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sched: Remove needless round trip nsecs <-> tick conversion of steal time 

When update_rq_clock_task() accounts the pending steal time for a task,
it converts the steal delta from nsecs to tick then from tick to nsecs.

There is no apparent good reason for doing that though because both
the task clock and the prev steal delta are u64 and store values
in nsecs.

So lets remove the needless conversion.

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This commit is contained in:
Frederic Weisbecker 2014-03-05 17:05:57 +01:00
parent dee08a72de
commit 300a9d887e
2 changed files with 0 additions and 16 deletions
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6
kernel/sched/core.c
View File

@ -823,19 +823,13 @@ static void update_rq_clock_task(struct rq *rq, s64 delta)
#endif
#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
if (static_key_false((&paravirt_steal_rq_enabled))) {
u64 st;
steal = paravirt_steal_clock(cpu_of(rq));
steal -= rq->prev_steal_time_rq;
if (unlikely(steal > delta))
steal = delta;
st = steal_ticks(steal);
steal = st * TICK_NSEC;
rq->prev_steal_time_rq += steal;
delta -= steal;
}
#endif

10
kernel/sched/sched.h
View File

@ -1214,16 +1214,6 @@ extern void update_idle_cpu_load(struct rq *this_rq);
extern void init_task_runnable_average(struct task_struct *p);
#ifdef CONFIG_PARAVIRT
static inline u64 steal_ticks(u64 steal)
{
if (unlikely(steal > NSEC_PER_SEC))
return div_u64(steal, TICK_NSEC);
return __iter_div_u64_rem(steal, TICK_NSEC, &steal);
}
#endif
static inline void inc_nr_running(struct rq *rq)
{
rq->nr_running++;