sched: add optional support for CONFIG_HAVE_UNSTABLE_SCHED_CLOCK

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

View file

@ -602,6 +602,7 @@ asmlinkage void __init start_kernel(void)
softirq_init();
timekeeping_init();
time_init();
sched_clock_init();
profile_init();
if (!irqs_disabled())
printk("start_kernel(): bug: interrupts were enabled early\n");