Re: Ichbiah 2022 compiler mode

[Niklas Holsti <niklas.holsti@tidorum.invalid>]

On 2024-09-12 12:04, J-P. Rosen wrote:

   [...]

> Well, tasks are not only for speeding up code. They can be a very useful 
> design tool (active objects, independant activities). I think the Ada 
> model is clean and simple, I would hate to see it disappear.

I agree.

>> I'm less certain about the value of priorities, [...]

> Priorities are just optimization on how to manage cores when there are 
> not enough of them.

In some contexts it could be optimization -- for example, to increase 
throughput in a soft real-time system -- but in hard real-time systems 
priorities (or deadlines) are needed for correctness, not just for 
optimizatiion.

> I know that people use priorities to guarantee mutual exclusion, and 
> other properties. All these algorithms were designed at the time of 
> mono-CPU machines, but they fail on multi-cores.

In SW for multi-core systems it can be beneficial to collect tasks that 
frequently interact with each other or with the same single-user 
resources in the same core, and then the mono-core mutual-exclusion 
algorithms like priority ceiling inheritance can be used for that group 
of tasks, while using other algorithms for mutual exclusion between 
tasks running in different cores.