Re: [RFC][PATCH][2.6.6] Replacing CPU scheduler active and expired with a single array
From: Ingo Molnar (mingo_at_elte.hu)
Date: 05/28/04
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Date: Fri, 28 May 2004 11:05:36 +0200 To: Peter Williams <peterw@aurema.com>
* 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
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