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SubjectRe: sched: Avoid SMT siblings in select_idle_sibling() if possible

* Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> wrote:

> * Mike Galbraith <efault@gmx.de> [2012-02-20 19:14:21]:
>
> > > I was looking at this code due to vatsa wanting to do SD_BALANCE_WAKE.
> >
> > I really really need to find time to do systematic mainline testing.
> >
> > Enabling SD_BALANCE_WAKE used to be decidedly too expensive to consider.
> > Maybe that has changed, but I doubt it. (general aside: testing with a
> > bloated distro config is a big mistake)
>
> I am seeing 2.6% _improvement_ in volanomark score by enabling SD_BALANCE_WAKE
> at SMT/MC domains.
>
> Machine : 2 Quad-core Intel X5570 CPU (H/T enabled)
> Kernel : tip (HEAD at 6241cc8)
> Java : OpenJDK 1.6.0_20
> Volano : 2_9_0
>
> Volano benchmark was run 4 times with and w/o SD_BALANCE_WAKE enabled in
> SMT/MC domains.
>
> Average score std. dev
>
> SD_BALANCE_WAKE disabled 369459.750 4825.046
> SD_BALANCE_WAKE enabled 379070.500 379070.5
>
> I am going to try pipe benchmark next. Do you have suggestions
> for any other benchmarks I should try to see the effect of
> SD_BALANCE_WAKE turned on in SMT/MC domains?

sysbench is one of the best ones punishing bad scheduler
balancing mistakes.

Thanks,

Ingo


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