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SubjectRe: Scheduler fixes

On Thu, 25 Jun 1998, Chris Wedgwood wrote:

> I guess CONFIG_EXACT_PROCTIMES would make everyone happy (having this
> dependent upon the processor selection and perhaps APM).

no, we want to keep the number of kernel config variations as low as
possible. There are different conflicting issues here, but mass-ifdefs in
the core kernel code is not nice, especially as the ifdef separates two
completely different concepts. So the debugging work will be hard. This is
not a driver ifdef, it's not a separate kernel feature. This ifdef
separates two _competing_ pieces of code. We really dont want to do that,
unless justified by other factors.

note that we can do the 'timestamp' trick with non-cycle-counter CPUs too,
we just use 'jiffies' instead of cycles. If you think about it, it will
give the current system usage metrics ... this way the difference between
'old' and 'new' CPUs is much visible, and only in include files. Think of
them as CPUs with a 100 Hz cycle counter :)

of course it's more expensive than doing the sampling in the interrupt
handler, and the overhead is not '100 times a second', but 'once per
reschedule'.

-- mingo


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