Re: [PATCH] Perf: bug fix: distinguish between rename and exec

[Arnaldo Carvalho de Melo <acme@ghostprotocols.net>]

Em Wed, Feb 15, 2012 at 01:48:33PM +0100, Peter Zijlstra escreveu:
> I really dislike changing generic code purely for the purpose of
> instrumentation like this. Better to pull perf_event_comm() out of here
> if you want to change semantics.
> 
> Personally I couldn't care less about renames, I think they're a waste
> of time, so I'm ok with the simple patch moving the perf_event_comm()
> into setup_new_exec() and possibly renaming it to perf_event_exec().
> 
> Acme, do you care about renames?

I like your idea of keeping the semantics of PERF_RECORD_COMM and
introducing a PERF_RECORD_EXEC, just have to think about how to handle
that in a way that the tools detect that we have PERF_RECORD_EXEC...

Humm, will be yet another fallback for setting an perf_event_attr bit,
just like with .sample_id_all and .exclude_{guest,host}...

That together with the per class errnos + __strerror() method will allow
to move all the event creation finally to perf_evlist__open() where all
this gets nicely hidden away from poor tools.

We can then even have an ui__evlist_perror() method that does all the
ui__warning calls, etc.

So, yes, from a tooling perspective, I want to be notified of renames
and being able to stop relying on PERF_RECORD_COMM to call
map_groups__flush and instead do it at PERF_RECORD_EXEC seems a
bonus.

- Arnaldo