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Date: Tue, 25 Aug 2009 08:27:56 +1000
From: Paul Mackerras <paulus@samba.org>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: eranian@gmail.com, Ingo Molnar <mingo@elte.hu>,
       LKML <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>,
       Robert Richter <robert.richter@amd.com>,
       Andi Kleen <andi@firstfloor.org>, Maynard Johnson <mpjohn@us.ibm.com>,
       Carl Love <cel@us.ibm.com>, Corey J Ashford <cjashfor@us.ibm.com>,
       Philip Mucci <mucci@eecs.utk.edu>, Dan Terpstra <terpstra@eecs.utk.edu>,
       perfmon2-devel <perfmon2-devel@lists.sourceforge.net>
Subject: Re: perf_counters issue with enable_on_exec
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Peter Zijlstra writes:

> 2. enable_on_exec only works on leaders, Paul, was that intended?

I think I thought that would be sufficient, but I guess it would be
cleaner if it also worked on non-leaders.

> 3. the scale stuff seems broken
> 
> # perf stat -e cycles -e instructions --repeat 10 true
> 
>  Performance counter stats for 'true' (10 runs):
> 
>         2612124  cycles                     ( +-   1.327% )
>         1870479  instructions             #      0.716 IPC     ( +-   0.132% )
> 
>     0.003743155  seconds time elapsed   ( +-   1.203% )
> 
> # ./test-enable_on_exec true
>              2651600 PERF_COUNT_HW_CPU_CYCLES 1111509 1111509 2651600.000000
>              1832720 PERF_COUNT_HW_INSTRUCTIONS 839395242 1111509 1384043177.264637
> 
> Paul, would a counter's time start running when its 'enabled' but part
> of a non-runnable group?

No, it shouldn't.  If it does it's a bug.

Paul.