Re: non-preemptive tasking on GNAT 2020 Windows 10 multicore AMD

[Dennis Lee Bieber <wlfraed@ix.netcom.com>]

On Sat, 12 Jun 2021 15:21:35 -0700 (PDT), Dan Winslow
<dandwinslow@gmail.com> declaimed the following:


>Kind of disheartening, and I'm not sure where to go next. I don't so much require a non-preemptive scheduler, but my inability to affect any behavior at all for teh tasking is really wierd, and seems like a bug of the underlying system. Anyone have any ideas? Is there some fundamental flaw in my little test program I'm missing?

	I suspect part of the problem may be that the GNAT runtime defers to
the OS for how tasks (threads/processes) are implemented (AdaCore probably
gets a fortune for configuring a bare-bones runtime that supports tasking).
Since Windows will have a lot of time-slicing and interrupts, ANY
task/thread is subject to preemption -- and on preemption, it likely goes
to the end of any round-robin within priorities queue.

https://www.microsoftpressstore.com/articles/article.aspx?p=2233328&seqNum=7

{Interesting -- about half-way down that page it states that a preempted
thread is put on the /head/ of the queue for its priority level, so that it
can later be restarted to "finish" its time quantum}


-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
	wlfraed@ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/