On Wed, Jun 26, 2013 at 10:46:33AM -0600, David Ahern wrote:
> On 6/26/13 1:05 AM, Peter Zijlstra wrote:
> >>What is the expectation that the feature provides? not a whole lot of
> >>documentation on it. I walked down the path wondering if it solved an odd
> >>problem we are seeing with the CFS in 2.6.27 kernel.
> >
> >Its supposed to use hrtimers for slice expiry instead of the regular tick.
>
> So theoretically CPU bound tasks would get preempted sooner? That was my
> guess/hope anyways.
Doth the below worketh?
---
kernel/sched/core.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9b1f2e5..0d8eb45 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -370,13 +370,6 @@ static struct rq *this_rq_lock(void)
#ifdef CONFIG_SCHED_HRTICK
/*
* Use HR-timers to deliver accurate preemption points.
- *
- * Its all a bit involved since we cannot program an hrt while holding the
- * rq->lock. So what we do is store a state in in rq->hrtick_* and ask for a
- * reschedule event.
- *
- * When we get rescheduled we reprogram the hrtick_timer outside of the
- * rq->lock.
*/
static void hrtick_clear(struct rq *rq)
@@ -404,6 +397,15 @@ static enum hrtimer_restart hrtick(struct hrtimer *timer)
}
#ifdef CONFIG_SMP
+
+static int __hrtick_restart(struct rq *rq)
+{
+ struct hrtimer *timer = &rq->hrtick_timer;
+ ktime_t time = hrtimer_get_softexpires(timer);
+
+ return __hrtimer_start_range_ns(timer, time, 0,
HRTIMER_MODE_ABS_PINNED, 0);
+}
+
/*
* called from hardirq (IPI) context
*/
@@ -412,7 +414,7 @@ static void __hrtick_start(void *arg)
struct rq *rq = arg;
raw_spin_lock(&rq->lock);
- hrtimer_restart(&rq->hrtick_timer);
+ __hrtick_restart(rq);
rq->hrtick_csd_pending = 0;
raw_spin_unlock(&rq->lock);
}
@@ -430,7 +432,7 @@ void hrtick_start(struct rq *rq, u64 delay)
hrtimer_set_expires(timer, time);
if (rq == this_rq()) {
- hrtimer_restart(timer);
+ __hrtick_restart(rq);
} else if (!rq->hrtick_csd_pending) {
__smp_call_function_single(cpu_of(rq), &rq->hrtick_csd, 0);
rq->hrtick_csd_pending = 1;
--
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