linux-kernel - Re: Re: [PATCH perf/core v3 3/3] [BUGFIX] perf probe: Show usage even if the last event is skipped

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Message-ID: <55818B0A.4030506@hitachi.com>
Date:	Wed, 17 Jun 2015 23:58:18 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
CC:	Naohiro Aota <naota@...sp.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>, namhyung@...nel.org,
	Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>
Subject: Re: Re: [PATCH perf/core v3 3/3] [BUGFIX] perf probe: Show usage
 even if the last event is skipped

On 2015/06/17 14:31, Masami Hiramatsu wrote:
>> > I.e. the only problem I found was this:
>> > 
>> > [root@zoo ~]# time perf probe -l > /dev/null
>> > 
>> > real	0m15.408s
>> > user	0m14.892s
>> > sys	0m0.534s
>> > [root@zoo ~]# 
>> > [root@zoo ~]# perf stat perf probe -l > /dev/null
>> > 
>> >  Performance counter stats for 'perf probe -l':
>> > 
>> >       15256.588897      task-clock (msec)         #    1.001 CPUs utilized          
>> >                116      context-switches          #    0.008 K/sec                  
>> >                  4      cpu-migrations            #    0.000 K/sec                  
>> >            230,720      page-faults               #    0.015 M/sec                  
>> >     47,830,405,530      cycles                    #    3.135 GHz                    
>> >     43,974,134,505      stalled-cycles-frontend   #   91.94% frontend cycles idle   
>> >    <not supported>      stalled-cycles-backend   
>> >     11,540,587,038      instructions              #    0.24  insns per cycle        
>> >                                                   #    3.81  stalled cycles per insn
>> >      2,807,769,592      branches                  #  184.037 M/sec                  
>> >         20,087,075      branch-misses             #    0.72% of all branches        
>> > 
>> >       15.240796324 seconds time elapsed
>> > 
>> > [root@zoo ~]#
>> > 
>> > Can you check why it takes so long and check the need for this patch?
> It is because perf probe -l is not optimized to show a lot of probes yet.
> It initializes and loads debuginfo for each probe. I guess we can reuse
> debuginfo among them. let me try...
> 

OK, I've ensured that's true,

[root@...alhost perf]# time  ./perf probe -l &> /dev/null

real    0m25.376s
user    0m24.381s
sys     0m1.012s

[root@...alhost perf]# time  ./perf probe --no-dwarf -l &> /dev/null

real    0m0.059s
user    0m0.039s
sys     0m0.020s

(Note that --no-dwarf is my local patch for debugging, not sending yet)

So, the problem is on the debuginfo processing. I've also fixed that
by caching the last used debuginfo. :)

[root@...alhost perf]#  time  ./perf probe -l &> /dev/null

real    0m0.161s
user    0m0.136s
sys     0m0.025s

I'll send the patch asap.

Thank you!

-- 
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@...achi.com
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