Re: [PATCH V3 0/6] event synthesization multithreading for perf record

[Namhyung Kim <namhyung@kernel.org>]

Hi Ingo,

On Tue, Oct 24, 2017 at 03:25:23PM +0200, Ingo Molnar wrote:
> 
> * Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
> 
> > Em Tue, Oct 24, 2017 at 02:59:44PM +0200, Ingo Molnar escreveu:
> > > 
> > > * Jiri Olsa <jolsa@redhat.com> wrote:
> > > 
> > > > I recently made some changes on threaded record, which are based
> > > > on Namhyungs time* API, which is needed to read/sort the data afterwards
> > > > 
> > > > but I wasn't able to get any substantial and constant reduce of LOST events
> > > > and then I got sidetracked and did not finish, but it's in here:
> > > 
> > > So, in the context of system-wide profiling, the way that would work best I think 
> > > is the following:
> > > 
> > >   thread #0 binds itself to CPU#0 (via sched_setaffinity) and creates a per-CPU event on CPU#0
> > >   thread #1 binds itself to CPU#1 (via sched_setaffinity) and creates a per-CPU event on CPU#1
> > >   thread #2 binds itself to CPU#2 (via sched_setaffinity) and creates a per-CPU event on CPU#2
> > 
> > Right, that is how I think it should be done as well, and those will
> > just dump on separate files, in a per session directory, with an extra
> > file for the session details, in what is now the header.
> 
> Yes. Also note how easy to examine such a directory structure is - I'd suggest 
> making all the session details textual eventually. I.e. only the ring-buffers 
> should be binary, the rest should be arch-independent text encoding.
> 
> It's also very extensible.

Agreed.

Also for multithread work, conversion to directory should be the first
step IMHO.

Thanks,
Namhyung


> 
> > Later, the same thing happens at processing time, this time we'll have
> > contention to access global thread state, the need for rounds of
> > PERF_SAMPLE_TIME based ordering, like what we have now in the
> > tools/perf/util/ordered-events.[ch] code, etc.
> > 
> > This works for both 'report', 'script', 'top', 'trace', etc, as is
> > basically the model we already have. All the work that was done for
> > refcounting the thread, map, etc as well as locking those rbtrees would
> > finally be taken full advantage of.
> 
> Yeah, cool!
> 
> Thanks,
> 
> 	Ingo