linux-kernel - Re: [PATCH v4 2/5] sched: Record the current active power savings level

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Date:	Mon, 24 Aug 2009 18:09:25 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Gautham R Shenoy <ego@...ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	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 v4 2/5] sched: Record the current active power savings
 level

On Tue, 2009-03-31 at 16:20 +0530, Gautham R Shenoy wrote:
> The existing load balancer code is dependent on the sched_mc_power_savings
> variable. However, on multi-core + multi-threaded machines, these decisions
> need to be dependent on the values of both sched_mc_power_savings and
> sched_smt_power_savings.
> 
> Create a new variable named active_power_savings_level which is the
> maximum of the sched_mc_power_savings and sched_smt_power_savings.
> 
> Record this value in a read mostly global variable at the time when the user
> changes the value of sched_mc/smt_power_savings tunable, and use it for
> load-balancing decisions instead of computing it everytime.

OK, so why keep these variables separate at all?

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