Re: [RFC][PATCH][2.6.6] Replacing CPU scheduler active and expired with a single array

[Ingo Molnar <mingo@elte.hu>]

* Peter Williams <peterw@aurema.com> wrote:

> -- at the end of each time slice (or when waking up) each task is
> given a complete new time slice and, if class SCHED_NORMAL, is put in
> a priority slot given by (static_prio + MAX_BONUS - interactive_bonus)

this is the Achilles' heel of approaches that try to get rid of the
active/expired array and/or try to get rid of timeslice tracking. A
CPU-bound task which schedules away for small amounts of time will get a
disproportionatly larger share of the CPU than a CPU-bound task that
doesnt schedule at all.

just try it - run a task that runs 95% of the time and sleeps 5% of the
time, and run a (same prio) task that runs 100% of the time. With the
current scheduler the slightly-sleeping task gets 45% of the CPU, the
looping one gets 55% of the CPU. With your patch the slightly-sleeping
process can easily monopolize 90% of the CPU!

	Ingo