linux-kernel - Re: [PATCH v4] perf/x86/amd/power: Add AMD accumulated power reporting mechanism

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Message-ID: <20160128124209.GC14274@pd.tnic>
Date:	Thu, 28 Jan 2016 13:42:09 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Huang Rui <ray.huang@....com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Robert Richter <rric@...nel.org>,
	Jacob Shin <jacob.w.shin@...il.com>,
	John Stultz <john.stultz@...aro.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, spg_linux_kernel@....com,
	x86@...nel.org, Guenter Roeck <linux@...ck-us.net>,
	Andreas Herrmann <herrmann.der.user@...glemail.com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Aaron Lu <aaron.lu@...el.com>
Subject: Re: [PATCH v4] perf/x86/amd/power: Add AMD accumulated power
 reporting mechanism

On Thu, Jan 28, 2016 at 06:01:43PM +0800, Huang Rui wrote:
> For example: Carrizo has four CPU cores and two compute units (CUs).
> CPU0 and CPU1 belongs to CU0, CPU2 and CPU3 belongs to CU1.
> 
> At normal initialization, cpu_mask should be "0,2". That means OS
> choose CPU0 in CU0 and CPU2 in CU1 to measure the CU0 and CU1's power
> consumption. If we make the CPU2 offline at runtime, OS need try to
> find another CPU in same compute unit (Here is CU1, only CPU3 can be
> picked). Then OS will move on to the CPU3 to measure CU1's power
> consumption instead of CPU2.

So basically you want to simply say:

"Find another CPU on the same compute unit and set it in the mask of
CPUs on which we do the measurements."

Which reminds me: that cpu_mask thing is insufficiently named - it
should be called measuring_cpus_mask or so.

Btw, the kbuild robot errors come from the fact that there are changes
to cpufeature.h which I didn't mention when applying your patches. So
I've pushed the whole pile here:

http://git.kernel.org/cgit/linux/kernel/git/bp/bp.git/log/?h=tip-perf

Please use that branch instead.

Thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.