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From: Vince Weaver <vincent.weaver@maine.edu>
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Date: Fri, 20 Apr 2018 10:18:04 -0400 (EDT)
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To: Peter Zijlstra <peterz@infradead.org>
cc: Vince Weaver <vincent.weaver@maine.edu>, Jiri Olsa <jolsa@redhat.com>,
        Stephane Eranian <eranian@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Arnaldo Carvalho de Melo <acme@redhat.com>, mingo@elte.hu,
        Andi Kleen <ak@linux.intel.com>
Subject: Re: [RFC] perf/core: what is exclude_idle supposed to do
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On Fri, 20 Apr 2018, Peter Zijlstra wrote:

> On Wed, Apr 18, 2018 at 11:10:20AM -0400, Vince Weaver wrote:
> > On Tue, 17 Apr 2018, Jiri Olsa wrote:
> > 
> > > On Mon, Apr 16, 2018 at 10:04:53PM +0000, Stephane Eranian wrote:
> > > > Hi,
> > > > 
> > > > I am trying to understand what the exclude_idle event attribute is supposed
> > > > to accomplish.
> > > > As per the definition in the header file:
> > > > 
> > > >     exclude_idle   :  1, /* don't count when idle */
> > > 
> > > AFAICS it's not implemented
> > 
> > so just to be completely clear hear, we're saying that the "exclude_idle" 
> > modifier has never done anything useful and still doesn't?
> 
> AFAICT it works on Power and possibly ARM.

at least some ARMs are a bit more honest about it than x86

ivybridge:
	Performance counter stats for '/bin/ls':
	1,368,162      instructions
	1,368,162      instructions:I

pi2/ARM cortex-A7
	Performance counter stats for '/bin/ls':
	1,910,083      instructions
	<not supported>      instructions:I

I'd fire up my Power8 machine to see but not sure it's worth the hassle 
and/or having to get out the ear protection.

Vince