linux-kernel - Re: [PATCH v10 10/11] sched: add SD_PREFER

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Date:	Thu, 26 Mar 2015 17:33:34 +0530
From:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Vincent Guittot <vincent.guittot@...aro.org>
CC:	mingo@...nel.org, linux-kernel@...r.kernel.org,
	Morten.Rasmussen@....com, kamalesh@...ux.vnet.ibm.com,
	riel@...hat.com, efault@....de, nicolas.pitre@...aro.org,
	dietmar.eggemann@....com, linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH v10 10/11] sched: add SD_PREFER_SIBLING for SMT level

On 03/26/2015 04:25 PM, Peter Zijlstra wrote:
> On Fri, Feb 27, 2015 at 04:54:13PM +0100, Vincent Guittot wrote:
>> Add the SD_PREFER_SIBLING flag for SMT level in order to ensure that
>> the scheduler will put at least 1 task per core.
>>
>> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
>> Reviewed-by: Preeti U. Murthy <preeti@...ux.vnet.ibm.com>
> 
> Preeti, what benchmarks did you use on power8 smt to verify performance?
> 
> I'm seeing a slight but statistically significant regression on my
> ivb-ep kernel build when I match the build concurrency to my core count.
> 
> /me goes run (and install, its a fairly new box) more benches.

I use ebizzy benchmark to test performance regressions. But for this
particular patch, I recollect that I did a code walk through to verify
the correctness of the patch and not a performance test. Let me run
ebizzy against this patch and verify.

Regards
Preeti U Murthy
> 

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