Re: Mainline kernel OLTP performance update

Andrew Morton
2009-01-15T17:44:42Z

On Thu, 15 Jan 2009 09:12:46 -0500 James Bottomley <James.Bottomley@HansenPartnership.com> wrote:

> On Wed, 2009-01-14 at 18:04 -0800, Andrew Morton wrote:
> > On Wed, 14 Jan 2009 18:21:47 -0700 Matthew Wilcox <matthew@wil.cx> wrote:
> > > On Wed, Jan 14, 2009 at 04:35:57PM -0800, Andrew Morton wrote:
> > > > > > Linux OLTP Performance summary
> > > > > > Kernel# Speedup(x) Intr/s CtxSw/s us% sys% idle% iowait%
> > > > > > 2.6.24.2 1.000 21969 43425 76 24 0 0
> > > > > > 2.6.27.2 0.973 30402 43523 74 25 0 1
> > > > > > 2.6.29-rc1 0.965 30331 41970 74 26 0 0
> > >
> > > > But the interrupt rate went through the roof.
> > >
> > > Yes. I forget why that was; I'll have to dig through my archives for
> > > that.
> >
> > Oh. I'd have thought that this alone could account for 3.5%.
>
> Me too. Anecdotally, I haven't noticed this in my lab machines, but
> what I have noticed is on someone else's laptop (a hyperthreaded atom)
> that I was trying to demo powertop on was that IPI reschedule interrupts
> seem to be out of control ... they were ticking over at a really high
> rate and preventing the CPU from spending much time in the low C and P
> states. To me this implicates some scheduler problem since that's the
> primary producer of IPI reschedules ... I think it wouldn't be a
> significant extrapolation to predict that the scheduler might be the
> cause of the above problem as well.
>

Good point.

The context switch rate actually went down a bit.

I wonder if the Intel test people have records of /proc/interrupts for
the various kernel versions.