Messages in this thread | | | Date | Tue, 19 May 2015 21:22:10 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 35/40] perf record: Synthesize COMM event for a command line workload |
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Em Wed, May 20, 2015 at 08:56:58AM +0900, Namhyung Kim escreveu: > On Tue, May 19, 2015 at 05:18:54PM -0300, Arnaldo Carvalho de Melo wrote: > > Em Tue, May 19, 2015 at 09:49:03PM +0200, Jiri Olsa escreveu: > > > > > Humm, you're thinking about where you managed to reproduce the problem, > > > > > I am thinking outside indexing, etc, i.e. by definition we either enable > > > > > the event before we fork, so that we get the PERF_RECORD_FORK/COMM or we > > > > > synthesize it either from /proc or directly (preferred) if we decide to > > > > > do it after the fork/exec, right?
> > > > But as I said before, later COMM event will override thread->comm to a > > > > proper string as long as it can find a matching thread. So I think it > > > > has no problem in the current code.
> > > I can see the issue in the current script code and the patch cured it ;-)
> > Exactly, this is my point, this is not something new :-)
> Ah, okay. The perf script shows samples before processing comm events > while perf report shows after processing all events.
I.e. 'perf script' behaves like 'perf trace' and 'perf top'. 'perf report' is the odd one out, and I think it should be not, i.e. you should try to think more about the non 'report' use cases when thinking about how to improve report :-)
But I digress, lets get back to the question at hand...
> But to move it under generic place like perf_evlist__{prepare,start}_ > workload(), it seems we need to pass an additional callback and data.
Only if you want to do it with perf_event__synthesize_comm(). I suggested writing a new synthesize routine that doesn't parses /proc, as we have all that we need, no?
I think that just doing something like:
thread = machine__findnew_thread(evlist->workload.pid, evlist->workload.pid); if (thread) thread__set_comm(thread, argv[0], timestamp);
Should be enough, no? I.e. no need for setting up a PERF_RECORD_FORK and a PERF_RECORD_COMM, read /proc, etc, just do it directly with the info we used to do the fork in perf_evlist__prepare_workload(), etc.
> I'll try to write a patch.
Great!
- Arnaldo
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