]
> >Sent: Wednesday, April 29, 2009 12:30 AM
> >To: Styner, Douglas W
> >Cc: linux-kernel@vger.kernel.org; Tripathi, Sharad C;
> >arjan@linux.intel.com; Wilcox, Matthew R; Kleen, Andi; Siddha, Suresh B;
> >Ma, Chinang; Wang, Peter Xihong; Nueckel, Hubert; Recalde, Luis F; Nelson,
> >Doug; Cheng, Wu-sun; Prickett, Terry O; Shunmuganathan, Rajalakshmi; Garg,
> >Anil K; Chilukuri, Harita; chris.mason@oracle.com
> >Subject: Re: Mainline kernel OLTP performance update
> >
> >On Tue, 28 Apr 2009 10:08:22 -0700 "Styner, Douglas W"
> ><douglas.w.styner@intel.com> wrote:
> >
> >> Summary: Measured the mainline kernel from kernel.org (2.6.30-rc3).
> >>
> >> The regression for 2.6.30-rc3 against the baseline, 2.6.24.2 is 1.91%.
> >Oprofile reports 71.1626% user, 28.8295% system.
> >>
> >> Linux OLTP Performance summary
> >> Kernel#            Speedup(x)   Intr/s  CtxSw/s us%     sys%    idle%
> >iowait%
> >> 2.6.24.2                1.000   22106   43709   75      24      0       0
> >> 2.6.30-rc3              0.981   30645   43027   75      25      0       0
> >
> >The main difference there is the interrupt frequency.  Do we know which
> >interrupt source(s) caused this?
>
> Our analysis of the interrupts shows that rescheduling interrupts are
> up 2.2x from 2.6.24.2 --> 2.6.30-rc3.  Qla2xxx interrupts are roughly
> the same.

(top-posting repaired)

OK, thanks.  Seems odd that the rescheduling interrupt rate increased
while the context-switch rate actually fell a couple of percent.

This came up a few weeks ago and iirc Peter was mainly involved, and I
don't believe that anything conclusive ended up happening.  Peter,
could you please remind us of (and summarise) the story here?

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