mirror of
https://github.com/20kdc/OC-KittenOS.git
synced 2024-11-23 10:58:06 +11:00
77 lines
2.0 KiB
Plaintext
77 lines
2.0 KiB
Plaintext
This is an overview of what a program
|
|
can expect from the scheduler.
|
|
|
|
The kernel's scheduling is entirely,
|
|
and I mean entirely, timer-based.
|
|
|
|
Everything in the kernel,
|
|
that has to occur the next time the
|
|
CPU has reached the main loop,
|
|
is, without exception, a timer,
|
|
apart from the timer system itself.
|
|
|
|
That last note is important, since as
|
|
the timer system controls sleeping,
|
|
it must use computer.pullSignal -
|
|
thus, that part of the mechanism is
|
|
not in itself a timer - it is the
|
|
mechanism that waits for timers.
|
|
|
|
Signals that have been retrieved with
|
|
computer.pullSignal, however, do
|
|
become timers.
|
|
|
|
Timers are kept in a list, and have
|
|
their "target uptime" - the
|
|
computer.uptime() at which they are
|
|
due to be executed, their callback,
|
|
and after the callback, a list of
|
|
arguments to give to the callback.
|
|
|
|
The current time as KittenOS NEO
|
|
sees it is available as os.uptime().
|
|
(and the address, as os.address() -
|
|
bit of a cheat, but who's counting?)
|
|
|
|
This source is always in seconds, and
|
|
so KittenOS NEO timing is always in
|
|
seconds.
|
|
|
|
The scheduling loop's precise details
|
|
are in the kernel itself, and any
|
|
precise description would be a
|
|
translation into pseudocode of what
|
|
is already there.
|
|
|
|
But it suffices to note that the
|
|
scheduling loop works by, 16 times
|
|
at most, executing and removing all
|
|
timers from first defined to last
|
|
that have passed their time,
|
|
and getting the minimum time of all
|
|
unexecuted timers during each loop.
|
|
|
|
The last minimum time, if it exists,
|
|
is then bounded to at least 0.05,
|
|
an OC minimum value for a yield.
|
|
|
|
The pullSignal is then called with
|
|
the bounded time, if any.
|
|
|
|
(If no bounded time exists, then the
|
|
system goes into more or less a deep
|
|
freeze, which is useful to conserve
|
|
energy, even when apps are "running"
|
|
but aren't using timers.)
|
|
|
|
If there is any signal, distEvent is
|
|
called to distribute it to those
|
|
processes with the right accessses,
|
|
with an "h." prefix.
|
|
|
|
-- This is released into
|
|
the public domain.
|
|
-- No warranty is provided,
|
|
implied or otherwise.
|
|
|