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sched: new task placement for vruntime

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add proper new task placement for the vruntime based math too.

( note: introduces a swap() macro, but the swap token is too
  widely used in the kernel namespace for a generic version
  to be added without changing non-scheduler code - so this
  cleanup will be done separately. )

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Peter Zijlstra 2007-10-15 17:00:04 +02:00 committed by Ingo Molnar
parent 6cb5819514
commit 4d78e7b656
1 changed files with 27 additions and 9 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

36
kernel/sched_fair.c
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@ -203,6 +203,20 @@ static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
* Scheduling class statistics methods:
*/
static u64 __sched_period(unsigned long nr_running)
{
u64 period = sysctl_sched_latency;
unsigned long nr_latency =
sysctl_sched_latency / sysctl_sched_min_granularity;
if (unlikely(nr_running > nr_latency)) {
period *= nr_running;
do_div(period, nr_latency);
}
return period;
}
/*
* Calculate the preemption granularity needed to schedule every
* runnable task once per sysctl_sched_latency amount of time.
@ -1103,6 +1117,8 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr)
}
}
#define swap(a,b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0)
/*
* Share the fairness runtime between parent and child, thus the
* total amount of pressure for CPU stays equal - new tasks
@ -1118,14 +1134,9 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
sched_info_queued(p);
update_curr(cfs_rq);
se->vruntime = cfs_rq->min_vruntime;
update_stats_enqueue(cfs_rq, se);
/*
* Child runs first: we let it run before the parent
* until it reschedules once. We set up the key so that
* it will preempt the parent:
*/
se->fair_key = curr->fair_key -
niced_granularity(curr, sched_granularity(cfs_rq)) - 1;
/*
* The first wait is dominated by the child-runs-first logic,
* so do not credit it with that waiting time yet:
@ -1138,9 +1149,16 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
* -granularity/2, so initialize the task with that:
*/
if (sched_feat(START_DEBIT))
se->wait_runtime = -(sched_granularity(cfs_rq) / 2);
se->wait_runtime = -(__sched_period(cfs_rq->nr_running+1) / 2);
if (sysctl_sched_child_runs_first &&
curr->vruntime < se->vruntime) {
dequeue_entity(cfs_rq, curr, 0);
swap(curr->vruntime, se->vruntime);
enqueue_entity(cfs_rq, curr, 0);
}
se->vruntime = cfs_rq->min_vruntime;
update_stats_enqueue(cfs_rq, se);
__enqueue_entity(cfs_rq, se);
resched_task(rq->curr);