linux-kernel - Re: [PATCH v4 0/5] tracing/hist: Add percentage histogram suffixes

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Date:   Wed, 31 Aug 2022 16:35:25 -0500
From:   Tom Zanussi <zanussi@...nel.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 0/5] tracing/hist: Add percentage histogram suffixes

Hi Masami,

On Sat, 2022-08-27 at 13:03 +0900, Masami Hiramatsu (Google) wrote:
> Hi,
> 
> Here is the 4th version of .percent and .graph suffixes for histogram
> trigger to show the value in percentage and in bar-graph
> respectively.
> 
> I've rebased on Tom's hitcount patch[1/5] on the series and added a
> patch
> for supressing display of hitcount[5/5] in this version.

This is a very nice patchset overall - the only question I have
concerns patch 5 for suppressing the hitcount.  I actually think the
patch is fine and does what it says nicely (and probably should have
been done that way to begin with) but it looks like it would cause
problems for anyone already doing postprocessing and whose scripts
would be expecting the hitcount to be there.  So changing the default
behavior would require their scripts to change, and also now that I
look at it, the example output in Documentation/ as well.

How about adding an option like 'nohitcount' and having that patch do
what it does but only if that option is set?

Anyway, for the other ones, patches 2-4,

  Signed-off-by: Tom Zanussi <zanussi@...nel.org>
  Tested-by: Tom Zanussi <zanussi@...nel.org

Thanks!

Tom

> 
> This will help us to check the trend of the histogram instantly
> without any post processing tool.
> 
> Here shows an example of the percentage and the bar graph of
> the hitcount of the running tasks.
> 
>   # cd /sys/kernel/debug/tracing/
>   # echo hist:keys=pid:vals=hitcount.percent,hitcount.graph:sort=pid
> > \
>         events/sched/sched_stat_runtime/trigger
>   # sleep 10
>   # cat events/sched/sched_stat_runtime/hist
>  # event histogram
>  #
>  # trigger info:
> hist:keys=pid:vals=hitcount.percent,hitcount.graph:sort=pid:size=2048
> [active]
>  #
> 
>  { pid:         14 } hitcount (%):   4.68  hitcount:
> ###                 
>  { pid:         16 } hitcount (%):  17.18  hitcount:
> ###########         
>  { pid:         57 } hitcount (%):   7.81  hitcount:
> #####               
>  { pid:         61 } hitcount (%):  31.25  hitcount:
> ####################
>  { pid:         70 } hitcount (%):   4.68  hitcount:
> ###                 
>  { pid:         77 } hitcount (%):   1.56  hitcount:
> #                   
>  { pid:        145 } hitcount (%):  18.75  hitcount:
> ############        
>  { pid:        151 } hitcount (%):   9.37  hitcount:
> ######              
>  { pid:        152 } hitcount (%):   4.68  hitcount:
> ###                 
> 
>  Totals:
>      Hits: 64
>      Entries: 9
>      Dropped: 0
> 
> Of course if you explicitly specify the hitcount, it can show the
> hitcount as below;
> 
>   # cd /sys/kernel/debug/tracing/
>   # echo hist:keys=pid:vals=hitcount,runtime:sort=pid > \
>         events/sched/sched_stat_runtime/trigger
>   # sleep 10
>   # cat events/sched/sched_stat_runtime/hist
>  # event histogram
>  #
>  # trigger info:
> hist:keys=pid:vals=hitcount,runtime:sort=pid:size=2048 [active]
>  #
> 
>  { pid:         14 } hitcount:          2  runtime:     304876
>  { pid:         16 } hitcount:          8  runtime:     300574
>  { pid:         26 } hitcount:          2  runtime:      15578
>  { pid:         32 } hitcount:          2  runtime:     219186
>  { pid:         57 } hitcount:          3  runtime:     506003
>  { pid:         61 } hitcount:         20  runtime:    1681473
>  { pid:         69 } hitcount:          3  runtime:     201785
>  { pid:         70 } hitcount:          4  runtime:     360608
>  { pid:         77 } hitcount:          8  runtime:    4146935
>  { pid:        145 } hitcount:         13  runtime:    7537994
>  { pid:        155 } hitcount:          4  runtime:    2511937
>  { pid:        156 } hitcount:          2  runtime:    1398886
> 
>  Totals:
>      Hits: 71
>      Entries: 12
>      Dropped: 0
> 
> 
> Thank you,
> 
> ---
> 
> Masami Hiramatsu (Google) (4):
>       tracing: Fix to check event_mutex is held while accessing
> trigger list
>       tracing: Add .percent suffix option to histogram values
>       tracing: Add .graph suffix option to histogram value
>       tracing: Show hitcount value only when specified
> 
> Tom Zanussi (1):
>       tracing: Allow multiple hitcount values in histograms
> 
> 
>  kernel/trace/trace.c                |    3 -
>  kernel/trace/trace_events_hist.c    |  176
> ++++++++++++++++++++++++++++++-----
>  kernel/trace/trace_events_trigger.c |    3 -
>  3 files changed, 156 insertions(+), 26 deletions(-)
> 
> --
> Masami Hiramatsu (Google) <mhiramat@...nel.org>