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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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29
include/linux/sched.h
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@ -1553,6 +1553,35 @@ static inline int set_cpus_allowed(struct task_struct *p, cpumask_t new_mask)
extern unsigned long long sched_clock(void);
#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
static inline void sched_clock_init(void)
{
}
static inline u64 sched_clock_cpu(int cpu)
{
return sched_clock();
}
static inline void sched_clock_tick(void)
{
}
static inline void sched_clock_idle_sleep_event(void)
{
}
static inline void sched_clock_idle_wakeup_event(u64 delta_ns)
{
}
#else
extern void sched_clock_init(void);
extern u64 sched_clock_cpu(int cpu);
extern void sched_clock_tick(void);
extern void sched_clock_idle_sleep_event(void);
extern void sched_clock_idle_wakeup_event(u64 delta_ns);
#endif
/*
* For kernel-internal use: high-speed (but slightly incorrect) per-cpu
* clock constructed from sched_clock():