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SubjectRe: fair clock use in CFS
On Mon, May 14, 2007 at 10:31:13AM -0400, Daniel Hazelton wrote:
> Hrm... Okay, so you're saying that "fair_clock" runs slower the more process
> there are running to keep the above run-up in "Time Spent on CPU" I noticed
> based solely on your initial example? If that is the case, then I can see the
> fairness - its just not visible from a really quick look at the code and the
> simplified description you gave earlier.

From the code:

update_curr()

delta_fair = delta_exec * NICE_0_LOAD;
do_div(delta_fair, rq->raw_weighted_load);

..

rq->fair_clock += delta_fair;

Although wall clock would have advanced by delta_exec, fair clock
advances only by delta_fair.

More the load on the CPU (rq->raw_weighted_load), slower is this advance
compared to wall clock.



--
Regards,
vatsa
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