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SubjectRe: [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@kernel.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

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