linux-kernel - Re: [Perfctr-devel] [patch] Performance Counters for Linux, v4

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Message-ID: <494966E3.2020506@linux.vnet.ibm.com>
Date:	Wed, 17 Dec 2008 12:53:55 -0800
From:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>
To:	William Cohen <wcohen@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"David S. Miller" <davem@...emloft.net>,
	Robert Richter <robert.richter@....com>,
	Eric Dumazet <dada1@...mosbay.com>,
	Stephane Eranian <eranian@...glemail.com>,
	Paul Mackerras <paulus@...ba.org>, Peter Anvin <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	perfctr-devel@...ts.sourceforge.net,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [Perfctr-devel] [patch] Performance Counters for Linux, v4

William Cohen wrote:
> Ingo Molnar wrote:
>> We are pleased to announce the v4 release of our performance counters 
>> subsystem implementation. The kernel changes can be picked up from:
>>
>>    git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git 
>> perfcounters/core
>>
>>   (also in the master branch. There's also a kernel patch attached    
>> below.)
> 
> Machines that support virtualization are becoming very common.  How is
> this performance monitoring support going to work with virtualization
> (e.g. KVM)? Having the performance counters only work on physical
> machines would be pretty limiting.

On Power machines, the PMU counter registers are virtualized by the 
hypervisor, at the request of the OS, on a per-cpu/per-partition basis. 
  So this issue is handled transparently on Power anyway.

- Corey

Corey Ashford
Software Engineer
IBM Linux Technology Center, Linux Toolchain
Beaverton, OR
503-578-3507
cjashfor@...ibm.com

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