linux-kernel - Re: [PATCH v6 2/2] perf/x86/amd/power: Add AMD accumulated power reporting mechanism

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Date:	Thu, 3 Mar 2016 18:57:53 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Huang Rui <ray.huang@....com>
cc:	Borislav Petkov <bp@...e.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Robert Richter <rric@...nel.org>,
	Jacob Shin <jacob.w.shin@...il.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Kan Liang <kan.liang@...el.com>, linux-kernel@...r.kernel.org,
	spg_linux_kernel@....com, x86@...nel.org,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>,
	Borislav Petkov <bp@...en8.de>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH v6 2/2] perf/x86/amd/power: Add AMD accumulated power
 reporting mechanism

On Fri, 4 Mar 2016, Huang Rui wrote:
> On Thu, Mar 03, 2016 at 04:26:46PM +0100, Thomas Gleixner wrote:
> > Why? You do a full for_each_online_cpu(i) loop after that, which does
> > exactly the same thing, right?
> >  
> 
> But looks like power_cpu_init cannot handle it if we don't take any
> action here.
> 
> e. g. 
> cpu_mask: 0000 and online mask: 1111 -> power_cpu_init(0) -> cpu_mask is still: 0000
> 
> topology_sibling_cpumask(0): 0011
> target: 1 (i. e. we cannot do cpumask_set_cpu(0, &cpu_mask))

Fair enough, but then you don't need the power_cpu_init() call at all.

But your loop does not cover anything beyond the first socket. So you need a
separate init function which does:

   for_each_online_cpu(cpu) {
   	target = cpumask_first(topology_sibling_cpumask(cpu));
	if (!cpumask_test_cpu(target, cpumask))
	   	cpumask_set_cpu(target, cpumask);
   }	      
	   	
Thanks,

	tglx