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sched: fix ideal_runtime calculations for reniced tasks 

fix ideal_runtime:

  - do not scale it using niced_granularity()
    it is against sum_exec_delta, so its wall-time, not fair-time.

  - move the whole check into __check_preempt_curr_fair()
    so that wakeup preemption can also benefit from the new logic.

this also results in code size reduction:

   text    data     bss     dec     hex filename
  13391     228    1204   14823    39e7 sched.o.before
  13369     228    1204   14801    39d1 sched.o.after

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 2007-09-05 14:32:49 +02:00 committed by Ingo Molnar
parent 4a55b45036
commit 1169783085
1 changed files with 22 additions and 16 deletions
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38
kernel/sched_fair.c
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@ -678,11 +678,31 @@ __check_preempt_curr_fair(struct cfs_rq *cfs_rq, struct sched_entity *se,
struct sched_entity *curr, unsigned long granularity)
{
s64 __delta = curr->fair_key - se->fair_key;
unsigned long ideal_runtime, delta_exec;
/*
* ideal_runtime is compared against sum_exec_runtime, which is
* walltime, hence do not scale.
*/
ideal_runtime = max(sysctl_sched_latency / cfs_rq->nr_running,
(unsigned long)sysctl_sched_min_granularity);
/*
* If we executed more than what the latency constraint suggests,
* reduce the rescheduling granularity. This way the total latency
* of how much a task is not scheduled converges to
* sysctl_sched_latency:
*/
delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
if (delta_exec > ideal_runtime)
granularity = 0;
/*
* Take scheduling granularity into account - do not
* preempt the current task unless the best task has
* a larger than sched_granularity fairness advantage:
*
* scale granularity as key space is in fair_clock.
*/
if (__delta > niced_granularity(curr, granularity))
resched_task(rq_of(cfs_rq)->curr);
@ -731,7 +751,6 @@ static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
unsigned long gran, ideal_runtime, delta_exec;
struct sched_entity *next;
/*
@ -748,21 +767,8 @@ static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
if (next == curr)
return;
gran = sched_granularity(cfs_rq);
ideal_runtime = niced_granularity(curr,
max(sysctl_sched_latency / cfs_rq->nr_running,
(unsigned long)sysctl_sched_min_granularity));
/*
* If we executed more than what the latency constraint suggests,
* reduce the rescheduling granularity. This way the total latency
* of how much a task is not scheduled converges to
* sysctl_sched_latency:
*/
delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
if (delta_exec > ideal_runtime)
gran = 0;
__check_preempt_curr_fair(cfs_rq, next, curr, gran);
__check_preempt_curr_fair(cfs_rq, next, curr,
sched_granularity(cfs_rq));
}
/**************************************************