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

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Date:   Fri, 10 Feb 2017 18:14:43 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ingo Molnar <mingo@...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)

Hi Ingo,

On Fri, Feb 10, 2017 at 08:41:11AM +0100, Ingo Molnar wrote:
> 
> * 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.

Thanks!

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

The patch 4 makes it default.

By the way, the current default (sort by baseline) looks like below:

  $ perf diff | 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
     2.40%   +0.95%  [kernel.kallsyms]  [k] bit_putcs
     1.35%   -0.71%  [kernel.kallsyms]  [k] smp_call_function_single
     0.62%   +1.23%  [kernel.kallsyms]  [k] mutex_lock
     0.31%   +0.79%  [kernel.kallsyms]  [k] link_path_walk
     0.16%   +0.45%  [kernel.kallsyms]  [k] menu_select
     0.00%   +0.57%  [kernel.kallsyms]  [k] __rcu_read_unlock

While this example doesn't show much difference, it could be..

Thanks,
Namhyung