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Date: Wed, 26 Oct 2011 09:21:54 -0200
From: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
To: Deng-Cheng Zhu <dczhu@mips.com>
Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>
Subject: Re: [RFC PATCH 2/2] tools/perf: Make group_fd static and move its
 place in __perf_evsel__open()
Message-ID: <20111026112154.GC9467@ghostprotocols.net>
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Em Wed, Oct 26, 2011 at 09:18:28AM -0200, Arnaldo Carvalho de Melo escreveu:
> Em Wed, Oct 26, 2011 at 02:26:03PM +0800, Deng-Cheng Zhu escreveu:
> > With _only_ your patch applied, I tested with the following commands on
> > MIPS 74K (4 counters available in total):

> > perf stat -g -e
> > L1-dcache-load-misses,cycles,LLC-load-misses,iTLB-loads,instructions
> > find / >/dev/null

> > I tried to group up to 5 events in the hope of seeing NOSPC error. But
> > the command didn't fail and output:

> >  Performance counter stats for 'find /':

> >            9300823 L1-dcache-load-misses
> >      <not counted> cycles
> >      <not counted> LLC-load-misses
> >      <not counted> iTLB-loads
> >      <not counted> instructions

> >        8.463207591 seconds time elapsed

> > This is due to the event state check in validate_group() filtering out
> > the grouped events in OFF state. They are in OFF state because we are
> > running the command with the perf tool as opposed to attaching to an
> > existing task:

> > builtin-stat.c:create_perf_stat_counter():

> >         if (target_pid == -1 && target_tid == -1) {
> >                 attr->disabled = 1;
> >                 attr->enable_on_exec = 1;
> >         }
> 
> But they should be in OFF state only till the target program gets
> exec'ed, right?
>  
> > I suppose X86 has this issue too -- collect_events() in validate_group()
> > won't do real work in the bottom half of the function.
> 
> I'm testing that now.

[root@emilia ~]# perf stat -g -e L1-dcache-load-misses,cycles,LLC-load-misses,iTLB-loads,instructions find / >/dev/null

 Performance counter stats for 'find /':

       158,807,949 L1-dcache-load-misses                                       
     <not counted> cycles                  
     <not counted> LLC-load-misses         
     <not counted> iTLB-loads              
     <not counted> instructions            

     100.676645958 seconds time elapsed

[root@emilia ~]# 

Yeah, reading more code...

- Arnaldo