Subject:
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RE: LegOS scheduler questions
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Newsgroups:
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lugnet.robotics.rcx.legos
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Date:
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Tue, 24 Apr 2001 03:48:19 GMT
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Viewed:
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3903 times
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On 24 Apr 2001 03:17:00 +0000, Subir Biswas wrote:
> Folks,
>
> This is my first day with Leogs. I just installed Legos,
> compiled a program and have run it successfully. Haven't
> got a chance to take a look at the kernel source.
> I have the following questions and any response will
> be greatly appreciated.
>
> 1. Is the time-slicing always on? I assume it is. If yes,
> can one turn it off without actually changing the kernel
> source.
I don't /think/ so, but I don't have time to check to be certain and it
has been now literally 10 months since I looked at kernel source. :\
> 2. What is the time-slice size? (10ms, 100ms ....)
See #1. :\
> 3. How many threads Legos can support?
By design? As many as you can throw at it- there is no hard-coded limit,
and the data structures used are relatively flexible. Practically
speaking, probably somewhere in the region of 10-16 (maybe less) before
you start running into memory problems.
> 4. Can more than one thread have same priority with
> stable behavior?
Yes. That was not always the case but the kernel now handles that
cleanly.
> 5. Are wait_event(), RELEASED(), PRESSED() all these
> functions do busy-waiting? i.e. do they continuously
> monitor the relevant inputs without yielding the
> CPU to the scheduler. Or there is an interrupt type
> mechanism that wakes a thread up which is waiting on
> a wait_event() call.
For all intents and purposes, they are waiting in a tight loop with a
yield. So, the calls aren't blocking- other threads can do things while
one thread is doing a wait_event(). That said, if you are waiting for a
/very/ transient event (a very tiny light spike, for example) since you
are looping and not waiting for a true interrupt it is possible to miss
events.
Luis
> Thanks,
>
> - Subir
>
> PS: please send a copy of the reply to my personal mail
> address as well.
>
>
> NetZero Platinum
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--
Luis Villa
Duke University '01
http://tieguy.org/
"Liberace outlived Elvis, thereby suggesting to many there is no God, or if
there is one, He lacks taste."
-www.lileks.com
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Message is in Reply To:
 | | RE: LegOS scheduler questions
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| Folks, This is my first day with Leogs. I just installed Legos, compiled a program and have run it successfully. Haven't got a chance to take a look at the kernel source. I have the following questions and any response will be greatly appreciated. (...) (25 years ago, 24-Apr-01, to lugnet.robotics.rcx.legos)
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