Re: Overscheduling DOES happen with high web server load.

Ingo Molnar (mingo@chiara.csoma.elte.hu)
Fri, 7 May 1999 18:09:43 +0200 (CEST)


On Fri, 7 May 1999, Rik van Riel wrote:

> It's based on the idea of a priority heap. Processes have
> a quantum and a defer value. The quantum value is the length
> of the process' time slice and the defer value is the time
> at which it will be run next (sort of a deadline).
>
> The process at the top of the heap is the process with the
> lowest (run next) defer value. After a process finishes it's
> time slice, the defer value is incremented (say, by p->priority)
> and the process is sorted down the B-tree. This means that the
> algorithm for selecting the best process is O(1) on UP machines
> and O(log(nr_cpus)) on SMP machines.
>
> Schedule_timeout() can be replaced by a simple resorting of
> the heap. Basically we only need to remove processes from
> the heap if they do blocking I/O or wait for a signal
> (otherwise they would clutter up the heap).

so? And how do you handle VM and CPU (and who knows what type of other
future) affinity?

-- mingo

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