Re: [RFC/PATCHSET 00/14] perf report: Add support to accumulate hist periods (v2)

Namhyung Kim
2013-11-01T06:48:40Z

Hi Ingo,

On Thu, 31 Oct 2013 09:09:32 +0100, Ingo Molnar wrote:
> * Namhyung Kim <namhyung@kernel.org> wrote:
>
>> When the -g cumulative option is given, it'll be shown like this:
>>
>> $ perf report -g cumulative --stdio
>>
>> # Overhead Overhead (Acc) Command Shared Object Symbol
>> # ........ .............. ....... ................. .......................
>> #
>> 0.00% 88.29% abc libc-2.17.so [.] __libc_start_main
>> 0.00% 88.29% abc abc [.] main
>> 0.00% 88.29% abc abc [.] c
>> 0.00% 88.29% abc abc [.] b
>> 88.29% 88.29% abc abc [.] a
>> 0.00% 11.61% abc ld-2.17.so [k] _dl_sysdep_start
>> 0.00% 9.43% abc ld-2.17.so [.] dl_main
>> 9.43% 9.43% abc ld-2.17.so [.] _dl_relocate_object
>> 2.27% 2.27% abc [kernel.kallsyms] [k] page_fault
>> 0.00% 2.18% abc ld-2.17.so [k] _dl_start_user
>> 0.00% 0.10% abc ld-2.17.so [.] _start
>>
>> As you can see __libc_start_main -> main -> c -> b -> a callchain
>> show up in the output.
>
> This looks really useful!

Thanks! :)

>
> A couple of details:
>
> 1)
>
> This is pretty close to SysProf output, right? So why not use the
> well-known SysProf naming and call the first column 'self' and the
> second column 'total'? I think those names are pretty intuitive and
> it would help people who come from SysProf over to perf.

Okay, I can do it. (Although sysprof seems to call it 'cumulative'
rather than 'total' - but I think the 'total' is better since it's
simpler and shorter.)

>
> 2)
>
> Is it possible to configure the default 'report -g' style, so that
> people who'd like to use it all the time don't have to type '-g
> cumulative' all the time?

Hmm.. maybe I can add support for the 'report.call-graph' config option.

>
> 3)
>
> I'd even argue that we enable this reporting feature by default, if
> a data file includes call-chain data: the first column will still
> show the well-known percentage that perf report produces today, the
> second column will be a new feature in essence.
>
> The only open question would be, by which column should we sort:
> 'sysprof style' sorts by 'total', 'perf style' sorts by 'self'.
> Agreed?

Right, I defaulted to go by 'total'. But we can add an option for it.

>
> 4)
>
> This is not directly related to the new feature you added:
> call-graph profiling still takes quite a bit of time. It might make
> sense to save the ordered histogram to a perf.data.ordered file, so
> that repeat invocations of 'perf report' don't have to recalculate
> everything again and again?
>
> This file would be maintained transparently and would only be
> re-created when the perf.data file changes, or something like that.

Hmm.. good idea. We may discuss it along with Jiri's multiple file
storage patches. I haven't had a time to review - maybe next week.

>
> 5)
>
> I realize that this is an early RFC, still there are some usability
> complaints I have about call-graph recording/reporting which should
> be addressed before adding new features.
>
> For example I tried to get a list of the -g output modi via:
>
> $ perf report -g help
>
> Which produced a lot of options - I think it should produce only a
> list of -g options.

Right. I have a patchset for this. Will send it soon.

> It also doesn't list cumulative:
>
> -g, --call-graph <output_type,min_percent[,print_limit],call_order>
> Display callchains using output_type
> (graph, flat, fractal, or none) , min percent threshold, optional
> print limit, callchain order, key (function or address). Default:
> fractal,0.5,callee,function

Ah, I forgot to add it. Will fix!

>
> Also, the list is very long and not very readable - I think there
> should be more newlines.
>
> Then I tried to do:
>
> $ perf report -g
>
> which, somewhat surprisingly, was accepted. Given that call-graph
> perf.data is recognized automatically by 'perf report', the -g
> option should only accept -g <type> syntax and provide a list of
> options when '-g' or '-g help' is provided.

Will check.

>
> 6)
>
> A similar UI problem exists on the 'perf record' side: 'perf record
> --call-graph help' should produce a specific list of call-graph
> possibilities, not the two screens full output it does today.

Right. The patch will come soonish. :)

>
>> I know it have some rough edges or even bugs, but I really want to
>> release it and get reviews. It does not handle event groups and
>> annotations and it has a bug on TUI.
>>
>> You can also get this series on 'perf/cumulate-v2' branch in my tree at:
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
>
> So I tried it out on top of tip:master, with your testcase, and in
> the --stdio case it works very well:
>
> # Overhead Overhead (Acc) Command Shared Object Symbol
> # ........ .............. ....... ................. ..........................................
> #
> 0.00% 100.00% abc abc [.] _start
> 0.00% 100.00% abc libc-2.17.so [.] __libc_start_main
> 0.00% 100.00% abc abc [.] main
> 0.00% 100.00% abc abc [.] c
> 0.00% 100.00% abc abc [.] b
> 99.79% 100.00% abc abc [.] a
> 0.01% 0.21% abc [kernel.kallsyms] [k] apic_timer_interrupt
>
> In the TUI output the 'c' entry is not visible:
>
> 99.79% 100.00% abc abc [.] a
> 0.00% 99.79% abc abc [.] b
> 0.01% 0.21% abc [kernel.kallsyms] [k] apic_timer_interrupt
> 0.00% 0.19% abc [kernel.kallsyms] [k] smp_apic_timer_interrupt
>
> I suspect this is the 'TUI bug' you mentioned?

Exactly, I'll dig into it.

>
>> Any comments are welcome, thanks.
>
> Cool stuff, let's fix & merge it ASAP! :-)

hehe, Thanks!
Namhyung