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Date: Thu, 5 Nov 2015 17:51:01 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Jiri Olsa <jolsa@kernel.org>
Cc: lkml <linux-kernel@vger.kernel.org>, David Ahern <dsahern@gmail.com>,
        Ingo Molnar <mingo@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        "Liang, Kan" <kan.liang@intel.com>
Subject: Re: [PATCH 02/25] perf stat record: Add record command
Message-ID: <20151105205101.GY13236@kernel.org>
References: <1446734469-11352-1-git-send-email-jolsa@kernel.org>
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Em Thu, Nov 05, 2015 at 03:40:46PM +0100, Jiri Olsa escreveu:
> Add 'perf stat record' command support. It creates simple
> (header only) perf.data file ATM.
> 
> The record command could be specified anywhere among stat
> options. All stat command options are valid for stat record
> command with '-o' option exception. If specified for record
> command it denotes the perf data file name.
> 
> Tested-by: Kan Liang <kan.liang@intel.com>
> Link: http://lkml.kernel.org/n/tip-0av5yfkwyywwgoiali88w4hi@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>

Still stopping here:

[acme@zoo linux]$ rm -f perf.data
[acme@zoo linux]$ perf stat record usleep 1

 Performance counter stats for 'usleep 1':

          0.621181      task-clock (msec)         #    0.455 CPUs utilized          
                 1      context-switches          #    0.002 M/sec                  
                 0      cpu-migrations            #    0.000 K/sec                  
                54      page-faults               #    0.087 M/sec                  
           917,006      cycles                    #    1.476 GHz                    
           611,746      stalled-cycles-frontend   #   66.71% frontend cycles idle   
   <not supported>      stalled-cycles-backend   
           654,410      instructions              #    0.71  insns per cycle        
                                                  #    0.93  stalled cycles per insn
           132,653      branches                  #  213.550 M/sec                  
             7,432      branch-misses             #    5.60% of all branches        

       0.001365369 seconds time elapsed

[acme@zoo linux]$ ls -la perf.data
-rw-------. 1 acme acme 1384 Nov  5 17:42 perf.data
[acme@zoo linux]$ perf evlist
WARNING: The perf.data file's data size field is 0 which is unexpected.
Was the 'perf record' command properly terminated?
non matching sample_type[acme@zoo linux]$ 

--------------------------------

When we pass one event it gets a bit better:

[acme@zoo linux]$ rm -f perf.data
[acme@zoo linux]$ perf stat -e cycles record usleep 1

 Performance counter stats for 'usleep 1':

         1,056,818      cycles                                                      

       0.000715850 seconds time elapsed

[acme@zoo linux]$ ls -la perf.data
-rw-------. 1 acme acme 232 Nov  5 17:44 perf.data
[acme@zoo linux]$ perf evlist
WARNING: The perf.data file's data size field is 0 which is unexpected.
Was the 'perf record' command properly terminated?
cycles
[acme@zoo linux]$

-----

In the second case it almost works, modulo that warning.

I think that what we need to achieve is for older tools to be able to, with a
file produced by 'perf stat record', to show this:

[root@zoo ~]# perf report --no-header --stdio
Error:
The perf.data file has no samples!
# To display the perf.data header info, please use --header/--header-only options.
#
[root@zoo ~]# 


I.e. the file should look like one that is produced by this command, purposely
to not create any sample:

# perf record -e syscalls:sys_enter_accept usleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.018 MB perf.data ]


I applied the first patch and added it to that perf/stat branch.

- Arnaldo
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