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

Masami Hiramatsu
2015-06-17T14:58:28Z

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@localhost perf]# time ./perf probe -l &> /dev/null

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

[root@localhost 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@localhost 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@hitachi.com