On Sat, 2007-10-13 at 11:17 +0200, Peter Zijlstra wrote:
> > Ah, but HRTICK is not compatible with PREEMPT_RESTRICT, it will be
> > similar to !WAKEUP_PREEMPT.
>
> (I do plan to fix that eventually, just need to do it)
I guess something like this ought to do, but its a tad late so I'm quite
sure :-)
---
kernel/sched_fair.c | 44 +++++++++++++++++++++++++++++++++++++-------
1 file changed, 37 insertions(+), 7 deletions(-)
Index: linux-2.6/kernel/sched_fair.c
===================================================================
--- linux-2.6.orig/kernel/sched_fair.c
+++ linux-2.6/kernel/sched_fair.c
@@ -737,6 +737,24 @@ static inline struct sched_entity *paren
#endif /* CONFIG_FAIR_GROUP_SCHED */
+/*
+ * does pse (newly woken task) preempt se (current task)
+ */
+static int wakeup_preempt(struct sched_entity *se, struct sched_entity *pse)
+{
+ s64 delta, gran;
+
+ delta = se->vruntime - pse->vruntime;
+ gran = sysctl_sched_wakeup_granularity;
+ if (unlikely(se->load.weight != NICE_0_LOAD))
+ gran = calc_delta_fair(gran, &se->load);
+
+ if (delta > gran)
+ return 1;
+
+ return 0;
+}
+
#ifdef CONFIG_SCHED_HRTICK
static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
@@ -764,6 +782,24 @@ static void hrtick_start_fair(struct rq
if (!requeue)
delta = max(10000LL, delta);
+ /*
+ * if we delayed wakeup preemption, shorten the slice to at most
+ * 1 jiffy (does this call for yet another sysctl_sched_?)
+ */
+ if (sched_feat(PREEMPT_RESTRICT) && first_fair(cfs_rq)) {
+ struct sched_entity *next = __pick_next_entity(cfs_rq);
+
+ if (wakeup_preempt(se, next)) {
+ u64 wakeup = NSEC_PER_SEC / HZ;
+ s64 delta2 = wakeup - ran;
+
+ if (delta2 < 0)
+ resched_task(rq->curr);
+ else
+ delta = min(delta, delta2);
+ }
+ }
+
hrtick_start(rq, delta, requeue);
}
}
@@ -866,7 +902,6 @@ static void check_preempt_wakeup(struct
struct task_struct *curr = rq->curr;
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
struct sched_entity *se = &curr->se, *pse = &p->se;
- s64 delta, gran;
if (unlikely(rt_prio(p->prio))) {
update_rq_clock(rq);
@@ -887,12 +922,7 @@ static void check_preempt_wakeup(struct
pse = parent_entity(pse);
}
- delta = se->vruntime - pse->vruntime;
- gran = sysctl_sched_wakeup_granularity;
- if (unlikely(se->load.weight != NICE_0_LOAD))
- gran = calc_delta_fair(gran, &se->load);
-
- if (delta > gran) {
+ if (wakeup_preempt(se, pse)) {
int now = !sched_feat(PREEMPT_RESTRICT);
if (now || p->prio < curr->prio || !se->peer_preempt++)
-
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