Re: O(1) scheduler
Davide Libenzi (dlibenzi@maticad.it)
Mon, 31 May 1999 09:09:33 +0200
>>The run-priority of processes is determined by fine-grain time
>>accounting. The scheduler would read the RTSC register (or the timer
>>chip internal counter on pre-Pentium processors) once each time it needs
>>rescheduling, and decrease the time budget of the currently active by
>>the amount of time the process has been run. If the integer part (run
>>priority) decreases, the process has to be moved to another bucket, and
>>there is inserted at the front. Now the scheduler would schedule the
>>first process in the highest bucket.
>
>This has some problems:
>
>- old CPUs that don't have a TSC, so you need a fall back.
>- the standard TSC counts interrupts and bottom halves too. It would
>be unfair to charge them to a process (I believe the SMP scheduler in 2.2
>has the same problem)
I think the idea is good, even if We don't have a TSC ( We can count timer
tics for example ).
The _really_ important deal is avoid linear scan of process list.
All this, is of course, IMVHO.
Cheers,
Davide.
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