linux-kernel - Re: [PATCH 2/2 v3] tracing/histogram: Update the documentation for the buckets modifier

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Date:   Thu, 08 Jul 2021 15:05:16 -0500
From:   Tom Zanussi <zanussi@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: [PATCH 2/2 v3] tracing/histogram: Update the documentation for
 the buckets modifier

Hi Steve,

On Wed, 2021-07-07 at 17:36 -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> 
> Update both the tracefs README file as well as the histogram.rst to
> include an explanation of what the buckets modifier is and how to use
> it.
> Include an example with the wakeup_latency example for both log2 and
> the
> buckets modifiers as there was no existing log2 example.
> 
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> ---
>  Documentation/trace/histogram.rst | 92
> +++++++++++++++++++++++++++++--
>  kernel/trace/trace.c              |  1 +
>  2 files changed, 87 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/trace/histogram.rst
> b/Documentation/trace/histogram.rst
> index b71e09f745c3..11094ec6e52e 100644
> --- a/Documentation/trace/histogram.rst
> +++ b/Documentation/trace/histogram.rst
> @@ -77,6 +77,7 @@ Documentation written by Tom Zanussi
>  	.syscall    display a syscall id as a system call name
>  	.execname   display a common_pid as a program name
>  	.log2       display log2 value rather than raw number
> +	.buckets=size  display grouping of values rather than raw
> number
>  	.usecs      display a common_timestamp in microseconds
>  	=========== ==========================================
>  
> @@ -228,7 +229,7 @@ Extended error information
>    that lists the total number of bytes requested for each function
> in
>    the kernel that made one or more calls to kmalloc::
>  
> -    # echo 'hist:key=call_site:val=bytes_req' > \
> +    # echo 'hist:key=call_site:val=bytes_req.buckets=32' > \
>              /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger

This just seems random, not sure why you changed it, and it doesn't
make sense on a val anyway..

The rest looks good, though, thanks for doing this!

Reviewed-by: Tom Zanussi <zanussi@...nel.org>