linux-kernel - Re: [RFC] sched: CPU topology try

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Message-ID: <52CBD96B.4050103@linux.vnet.ibm.com>
Date:	Tue, 07 Jan 2014 16:09:39 +0530
From:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Vincent Guittot <vincent.guittot@...aro.org>,
	linux-kernel@...r.kernel.org, mingo@...nel.org, pjt@...gle.com,
	Morten.Rasmussen@....com, cmetcalf@...era.com, tony.luck@...el.com,
	alex.shi@...aro.org, linaro-kernel@...ts.linaro.org, rjw@...k.pl,
	paulmck@...ux.vnet.ibm.com, corbet@....net, tglx@...utronix.de,
	len.brown@...el.com, arjan@...ux.intel.com,
	amit.kucheria@...aro.org, james.hogan@...tec.com,
	schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
	Dietmar.Eggemann@....com
Subject: Re: [RFC] sched: CPU topology try

On 01/07/2014 03:20 PM, Peter Zijlstra wrote:
> On Tue, Jan 07, 2014 at 03:10:21PM +0530, Preeti U Murthy wrote:
>> What if we want to add arch specific flags to the NUMA domain? Currently
>> with Peter's patch:https://lkml.org/lkml/2013/11/5/239 and this patch,
>> the arch can modify the sd flags of the topology levels till just before
>> the NUMA domain. In sd_init_numa(), the flags for the NUMA domain get
>> initialized. We need to perhaps call into arch here to probe for
>> additional flags?
> 
> What are you thinking of? I was hoping all NUMA details were captured in
> the distance table.
> 
> Its far easier to talk of specifics in this case.
> 
If the processor can be core gated, then there is very little power
savings that we could yield from consolidating all the load onto a
single node in a NUMA domain. 6 cores on one node or 3 cores each on two
nodes, the power is drawn by 6 cores in all. So I was thinking under
this circumstance we might want to set the SD_SHARE_POWERDOMAIN flag at
the NUMA domain and spread the load if it favours the workload.

Regards
Preeti U Murthy

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