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sched: add optional support for CONFIG_HAVE_UNSTABLE_SCHED_CLOCK

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this replaces the rq->clock stuff (and possibly cpu_clock()).

 - architectures that have an 'imperfect' hardware clock can set
   CONFIG_HAVE_UNSTABLE_SCHED_CLOCK

 - the 'jiffie' window might be superfulous when we update tick_gtod
   before the __update_sched_clock() call in sched_clock_tick()

 - cpu_clock() might be implemented as:

     sched_clock_cpu(smp_processor_id())

   if the accuracy proves good enough - how far can TSC drift in a
   single jiffie when considering the filtering and idle hooks?

[ mingo@elte.hu: various fixes and cleanups ]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra
2008-05-03 18:29:28 +02:00
committed by Ingo Molnar
parent a5574cf65b
commit 3e51f33fcc
7 changed files with 281 additions and 161 deletions
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2
kernel/sched_fair.c
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@@ -959,7 +959,7 @@ static void yield_task_fair(struct rq *rq)
return;
if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
__update_rq_clock(rq);
update_rq_clock(rq);
/*
* Update run-time statistics of the 'current'.
*/