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SubjectRe: Scheduler fixes
Hi,

> btw, we could do _exact_ process accounting if we want to, at the price of
> ~10-15 cycles per schedule(). we can just read the cycle counter (industry
> standard on most leading CPUs ;), add the delta to the process and do the
> math later, whenever someone (top) tries to access the values. This way we
> could even differentiate between IRQ cycles, kernel cycles, kernel thread
> cycles, idle cycles and user-space cycles. Is this an important and
> fundamental enough feature to justify those 10-15 cycles?

IMHO it would be very useful to smart scheduling algorithms, but this is
certainly a post-2.2 issue.

Anyway, for 2.1 I propose the following two simple changes:

o Introduce a switch count to each process. This should make all the
time eaters visible which was the point of Pavel's patch. Precise
accounting of time spent probably requires per-switch TSC reads.

o Add current time to /proc/<pid>/stat, making corrections
of time shifts between stat reads of different processes without
zillions of calls to gettimeofday() possible.

Have a nice fortnight
--
Martin `MJ' Mares <mj@ucw.cz> http://atrey.karlin.mff.cuni.cz/~mj/
Faculty of Math and Physics, Charles University, Prague, Czech Rep., Earth
"System going down at 1:45 for disk crashing."

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