linux-kernel - Re: [PATCH 3/3] PM: Introduce Intel PowerClamp Driver

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Message-ID: <50A2C21D.6070108@linux.intel.com>
Date:	Tue, 13 Nov 2012 13:56:45 -0800
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	paulmck@...ux.vnet.ibm.com
CC:	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	Linux PM <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Len Brown <len.brown@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Zhang Rui <rui.zhang@...el.com>, Rob Landley <rob@...dley.net>
Subject: Re: [PATCH 3/3] PM: Introduce Intel PowerClamp Driver

On 11/13/2012 1:16 PM, Paul E. McKenney wrote:
> On Mon, Nov 12, 2012 at 02:03:51PM -0800, Jacob Pan wrote:
>> Intel PowerClamp driver performs synchronized idle injection across
>> all online CPUs. The goal is to maintain a given package level C-state
>> ratio.
>>
>> Compared to other throttling methods already exist in the kernel,
>> such as ACPI PAD (taking CPUs offline) and clock modulation, this is often
>> more efficient in terms of performance per watt.
>>
>> Please refer to Documentation/thermal/intel_powerclamp.txt for more details.
> 
> If I read this correctly, this forces a group of CPUs into idle for
> about 600 milliseconds at a time.  This would indeed delay grace periods,

6ms not 600


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