linux-kernel - Re: [PATCHSET 0/4] perf diff: Introduce delta-abs compute method (v2)

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Date:   Fri, 10 Feb 2017 08:41:11 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHSET 0/4] perf diff: Introduce delta-abs compute method (v2)


* Namhyung Kim <namhyung@...nel.org> wrote:

> Hello,
> 
> This patchset adds 'delta-abs' compute method to -c/--compute option.
> The 'delta-abs' is same as 'delta' but shows entries with bigger
> absolute delta first instead of sorting numerically.  This is only
> useful together with -o option.
> 
>  * v2 changes
>   - rebase onto acme/perf/core
>   - change default option to '-o 1 -c delta-abs'
> 
> 
> Below is default output (-c delta):
> 
>   $ perf diff -o 1 -c delta | grep -v ^# | head
>     42.22%   +4.97%  [kernel.kallsyms]  [k] cfb_imageblit
>      0.62%   +1.23%  [kernel.kallsyms]  [k] mutex_lock
>              +1.15%  [kernel.kallsyms]  [k] copy_user_generic_string
>      2.40%   +0.95%  [kernel.kallsyms]  [k] bit_putcs
>      0.31%   +0.79%  [kernel.kallsyms]  [k] link_path_walk
>              +0.64%  [kernel.kallsyms]  [k] kmem_cache_alloc
>      0.00%   +0.57%  [kernel.kallsyms]  [k] __rcu_read_unlock
>              +0.45%  [kernel.kallsyms]  [k] alloc_set_pte
>      0.16%   +0.45%  [kernel.kallsyms]  [k] menu_select
>              +0.41%  ld-2.24.so         [.] do_lookup_x
> 
> Now with 'delta-abs' it shows entries have bigger delta value either
> positive or negative.
> 
>   $ perf diff -o 1 -c delta-abs | grep -v ^# | head
>     42.22%   +4.97%  [kernel.kallsyms]  [k] cfb_imageblit
>     12.72%   -3.01%  [kernel.kallsyms]  [k] intel_idle
>      9.72%   -1.31%  [unknown]          [.] 0x0000000000411343
>      0.62%   +1.23%  [kernel.kallsyms]  [k] mutex_lock
>              +1.15%  [kernel.kallsyms]  [k] copy_user_generic_string
>      2.40%   +0.95%  [kernel.kallsyms]  [k] bit_putcs
>      0.31%   +0.79%  [kernel.kallsyms]  [k] link_path_walk
>      1.35%   -0.71%  [kernel.kallsyms]  [k] smp_call_function_single
>              +0.64%  [kernel.kallsyms]  [k] kmem_cache_alloc
>      0.00%   +0.57%  [kernel.kallsyms]  [k] __rcu_read_unlock

Nice!

BTW., to me the second output looks a lot more intuitive and useful than the 
default one.

Would it be possible to flip over the default to the 'most useful' options, and 
see whether anyone complains?

Thanks,

	Ingo