From ede552ab25e23e2aa64b6953c4ef848699266881 Mon Sep 17 00:00:00 2001
From: Pawel Dziepak <pdziepak@quarnos.org>
Date: Mon, 23 Dec 2013 22:06:33 +0100
Subject: [PATCH] scheduler: Keep thread effective priority cached

---
 .../kernel/scheduler/scheduler_thread.cpp     | 18 ++++++++++++++
 .../kernel/scheduler/scheduler_thread.h       | 24 +++++++++----------
 2 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/src/system/kernel/scheduler/scheduler_thread.cpp b/src/system/kernel/scheduler/scheduler_thread.cpp
index 3bcb4d79be..ab45e78de0 100644
--- a/src/system/kernel/scheduler/scheduler_thread.cpp
+++ b/src/system/kernel/scheduler/scheduler_thread.cpp
@@ -22,6 +22,7 @@ ThreadData::Init()
 {
 	fPriorityPenalty = 0;
 	fAdditionalPenalty = 0;
+	fEffectivePriority = -1;
 
 	fTimeLeft = 0;
 	fStolenTime = 0;
@@ -121,6 +122,23 @@ ThreadData::ComputeQuantum()
 }
 
 
+void
+ThreadData::_ComputeEffectivePriority() const
+{
+	if (thread_is_idle_thread(fThread))
+		fEffectivePriority = B_IDLE_PRIORITY;
+	else if (fThread->priority >= B_FIRST_REAL_TIME_PRIORITY)
+		fEffectivePriority = fThread->priority;
+	else {
+		fEffectivePriority = fThread->priority;
+		fEffectivePriority -= _GetPenalty();
+
+		ASSERT(fEffectivePriority < B_FIRST_REAL_TIME_PRIORITY);
+		ASSERT(fEffectivePriority >= B_LOWEST_ACTIVE_PRIORITY);
+	}
+}
+
+
 inline CoreEntry*
 ThreadData::_ChooseCore() const
 {
diff --git a/src/system/kernel/scheduler/scheduler_thread.h b/src/system/kernel/scheduler/scheduler_thread.h
index 7a8b6163cf..4260e82586 100644
--- a/src/system/kernel/scheduler/scheduler_thread.h
+++ b/src/system/kernel/scheduler/scheduler_thread.h
@@ -74,6 +74,8 @@ private:
 	inline	int32		_GetPenalty() const;
 	inline	int32		_GetMinimalPriority() const;
 
+			void		_ComputeEffectivePriority() const;
+
 	inline	CoreEntry*	_ChooseCore() const;
 	inline	CPUEntry*	_ChooseCPU(CoreEntry* core,
 							bool& rescheduleNeeded) const;
@@ -98,6 +100,8 @@ private:
 			int32		fPriorityPenalty;
 			int32		fAdditionalPenalty;
 
+	mutable	int32		fEffectivePriority;
+
 			bigtime_t	fTimeLeft;
 
 			bigtime_t	fMeasureActiveTime;
@@ -133,18 +137,9 @@ ThreadData::ShouldRebalance() const
 inline int32
 ThreadData::GetEffectivePriority() const
 {
-	if (thread_is_idle_thread(fThread))
-		return B_IDLE_PRIORITY;
-	if (fThread->priority >= B_FIRST_REAL_TIME_PRIORITY)
-		return fThread->priority;
-
-	int32 effectivePriority = fThread->priority;
-	effectivePriority -= _GetPenalty();
-
-	ASSERT(effectivePriority < B_FIRST_REAL_TIME_PRIORITY);
-	ASSERT(effectivePriority >= B_LOWEST_ACTIVE_PRIORITY);
-
-	return effectivePriority;
+	if (fEffectivePriority == -1)
+		_ComputeEffectivePriority();
+	return fEffectivePriority;
 }
 
 
@@ -158,6 +153,7 @@ ThreadData::IncreasePenalty()
 
 	TRACE("increasing thread %ld penalty\n", fThread->id);
 
+	fEffectivePriority = -1;
 	int32 oldPenalty = fPriorityPenalty++;
 
 	ASSERT(fThread->priority - oldPenalty >= B_LOWEST_ACTIVE_PRIORITY);
@@ -173,8 +169,10 @@ ThreadData::IncreasePenalty()
 inline void
 ThreadData::CancelPenalty()
 {
-	if (fPriorityPenalty != 0)
+	if (fPriorityPenalty != 0) {
 		TRACE("cancelling thread %ld penalty\n", fThread->id);
+		fEffectivePriority = -1;
+	}
 
 	fAdditionalPenalty = 0;
 	fPriorityPenalty = 0;