scheduler: Introduce strong and weak priority penalties

src/system/kernel/scheduler/low_latency.cpp

@@ -164,7 +164,7 @@ scheduler_mode_operations gSchedulerLowLatencyMode = {
 	100,
 	{ 2, 25 },
 
-	50000,
+	10000,
 
 	switch_to_mode,
 	set_cpu_enabled,

src/system/kernel/scheduler/scheduler_thread.cpp

@@ -217,14 +217,14 @@ ThreadData::ComputeQuantum()
 	quantum += fStolenTime;
 	fStolenTime = 0;
 
-	int32 threadCount = (fCore->ThreadCount() + 1) / fCore->CPUCount();
+	int32 threadCount = fCore->ThreadCount() / fCore->CPUCount();
-	threadCount = max_c(threadCount, 1);
+	if (threadCount >= 1) {
-
+		quantum
-	quantum = std::min(gCurrentMode->maximum_latency / threadCount, quantum);
+			= std::min(gCurrentMode->maximum_latency / threadCount, quantum);
-	quantum = std::max(quantum,	gCurrentMode->minimal_quantum);
+		quantum = std::max(quantum,	gCurrentMode->minimal_quantum);
+	}
 
 	fTimeLeft = quantum;
-
 	return quantum;
 }
 

src/system/kernel/scheduler/scheduler_thread.h

@@ -44,11 +44,11 @@ public:
 
 	inline	int32		GetEffectivePriority() const;
 
+	inline	bool		IsCPUBound() const;
+
 	inline	void		CancelPenalty();
 	inline	bool		ShouldCancelPenalty() const;
 
-	inline	bool		IsCPUBound() const	{ return fAdditionalPenalty != 0; }
-
 			bool		ChooseCoreAndCPU(CoreEntry*& targetCore,
 							CPUEntry*& targetCPU);
 
@@ -85,7 +85,7 @@ public:
 	static	void		ComputeQuantumLengths();
 
 private:
-	inline	void		_IncreasePenalty();
+	inline	void		_IncreasePenalty(bool strong);
 	inline	int32		_GetPenalty() const;
 
 			void		_ComputeEffectivePriority() const;
@@ -175,7 +175,7 @@ ThreadData::GetEffectivePriority() const
 
 
 inline void
-ThreadData::_IncreasePenalty()
+ThreadData::_IncreasePenalty(bool strong)
 {
 	SCHEDULER_ENTER_FUNCTION();
 
@@ -187,12 +187,14 @@ ThreadData::_IncreasePenalty()
 	TRACE("increasing thread %ld penalty\n", fThread->id);
 
 	fReceivedPenalty = true;
-	int32 oldPenalty = fPriorityPenalty++;
+	int32 oldPenalty = fPriorityPenalty;
+	if (strong)
+		fPriorityPenalty++;
 
 	ASSERT(fThread->priority - oldPenalty >= B_LOWEST_ACTIVE_PRIORITY);
 
 	const int kMinimalPriority = _GetMinimalPriority();
-	if (fThread->priority - oldPenalty <= kMinimalPriority) {
+	if (!strong || fThread->priority - oldPenalty <= kMinimalPriority) {
 		fPriorityPenalty = oldPenalty;
 		fAdditionalPenalty++;
 	}
@@ -201,6 +203,14 @@ ThreadData::_IncreasePenalty()
 }
 
 
+inline bool
+ThreadData::IsCPUBound() const
+{
+	SCHEDULER_ENTER_FUNCTION();
+	return fAdditionalPenalty != 0 && fPriorityPenalty != 0;
+}
+
+
 inline void
 ThreadData::CancelPenalty()
 {
@@ -255,7 +265,7 @@ ThreadData::GoesAway()
 	SCHEDULER_ENTER_FUNCTION();
 
 	if (!fReceivedPenalty)
-		_IncreasePenalty();
+		_IncreasePenalty(false);
 	fHasSlept = true;
 
 	fLastInterruptTime = 0;
@@ -400,7 +410,7 @@ ThreadData::HasQuantumEnded(bool wasPreempted, bool hasYielded)
 
 	if (fTimeLeft == 0) {
 		if (!fReceivedPenalty && !fHasSlept)
-			_IncreasePenalty();
+			_IncreasePenalty(true);
 		fReceivedPenalty = false;
 		fHasSlept = false;
 	}