The following commit has been merged into the timers/core branch of tip:
Commit-ID: c94a8537df12708cc03da9120c3c3561ae744ce1
Gitweb: https://git.kernel.org/tip/c94a8537df12708cc03da9120c3c3561ae744ce1
Author: Will Deacon <will@xxxxxxxxxx>
AuthorDate: Mon, 24 May 2021 23:18:16 +01:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Mon, 31 May 2021 17:04:45 +02:00
tick/broadcast: Prefer per-cpu oneshot wakeup timers to broadcast
Some SoCs have two per-cpu timer implementations where the timer with the
higher rating stops in deep idle (i.e. suffers from CLOCK_EVT_FEAT_C3STOP)
but is otherwise preferable to the timer with the lower rating. In such a
design, selecting the higher rated devices relies on a global broadcast
timer and IPIs to wake up from deep idle states.
To avoid the reliance on a global broadcast timer and also to reduce the
overhead associated with the IPI wakeups, extend
tick_install_broadcast_device() to manage per-cpu wakeup timers separately
from the broadcast device.
For now, these timers remain unused.
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210524221818.15850-4-will@xxxxxxxxxx
---
kernel/time/tick-broadcast.c | 59 ++++++++++++++++++++++++++++++++++-
kernel/time/tick-common.c | 2 +-
kernel/time/tick-internal.h | 4 +-
3 files changed, 61 insertions(+), 4 deletions(-)
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index f3f2f4b..0e9e06d 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -33,6 +33,8 @@ static int tick_broadcast_forced;
static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
#ifdef CONFIG_TICK_ONESHOT
+static DEFINE_PER_CPU(struct clock_event_device *, tick_oneshot_wakeup_device);
+
static void tick_broadcast_setup_oneshot(struct clock_event_device *bc);
static void tick_broadcast_clear_oneshot(int cpu);
static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);
@@ -88,13 +90,65 @@ static bool tick_check_broadcast_device(struct clock_event_device *curdev,
return !curdev || newdev->rating > curdev->rating;
}
+#ifdef CONFIG_TICK_ONESHOT
+static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
+{
+ return per_cpu(tick_oneshot_wakeup_device, cpu);
+}
+
+static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
+ int cpu)
+{
+ struct clock_event_device *curdev = tick_get_oneshot_wakeup_device(cpu);
+
+ if (!newdev)
+ goto set_device;
+
+ if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
+ (newdev->features & CLOCK_EVT_FEAT_C3STOP))
+ return false;
+
+ if (!(newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
+ !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
+ return false;
+
+ if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
+ return false;
+
+ if (curdev && newdev->rating <= curdev->rating)
+ return false;
+
+ if (!try_module_get(newdev->owner))
+ return false;
+
+set_device:
+ clockevents_exchange_device(curdev, newdev);
+ per_cpu(tick_oneshot_wakeup_device, cpu) = newdev;
+ return true;
+}
+#else
+static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
+{
+ return NULL;
+}
+
+static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
+ int cpu)
+{
+ return false;
+}
+#endif
+
/*
* Conditionally install/replace broadcast device
*/
-void tick_install_broadcast_device(struct clock_event_device *dev)
+void tick_install_broadcast_device(struct clock_event_device *dev, int cpu)
{
struct clock_event_device *cur = tick_broadcast_device.evtdev;
+ if (tick_set_oneshot_wakeup_device(dev, cpu))
+ return;
+
if (!tick_check_broadcast_device(cur, dev))
return;
@@ -996,6 +1050,9 @@ void hotplug_cpu__broadcast_tick_pull(int deadcpu)
*/
static void tick_broadcast_oneshot_offline(unsigned int cpu)
{
+ if (tick_get_oneshot_wakeup_device(cpu))
+ tick_set_oneshot_wakeup_device(NULL, cpu);
+
/*
* Clear the broadcast masks for the dead cpu, but do not stop
* the broadcast device!
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index e15bc0e..d663249 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -373,7 +373,7 @@ out_bc:
/*
* Can the new device be used as a broadcast device ?
*/
- tick_install_broadcast_device(newdev);
+ tick_install_broadcast_device(newdev, cpu);
}
/**
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 7a981c9..30c8963 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -61,7 +61,7 @@ extern ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt);
/* Broadcasting support */
# ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
extern int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu);
-extern void tick_install_broadcast_device(struct clock_event_device *dev);
+extern void tick_install_broadcast_device(struct clock_event_device *dev, int cpu);
extern int tick_is_broadcast_device(struct clock_event_device *dev);
extern void tick_suspend_broadcast(void);
extern void tick_resume_broadcast(void);
@@ -72,7 +72,7 @@ extern int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq);
extern struct tick_device *tick_get_broadcast_device(void);
extern struct cpumask *tick_get_broadcast_mask(void);
# else /* !CONFIG_GENERIC_CLOCKEVENTS_BROADCAST: */
-static inline void tick_install_broadcast_device(struct clock_event_device *dev) { }
+static inline void tick_install_broadcast_device(struct clock_event_device *dev, int cpu) { }
static inline int tick_is_broadcast_device(struct clock_event_device *dev) { return 0; }
static inline int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu) { return 0; }
static inline void tick_do_periodic_broadcast(struct clock_event_device *d) { }
|