Re: Mainline kernel OLTP performance update

[Andrew Morton <akpm@linux-foundation.org>]

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?