summaryrefslogtreecommitdiff
path: root/kernel/sched_fair.c
diff options
context:
space:
mode:
authorPeter Zijlstra <a.p.zijlstra@chello.nl>2007-10-15 17:00:04 +0200
committerIngo Molnar <mingo@elte.hu>2007-10-15 17:00:04 +0200
commit4d78e7b656aa6440c337302fe065338ce840a64e (patch)
tree3013b8b4971ba9b6e3e250d36404c89d7a7c107f /kernel/sched_fair.c
parent6cb58195143b55d4c427d92f8425bec2b0d9c56c (diff)
downloadlwn-4d78e7b656aa6440c337302fe065338ce840a64e.tar.gz
lwn-4d78e7b656aa6440c337302fe065338ce840a64e.zip
sched: new task placement for vruntime
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>
Diffstat (limited to 'kernel/sched_fair.c')
-rw-r--r--kernel/sched_fair.c36
1 files changed, 27 insertions, 9 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 7041dc697855..95487e3c8b06 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -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);