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authorDaniel Lezcano <daniel.lezcano@linaro.org>2013-03-02 11:10:11 +0100
committerThomas Gleixner <tglx@linutronix.de>2013-03-07 16:13:26 +0100
commitd2348fb6fdc6d671ad45b62db237f76c8c115603 (patch)
tree30a05c397f91bd8ac32cc904231d9a72ce7b5c1e
parentf9ae39d04ccdec8d8ecf532191b7056c279a22c0 (diff)
downloadblackbird-op-linux-d2348fb6fdc6d671ad45b62db237f76c8c115603.tar.gz
blackbird-op-linux-d2348fb6fdc6d671ad45b62db237f76c8c115603.zip
tick: Dynamically set broadcast irq affinity
When a cpu goes to a deep idle state where its local timer is shutdown, it notifies the time frame work to use the broadcast timer instead. Unfortunately, the broadcast device could wake up any CPU, including an idle one which is not concerned by the wake up at all. So in the worst case an idle CPU will wake up to send an IPI to the CPU whose timer expired. Provide an opt-in feature CLOCK_EVT_FEAT_DYNIRQ which tells the core that is should set the interrupt affinity of the broadcast interrupt to the cpu which has the earliest expiry time. This avoids unnecessary spurious wakeups and IPIs. [ tglx: Adopted to cpumask rework, silenced an uninitialized warning, massaged changelog ] Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: viresh.kumar@linaro.org Cc: jacob.jun.pan@linux.intel.com Cc: linux-arm-kernel@lists.infradead.org Cc: santosh.shilimkar@ti.com Cc: linaro-kernel@lists.linaro.org Cc: patches@linaro.org Cc: rickard.andersson@stericsson.com Cc: vincent.guittot@linaro.org Cc: linus.walleij@stericsson.com Cc: john.stultz@linaro.org Link: http://lkml.kernel.org/r/1362219013-18173-3-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--include/linux/clockchips.h5
-rw-r--r--kernel/time/tick-broadcast.c39
2 files changed, 36 insertions, 8 deletions
diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
index 66346521cb65..494d33ea78f8 100644
--- a/include/linux/clockchips.h
+++ b/include/linux/clockchips.h
@@ -55,6 +55,11 @@ enum clock_event_nofitiers {
#define CLOCK_EVT_FEAT_C3STOP 0x000008
#define CLOCK_EVT_FEAT_DUMMY 0x000010
+/*
+ * Core shall set the interrupt affinity dynamically in broadcast mode
+ */
+#define CLOCK_EVT_FEAT_DYNIRQ 0x000020
+
/**
* struct clock_event_device - clock event device descriptor
* @event_handler: Assigned by the framework to be called by the low
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 70dd98ce18d7..380910db7157 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -401,13 +401,34 @@ struct cpumask *tick_get_broadcast_oneshot_mask(void)
return tick_broadcast_oneshot_mask;
}
-static int tick_broadcast_set_event(struct clock_event_device *bc,
+/*
+ * Set broadcast interrupt affinity
+ */
+static void tick_broadcast_set_affinity(struct clock_event_device *bc,
+ const struct cpumask *cpumask)
+{
+ if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
+ return;
+
+ if (cpumask_equal(bc->cpumask, cpumask))
+ return;
+
+ bc->cpumask = cpumask;
+ irq_set_affinity(bc->irq, bc->cpumask);
+}
+
+static int tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
ktime_t expires, int force)
{
+ int ret;
+
if (bc->mode != CLOCK_EVT_MODE_ONESHOT)
clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
- return clockevents_program_event(bc, expires, force);
+ ret = clockevents_program_event(bc, expires, force);
+ if (!ret)
+ tick_broadcast_set_affinity(bc, cpumask_of(cpu));
+ return ret;
}
int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
@@ -436,7 +457,7 @@ static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
{
struct tick_device *td;
ktime_t now, next_event;
- int cpu;
+ int cpu, next_cpu = 0;
raw_spin_lock(&tick_broadcast_lock);
again:
@@ -447,10 +468,12 @@ again:
/* Find all expired events */
for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
td = &per_cpu(tick_cpu_device, cpu);
- if (td->evtdev->next_event.tv64 <= now.tv64)
+ if (td->evtdev->next_event.tv64 <= now.tv64) {
cpumask_set_cpu(cpu, tmpmask);
- else if (td->evtdev->next_event.tv64 < next_event.tv64)
+ } else if (td->evtdev->next_event.tv64 < next_event.tv64) {
next_event.tv64 = td->evtdev->next_event.tv64;
+ next_cpu = cpu;
+ }
}
/*
@@ -473,7 +496,7 @@ again:
* Rearm the broadcast device. If event expired,
* repeat the above
*/
- if (tick_broadcast_set_event(dev, next_event, 0))
+ if (tick_broadcast_set_event(dev, next_cpu, next_event, 0))
goto again;
}
raw_spin_unlock(&tick_broadcast_lock);
@@ -515,7 +538,7 @@ void tick_broadcast_oneshot_control(unsigned long reason)
if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
if (dev->next_event.tv64 < bc->next_event.tv64)
- tick_broadcast_set_event(bc, dev->next_event, 1);
+ tick_broadcast_set_event(bc, cpu, dev->next_event, 1);
}
} else {
if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
@@ -581,7 +604,7 @@ void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
tick_broadcast_init_next_event(tmpmask,
tick_next_period);
- tick_broadcast_set_event(bc, tick_next_period, 1);
+ tick_broadcast_set_event(bc, cpu, tick_next_period, 1);
} else
bc->next_event.tv64 = KTIME_MAX;
} else {
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