Re: [PATCH] perf: Add a new sort order: SORT_INCLUSIVE (v4)

[Arun Sharma]

On 3/19/12 8:57 AM, Frederic Weisbecker wrote:

> > > Each hist have a period of 1, but the total period is 1.
> > > So the end result should be (IIUC):
> > >
> > > 100%    foo     a
> > > 100%    foo     b
> > >                  |
> > >                  --- a
> > > 100%    foo     c
> > >                  |
> > >                  --- b
> > >                      |
> > >                      --- c
> >
> > That is correct. The first column no longer adds up to 100%.
>
> So do we really want this?

I think so. It's a different way of presenting the data. Pie chart vs a 
bar chart of OS market share where people may be using more than one OS.

I'll post some documentation updates.

> > If we don't do this, total_period will be inflated.
>
> Yeah right I've just tried and callchains look right. I'm just puzzled
> by the percentages:

Thanks for testing this!

> +  98,99%  [k] execve
> +  98,99%  [k] stub_execve
> +  98,99%  [k] do_execve
> +  98,99%  [k] do_execve_common
> +  98,99%  [k] sys_execve
> +  53,12%  [k] __libc_start_main
> +  53,12%  [k] cmd_record

These look like they belong to the perf binary and are incorrectly 
classified as kernel samples. Problem is that callchain_get() is not 
populating the privilege level - it's simply propagating the privilege 
level of the sample:


+       for (i = 0; i < cursor->nr; i++) {
+               struct addr_location al_child = *al;
+
+               err = callchain_get(&iter, &al_child);

Not all fields of al_child are populated by callchain_get().

> +  53,12%  [k] T.101
> +  53,12%  [k] main
> +  53,12%  [k] run_builtin
> +  52,11%  [k] perf_evlist__prepare_workload
> +  52,09%  [k] T.1163

The rest of them look ok to me. If something doesn't make sense, please 
point me at the output of "perf script".

> > > Also this feature reminds me a lot the -b option in perf report.
> > > Branch sorting and callchain inclusive sorting are a bit different in
> > > the way they handle the things but the core idea is the same. Callchains
> > > are branches as well.
> >
> > Yes - I kept asking why the branch stack stuff doesn't use the
> > existing callchain logic.
>
> Because I fear that loops branches could make the tree representation useless.

The loops could happen in callgraphs too right (eg: recursive programs)? 
The other problem in branch stacks/LBR is that they're sampled branches. 
Just because I got a sample with:

a -> b
b -> c

doesn't necessarily mean that the callchain was a -> b -> c.

I still don't have the branch stack setup working properly. But I'm now 
more sympathetic to the view that last branch sampling and callchains 
may have different representations in perf.

 -Arun
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