Re: volanoMark regression with kernel 2.6.26-rc1

Zhang, Yanmin
2008-05-08T06:08:53Z

On Wed, 2008-05-07 at 20:58 +0200, Peter Zijlstra wrote:
> On Wed, 2008-05-07 at 19:34 +0200, Peter Zijlstra wrote:
> > On Wed, 2008-05-07 at 11:17 +0200, Ingo Molnar wrote:
> > > * Zhang, Yanmin <yanmin_zhang@linux.intel.com> wrote:
> > >
> > > > Comparing with 2.6.25, volanoMark has big regression with kernel
> > > > 2.6.26-rc1. It's about 50% on my 8-core stoakley, 16-core tigerton,
> > > > and Itanium Montecito.
> > > >
> > > > With bisect, I located below patch.
> > >
> > > thanks Yanmin, i've queued up your patch that reverts this change.
> >
> > Is this really needed now that GROUP_SCHED defaults to 'n' ?
> >
> > Yanmin, this is with GROUP_SCHED=y, right or is this without?
>
> Its a long shot, but does the below help?
I tested it on 8-core stoakley. The result is equal to the one of pure 2.6.26-rc1.

>
> ---
> Subject: sched: fixup SMP load-balance
>
> Keeping the aggregate on the first cpu of the sched domain has two problems:
> - it could collide between different sched domains on different cpus
> - it could slow things down because of the remote accesses
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> ---
> include/linux/sched.h | 1
> kernel/sched.c | 113 +++++++++++++++++++++++---------------------------
> kernel/sched_fair.c | 12 ++---
> 3 files changed, 60 insertions(+), 66 deletions(-)