linux-kernel - Re: [PATCH v2 1/2] sched: Nominate idle load balancer from a semi-idle package.

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Message-ID: <87hc16kyk5.fsf@basil.nowhere.org>
Date:	Fri, 03 Apr 2009 09:04:42 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Gautham R Shenoy <ego@...ibm.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	"Balbir Singh" <balbir@...ibm.com>
Subject: Re: [PATCH v2 1/2] sched: Nominate idle load balancer from a semi-idle package.

Gautham R Shenoy <ego@...ibm.com> writes:
>
> Improve the algorithm to nominate the idle load balancer from a semi idle
> cores/packages thereby increasing the probability of the cores/packages being
> in deeper sleep states for longer duration.

The basic patch looks good.

In theory you could also look for a nearby nohz balancer in the end
to optimize traffic on the interconnect of a larger NUMA system, 
but it's probably not worth it.

>
> The algorithm is activated only when sched_mc/smt_power_savings != 0.

But it seems to me that this check could be dropped and doing it
unconditionally, because idle balancing doesn't need much memory
bandwith or cpu power, so always putting it nearby is good.

-Ani

-- 
ak@...ux.intel.com -- Speaking for myself only.
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