linux-kernel - Re: perf: h/w counters not counted and no error/info reported to user

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Date:	Mon, 30 May 2011 10:22:05 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	David Ahern <dsahern@...il.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: perf: h/w counters not counted and no error/info reported to user


* David Ahern <dsahern@...il.com> wrote:

> 
> 
> On 05/27/2011 03:50 AM, Ingo Molnar wrote:
> > 
> > * David Ahern <dsahern@...il.com> wrote:
> > 
> >> By default (tip-perf-core) perf-stat enables a number of H/W counters:
> >>
> >> perf stat  -- sleep 1
> > 
> > did you mean to do 'perf stat -a sleep 1' ?
> 
> Adding the -a has its own problems. It blocks reading from fd=0 
> (stdin); I have to type Ctrl-D to see the results. The FD array 
> gets initialized to 0 and some case is not erroring out or setting 
> the fd.

Ok, that's a bug (and you sent the fix for it already) - weird that i 
havent seen this before, i use perf stat -a sleep 1 type of analysis 
all the time.

Thanks,

	Ingo
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