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


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