[patch] scheduler cache affinity improvement in 2.4 kernels by Ingo Molnar

[patch] scheduler cache affinity improvement in 2.4 kernels by Ingo Molnar

[Partha Narayanan]

Folks,


The above patch for scheduler cache affinity improvement in 2.4 kernels by
Ingo Molnar was applied to 2.4.14 kernel;
a run of Volano LoopBack BenchMark on a Netfinity 8500 R 1MB 700 MHz PIII
1MB-L2 cache and 1GB memory support produced
the following results:

     The UniProcessor throughput  was reduced by 40%.
     The 4-way throughput showed a very slight degradation of 1%.
     The 8-way throughput showed an improvemnet of 10%.


I do not subscribe to lkml and hence please address any future
correspondence on this topic to partha@us.ibm.,com.

Thanks,
Partha

Re: [patch] scheduler cache affinity improvement in 2.4 kernels by Ingo Molnar

[Mark Hahn]

>      The UniProcessor throughput  was reduced by 40%.
>      The 4-way throughput showed a very slight degradation of 1%.
>      The 8-way throughput showed an improvemnet of 10%.

what a waste of time: volanomark loopback is deliberately unlike
any real-world workload, so noone can sanely use these numbers.
why not compare to something vaguely intelligible?  even lmbench
would be more interesting...

Re: [patch] scheduler cache affinity improvement in 2.4 kernels by Ingo Molnar

[Alan Cox]

>      The UniProcessor throughput  was reduced by 40%.
>      The 4-way throughput showed a very slight degradation of 1%.
>      The 8-way throughput showed an improvemnet of 10%.

This is the 10 billion thread volcanomark stuff though I assume ? What
happens in the real world ?

Re: [patch] scheduler cache affinity improvement in 2.4 kernels by Ingo Molnar

[Arnaldo Carvalho de Melo]

Em Sat, Nov 17, 2001 at 06:00:37PM +0000, Alan Cox escreveu:
> >      The UniProcessor throughput  was reduced by 40%.
> >      The 4-way throughput showed a very slight degradation of 1%.
> >      The 8-way throughput showed an improvemnet of 10%.
> 
> This is the 10 billion thread volcanomark stuff though I assume ? What
> happens in the real world ?

Hey, those who need 10 billion threads can afford a 8-way machine or even
bigger ;)

- Arnaldo

``"90% of everything is crap", Its called Sturgeon's law 8)
One of the problems is indeed finding the good bits''
    - Alan Cox

Re: [patch] scheduler cache affinity improvement in 2.4 kernels by Ingo Molnar

[Albert D. Cahalan]

Partha Narayanan writes:

> The above patch for scheduler cache affinity improvement in 2.4 kernels by
> Ingo Molnar was applied to 2.4.14 kernel;

Just a thought: some processors tell you how many cache lines
have been thrown out. Look in whatever performance monitoring
registers are available.

Re: [patch] scheduler cache affinity improvement in 2.4 kernels by Ingo Molnar

[Ingo Molnar]

On Sat, 17 Nov 2001, Partha Narayanan wrote:

>      The UniProcessor throughput  was reduced by 40%.
>      The 4-way throughput showed a very slight degradation of 1%.
>      The 8-way throughput showed an improvemnet of 10%.

thanks Partha for the measurements. I'll soon post an updated patch that
also includes some of the suggestions from this list.

	Ingo

Re: [patch] scheduler cache affinity improvement in 2.4 kernels by Ingo Molnar

[Shailabh Nagar]

Hi Partha,

Sorry to see the "shoot-the-messenger" replies to your posting. I've yet to
understand why lmbench is relevant
in an SMP setting.....

Shailabh Nagar
Enterprise Linux Group, IBM TJ Watson Research Center
(914) 945 2851, T/L 862 2851


Partha Narayanan/Austin/IBM@IBMUS@vger.kernel.org on 11/17/2001 11:58:05 AM

Sent by:  linux-kernel-owner@vger.kernel.org


To:   linux-kernel@vger.kernel.org
cc:
Subject:  [patch] scheduler cache affinity improvement in 2.4 kernels by
      Ingo Molnar



Folks,


The above patch for scheduler cache affinity improvement in 2.4 kernels by
Ingo Molnar was applied to 2.4.14 kernel;
a run of Volano LoopBack BenchMark on a Netfinity 8500 R 1MB 700 MHz PIII
1MB-L2 cache and 1GB memory support produced
the following results:

     The UniProcessor throughput  was reduced by 40%.
     The 4-way throughput showed a very slight degradation of 1%.
     The 8-way throughput showed an improvemnet of 10%.


I do not subscribe to lkml and hence please address any future
correspondence on this topic to partha@us.ibm.,com.

Thanks,
Partha


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Re: [patch] scheduler cache affinity improvement in 2.4 kernels by Ingo Molnar

[Samium Gromoff]

           So as i see the patch in question is being hit in its weakest
    place by that enormous 10 billion thread benchmark. 
    Indeed that weakest place is the added overhead which effects the
    heavy scheduling load.
      I look at it as at absolutely worst case. And even in this worst
    case we still have a win on a 8-way smp... I`d like to see some
    more real-life benchmarks on the issue...

      Maybe the tester lose the point, cause the patch was not pointed
   to improve the scheduling itself, but to reduce the loss of improper
   scheduling - ie cache thrashing.


cheers, Samium Gromoff