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

[Namhyung Kim]

Hi Ingo,

On Thu, 31 Oct 2013 09:09:32 +0100, Ingo Molnar wrote:
> * Namhyung Kim <namhyung@xxxxxxxxxx> 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
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