Hi Kor,

hpx::parallel::execution::parallel_executor::post is what eventually gets 
called if you use hpx::apply (or future::then) to create tasks. post itself 
should not take up much time, even in extreme cases. It's hard to say for sure 
without more information about your application but there are at least a few 
possibilities:


  1.  You haven't annotated your tasks and your tasks end up with the default 
name set by the executor. Have you annotated your tasks and do you see them at 
all in your traces?
  2.  You have annotated your tasks and we haven't fixed the annotations for 
all use cases. Are you actually using actions or just plain local functions? 
hpx::apply or hpx::async?
  3.  Your task size is too small for our overheads. What is a typical task 
size in your case? We typically recommend a task size of at least 1 ms to be on 
the safe side, but you can most likely go a bit smaller than that, especially 
if you don't have too many cores on your machine. I think if this were the case 
the symptoms would be a bit different though, so it's most likely not this.

Mikael
________________________________
From: [email protected] 
<[email protected]> on behalf of Jong, K. de (Kor) 
<[email protected]>
Sent: Tuesday, December 17, 2019 4:14:51 PM
To: [email protected]
Subject: [hpx-users] parallel_executor::post dominating APEX trace

Hi list,

I am using HPX commit bbc3ad7 (1.4.0-rc2 + APEX linking fix) and APEX to
gain insights into the run time behavior of my program (and hopefully
improve it, based on that). The trace I am looking at shows that by far
most of the time is spent by

hpx::parallel::execution::parallel_executor::post

instead of in my actions. Maybe this makes complete sense. Can someone
maybe explain in what situations parallel_executor::post would take up a
lot of time?

Thanks!

Kor
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