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