Re: How to share asyn's queue thread among ports?

["Konrad, Martin via Tech-talk" <tech-talk@aps.anl.gov>]

Hi Klemen,
> The obvious solution is to use asyn's blocking mode, but there's up
> to 500 ports resulting in as many threads.
Could you please elaborate on why you think this is a problem? It might
not look pretty but in practice CPU overhead might actually be small:
Asyn is using threads because it needs to wait for asynchronous
operations to complete. The pattern is generally: process some data
(which takes a very short time), go to sleep and wait for the next
event/interrupt. Whenever you send a thread to sleep the scheduler is
performing a context switch.

Let's say you have 1000 events/s to process with a single thread. You
wake up 1000 times/s and go to sleep 1000 times/s resulting in 1000
context switches/s. If you are processing the 1000 events with 1000
threads, each of them wakes up once per second and goes to sleep. Again
1000 context switches/s total.

I'm simplify here but CPU overhead might not be as bad as you might
think in the first place. Memory overhead of course is a different story.

-Martin

-- 
Martin Konrad
Facility for Rare Isotope Beams
Michigan State University
640 South Shaw Lane
East Lansing, MI 48824-1321, USA
Tel. 517-908-7253
Email: konrad@frib.msu.edu