linux-kernel - Re: [PATCH v2 2/2] perf tools: Make Power7 events available for perf

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Date:	Thu, 11 Jul 2013 16:58:08 +1000
From:	Michael Ellerman <michael@...erman.id.au>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Vince Weaver <vince@...ter.net>,
	Runzhen Wang <runzhen@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	paulus@...ba.org, acme@...hat.com,
	Stephane Eranian <eranian@...gle.com>,
	sukadev@...ux.vnet.ibm.com, xiaoguangrong@...ux.vnet.ibm.com
Subject: Re: [PATCH v2 2/2] perf tools: Make Power7 events available for perf

On Thu, Jul 11, 2013 at 12:42:31AM -0400, Vince Weaver wrote:
> On Wed, 10 Jul 2013, Ingo Molnar wrote:
> 
> > Exactly - PMUs enumerated in /sys should be self-identifying, it's a 
> > hardware topology after all ...
> > 
> > Anytime userspace is forced to look into /proc, or into weird places in 
> > /sys it's a FAIL really.
> 
> well on x86 you have to look at /proc/cpuinfo to get the 
> vendor/family/model number.  Should we add some specifier under sys?
> It's probably too late though as all userspace event libs will have
> to look at /proc/cpuinfo anyway to be backwards compatible.

If it's a new library implementing a new feature then no I don't think
it needs to be backward compatible. It's just a choice the library makes
as to what extent it depends on new kernel features.

cheers
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