3 further range-hrtimer patches

3 further range-hrtimer patches

[Arjan van de Ven]

Hi,

as reply to this email I have 3 further patches for the range-hrtimer
patchkit:

Patch 1 and 2 change the futex and nanosleep code to also use
range-hrtimers with the per process slack

Patch 3 adds a "peek-a-timer" capability; this is used from the cpuidle
loop to run any soft-expired timers just before looking at how long
we'll be idle (for determining the C-state etc); that way we'll have a
longer idle period.

I'll add these patches to the git tree in a day or two, adjusted for
comments based on this posting


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org

[PATCH 1/3] hrtimer: make the futex() system call use the per process slack value

[Arjan van de Ven]

From: Arjan van de Ven <arjan@linux.intel.com>
Subject: [PATCH] hrtimer: make the futex() system call use the per process slack value

This patch makes the futex() system call use the per process
slack value; with this users are able to externally control existing
applications to reduce the wakeup rate.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
 kernel/futex.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 4cd5b43..8af1002 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1296,10 +1296,14 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
 		if (!abs_time)
 			schedule();
 		else {
+			unsigned long slack;
+			slack = current->timer_slack_ns;
+			if (rt_task(current))
+				slack = 0;
 			hrtimer_init_on_stack(&t.timer, CLOCK_MONOTONIC,
 						HRTIMER_MODE_ABS);
 			hrtimer_init_sleeper(&t, current);
-			hrtimer_set_expires(&t.timer, *abs_time);
+			hrtimer_set_expires_range_ns(&t.timer, *abs_time, slack);
 
 			hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS);
 			if (!hrtimer_active(&t.timer))
-- 
1.5.5.1



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org

[PATCH 2/3] hrtimer: make the nanosleep() syscall use the per process slack

[Arjan van de Ven]

From: Arjan van de Ven <arjan@linux.intel.com>
Subject: [PATCH] hrtimer: make the nanosleep() syscall use the per process slack

This patch makes the nanosleep() system call use the per process
slack value; with this users are able to externally control existing
applications to reduce the wakeup rate.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
 kernel/hrtimer.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index a022209..9a4c901 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1563,9 +1563,14 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
 	struct restart_block *restart;
 	struct hrtimer_sleeper t;
 	int ret = 0;
+	unsigned long slack;
+
+	slack = current->timer_slack_ns;
+	if (rt_task(current))
+		slack = 0;
 
 	hrtimer_init_on_stack(&t.timer, clockid, mode);
-	hrtimer_set_expires(&t.timer, timespec_to_ktime(*rqtp));
+	hrtimer_set_expires_range_ns(&t.timer, timespec_to_ktime(*rqtp), slack);
 	if (do_nanosleep(&t, mode))
 		goto out;
 
-- 
1.5.5.1



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org

[PATCH 3/3] hrtimer: peek at the timer queue just before going idle

[Arjan van de Ven]

From: Arjan van de Ven <arjan@linux.intel.com>
Subject: [PATCH] hrtimer: peek at the timer queue just before going idle

As part of going idle, we already look at the time of the next timer event to determine
which C-state to select etc.

This patch adds functionality that causes the timers that are past their
soft expire time, to fire at this time, before we calculate the next wakeup
time. This functionality will thus avoid wakeups by running timers before
going idle rather than specially waking up for it.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
 drivers/cpuidle/cpuidle.c |    7 +++++++
 include/linux/hrtimer.h   |    5 +++++
 kernel/hrtimer.c          |   30 ++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 0 deletions(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 5ce07b5..2e31484 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -16,6 +16,7 @@
 #include <linux/cpu.h>
 #include <linux/cpuidle.h>
 #include <linux/ktime.h>
+#include <linux/hrtimer.h>
 
 #include "cpuidle.h"
 
@@ -60,6 +61,12 @@ static void cpuidle_idle_call(void)
 		return;
 	}
 
+	/*
+	 * run any timers that can be run now, at this point
+	 * before calculating the idle duration etc.
+	 */
+	hrtimer_peek_ahead_timers();
+
 	/* ask the governor for the next state */
 	next_state = cpuidle_curr_governor->select(dev);
 	if (need_resched())
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 301c2c8..1ca3978 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -326,6 +326,11 @@ static inline int hrtimer_is_hres_active(struct hrtimer *timer)
 extern ktime_t ktime_get(void);
 extern ktime_t ktime_get_real(void);
 
+
+DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
+extern void hrtimer_peek_ahead_timers(void);
+
+
 /* Exported timer functions: */
 
 /* Initialize timers: */
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index b1dacd3..d152c46 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1381,6 +1381,36 @@ void hrtimer_interrupt(struct clock_event_device *dev)
 		raise_softirq(HRTIMER_SOFTIRQ);
 }
 
+/**
+ * hrtimer_peek_ahead_timers -- run soft-expired timers now
+ *
+ * hrtimer_peek_ahead_timers will peek at the timer queue of
+ * the current cpu and check if there are any timers for which
+ * the soft expires time has passed. If any such timers exist,
+ * they are run immediately and then removed from the timer queue.
+ *
+ */
+void hrtimer_peek_ahead_timers(void)
+{
+	unsigned long flags;
+	struct tick_device *td;
+	struct clock_event_device *dev;
+
+	if (hrtimer_hres_active())
+		return;
+
+	local_irq_save(flags);
+	td = &__get_cpu_var(tick_cpu_device);
+	if (!td)
+		goto out;
+	dev = td->evtdev;
+	if (!dev)
+		goto out;
+	hrtimer_interrupt(dev);
+out:
+	local_irq_restore(flags);	
+}
+
 static void run_hrtimer_softirq(struct softirq_action *h)
 {
 	run_hrtimer_pending(&__get_cpu_var(hrtimer_bases));
-- 
1.5.5.1


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org