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

[Ingo Molnar]

* Jiri Olsa <jolsa@xxxxxxxxxx> 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

etc.

Is this how you implemented it?

If the threads in the thread pool are just free-running then the scheduler might 
not migrate it to the 'right' CPU that is streaming the perf events and there will 
be a lot of cross-talking between CPUs.

Inherited events (default 'perf record') is tougher.

Thanks,

	Ingo