linux-kernel - Re: [PATCH 0/8] Add support for PowerPC Hypervisor supplied performance counters

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Date:	Wed, 22 Jan 2014 15:07:15 +0530
From:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:	Michael Ellerman <mpe@...erman.id.au>
CC:	Cody P Schafer <cody@...ux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Linux PPC <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH 0/8] Add support for PowerPC Hypervisor supplied performance
 counters

On 01/22/2014 07:02 AM, Michael Ellerman wrote:
> On Thu, 2014-01-16 at 15:53 -0800, Cody P Schafer wrote:
>> These patches add basic pmus for 2 powerpc hypervisor interfaces to obtain
>> performance counters: gpci ("get performance counter info") and 24x7.
>>
>> The counters supplied by these interfaces are continually counting and never
>> need to be (and cannot be) disabled or enabled. They additionally do not
>> generate any interrupts. This makes them in some regards similar to software
>> counters, and as a result their implimentation shares some common code (which
>> an initial patch exposes) with the sw counters.
> 
> Hi Cody,
> 
> Can you please add some more explanation of this series.
> 
> In particular why do we need two new PMUs, and how do they relate to each
> other?
> 
> And can you add an example of how I'd actually use them using perf.
> 

Yeah, agreed.

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