[argobots-discuss] Argobots ABT_eventual_set too slow

[Balaji, Pavan]

Hi Houjun,

> On Apr 25, 2019, at 3:19 PM, Houjun Tang <htang4 at lbl.gov> wrote:
> I have tried different things as you suggested, and it seems setting OMP_PROC_BIND=false (previously it is set to "spread") can solve the problem. With that variable set, ABT_eventual_set() takes similar time (under 0.00001 seconds) to when OpenMP is disabled. So maybe it's because the Argobots threads and OpenMP threads are executing on the same core and causes the slowdown?

That's a good find.  Yes, it looks like the OpenMP runtime is forcing the pthread to a specific core, so any child threads created by that thread would also be bound to the same core.

Presumably the argobots thread and execution stream are under your control.  Can you unset the binding in your execution stream when you create it?  You can use pthread_setaffinity_np, although that needs to be executed inside your ULT.

  -- Pavan