OpenEuphoria

Re: Multitasking: active waiting!?

• Posted by Robert Craig <rds at RapidEuphoria.com> Apr 18, 2006
• 467 views

Ryan W. Johnson wrote:
> Rob: I tried the new multitasking routines, and i realized that the CPU is at
> 100% even though the tasks are not running all the time. Here is how i set up
> the scheduling:
> 
> }}}
<eucode>
>    task_schedule(task_kernMain_HighPri, {0.005, 0.01})
>    task_schedule(task_kernMain_LowPri, {0.5, 1})
>    task_schedule(task_kernMain_100ms, {0.1, 0.1})
>    task_schedule(task_kernMain_500ms, {0.5, 0.5})
>    task_schedule(task_kernMain_1s, {1, 1})
>    task_schedule(task_kernMain_2s, {2, 2})
>    task_schedule(task_kernMain_10s, {10, 10})
>    task_schedule(task_kernMain_60s, {60, 60})
> }}}
<eucode>
> 
> Even if i change the first line to {0.5, 1} it still maxes the CPU. Shouldn't
> euphoria allow the program to sleep between tasks, even if only for 0.01
> seconds? I just cannot use this if it's gonna how the CPU!

The way it works at the moment, the Euphoria task scheduler 
calls sleep() only when there is a gap of at least 1 second
until the next task is due to resume. That's because sleep() only
has a resolution of 1 second (that's the worst case 
across all platforms). For smaller gaps it just spins its 
wheels in a loop. 

It might be wasteful to sleep for a tiny fraction of a second, 
giving up control, and hoping the O/S will give it back in time. 
Also, other than DOS, the O/S should be able to grab control 
pre-emptively whenever it wants to run another process, 
regardless of whether you are sleeping or not.
 
> This brings up another point that i meant to bring up a long time ago:
> could you change sleep() so that it could have a higher resolution, such as
> 0.01 seconds?

Yes, I would like to have a higher-resolution sleep(), and I will
look into it. I don't think all the various C compiler libraries
provide that directly though.

Thanks,
   Rob Craig
   Rapid Deployment Software
   http://www.RapidEuphoria.com