Re: [PATCH 3/3] perf callchain: Prune misleading callchains for self entries

[Jiri Olsa <jolsa@redhat.com>]

On Thu, Aug 14, 2014 at 03:01:40PM +0900, Namhyung Kim wrote:

SNIP

> However, with --children feature added, it now can show all callees of
> the entry.  For example, "start_kernel" entry now can display it calls
> rest_init and in turn cpu_idle and then cpuidle_idle_call (95.72%).
> 
>      6.14%     0.00%  swapper          [kernel.kallsyms]   [k] start_kernel
>                    |
>                     --- start_kernel
>                         rest_init
>                         cpu_idle
>                        |
>                        |--97.52%-- cpuidle_idle_call
>                        |          cpuidle_enter_tk
>                        |          |
>                        |          |--99.91%-- cpuidle_wrap_enter
>                        |          |          cpuidle_enter
>                        |          |          intel_idle
>                        |           --0.09%-- [...]
>                         --2.48%-- [...]
> 
> Note that start_kernel has no self overhead - meaning that it never
> get sampled by itself but constructs such a nice callgraph.  But,
> sadly, if an entry has self overhead, callchain will get confused with
> generated callchain (like above) and self callchains (which reversed
> order) like the eariler example.
> 
> To be consistent with other entries, I'd like to make it just to show
> a single entry - itself - like below since it doesn't have callees
> (children) at all.  But still use the whole callchain to construct
> children entries (like the start_kernel) as usual.
> 
>     40.53%    40.53%  swapper          [kernel.kallsyms]   [k] intel_idle
>                     |
>                     --- intel_idle

I understand the consistency point, but I think we'd loose
usefull info by cutting this off

I guess I can run 'report -g callee' to find out who called intel_idle
instead.. but I would not need to if the callchain stays here

jirka