File linux-2.6.33-default-slack.patch of Package kernel-n900-2.6.33.3-11.2.armv7l

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File linux-2.6.33-default-slack.patch of Package kernel-n900-2.6.33.3-11.2.armv7l (Revision 02bf593a4dc3bfa2906427f1c2fb476a)

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From: Arjan van de Ven <arjan@linux.intel.com>
Subject: Increase the default timer slack for better power efficiency
Patch-mainline: Never

Meego tweak to a default value:
1 msec default slack for select() and co is good enough for non-realtime systems
such as desktops, and we get some power savings because of that.
It also allows us to simplify the automatic estimator to be more predicatable.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
 fs/select.c               |   33 +--------------------------------
 include/linux/init_task.h |    2 +-
 2 files changed, 2 insertions(+), 33 deletions(-)

--- a/fs/select.c
+++ b/fs/select.c
@@ -44,34 +44,8 @@
 
 #define MAX_SLACK	(100 * NSEC_PER_MSEC)
 
-static long __estimate_accuracy(struct timespec *tv)
-{
-	long slack;
-	int divfactor = 1000;
-
-	if (tv->tv_sec < 0)
-		return 0;
-
-	if (task_nice(current) > 0)
-		divfactor = divfactor / 5;
-
-	if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor))
-		return MAX_SLACK;
-
-	slack = tv->tv_nsec / divfactor;
-	slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);
-
-	if (slack > MAX_SLACK)
-		return MAX_SLACK;
-
-	return slack;
-}
-
 static long estimate_accuracy(struct timespec *tv)
 {
-	unsigned long ret;
-	struct timespec now;
-
 	/*
 	 * Realtime tasks get a slack of 0 for obvious reasons.
 	 */
@@ -79,12 +53,7 @@ static long estimate_accuracy(struct tim
 	if (rt_task(current))
 		return 0;
 
-	ktime_get_ts(&now);
-	now = timespec_sub(*tv, now);
-	ret = __estimate_accuracy(&now);
-	if (ret < current->timer_slack_ns)
-		return current->timer_slack_ns;
-	return ret;
+	return current->timer_slack_ns;
 }
 
 
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -166,7 +166,7 @@ extern struct cred init_cred;
 	.cpu_timers	= INIT_CPU_TIMERS(tsk.cpu_timers),		\
 	.fs_excl	= ATOMIC_INIT(0),				\
 	.pi_lock	= __RAW_SPIN_LOCK_UNLOCKED(tsk.pi_lock),	\
-	.timer_slack_ns = 50000, /* 50 usec default slack */		\
+	.timer_slack_ns = 1000000, /* 1 msec default slack */		\
 	.pids = {							\
 		[PIDTYPE_PID]  = INIT_PID_LINK(PIDTYPE_PID),		\
 		[PIDTYPE_PGID] = INIT_PID_LINK(PIDTYPE_PGID),		\

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File linux-2.6.33-default-slack.patch of Package kernel-n900-2.6.33.3-11.2.armv7l (Revision 02bf593a4dc3bfa2906427f1c2fb476a)

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