From e4ea637227d7cf9a53bc89317990b8a22a76780a Mon Sep 17 00:00:00 2001
From: Pawel Dziepak <pdziepak@quarnos.org>
Date: Fri, 3 Jan 2014 19:34:25 +0100
Subject: [PATCH] scheduler: Disable load tracking when not needed

---
 src/system/kernel/scheduler/scheduler.cpp      | 13 +++++++++++--
 src/system/kernel/scheduler/scheduler_common.h |  2 ++
 src/system/kernel/scheduler/scheduler_cpu.cpp  |  6 ++++--
 .../kernel/scheduler/scheduler_thread.cpp      | 18 ++++++++++++++++++
 src/system/kernel/scheduler/scheduler_thread.h | 17 +----------------
 5 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/src/system/kernel/scheduler/scheduler.cpp b/src/system/kernel/scheduler/scheduler.cpp
index 41546f05da..bb3caa8034 100644
--- a/src/system/kernel/scheduler/scheduler.cpp
+++ b/src/system/kernel/scheduler/scheduler.cpp
@@ -136,6 +136,8 @@ scheduler_mode gCurrentModeID;
 scheduler_mode_operations* gCurrentMode;
 
 bool gSingleCore;
+bool gCPUFrequencyManagement;
+bool gTrackLoad;
 
 CPUEntry* gCPUEntries;
 
@@ -533,7 +535,6 @@ reschedule(int32 nextState)
 
 	Thread* nextThread = nextThreadData->GetThread();
 	ASSERT(!gCPU[thisCPU].disabled || thread_is_idle_thread(nextThread));
-
 	// update CPU heap
 	CoreCPUHeapLocker cpuLocker(core);
 	cpu->UpdatePriority(nextThreadData->GetEffectivePriority());
@@ -803,8 +804,16 @@ init()
 	if (result != B_OK)
 		return result;
 
-	gCoreCount = coreCount;
+	// disable parts of the scheduler logic that are not needed
 	gSingleCore = coreCount == 1;
+	gCPUFrequencyManagement = increase_cpu_performance(0) == B_OK;
+	gTrackLoad = !gSingleCore || gCPUFrequencyManagement;
+	dprintf("scheduler switches: single core: %s, cpufreq: %s, load tracking:"
+		" %s\n", gSingleCore ? "true" : "false",
+		gCPUFrequencyManagement ? "true" : "false",
+		gTrackLoad ? "true" : "false");
+
+	gCoreCount = coreCount;
 	gPackageCount = packageCount;
 
 	gCPUEntries = new(std::nothrow) CPUEntry[cpuCount];
diff --git a/src/system/kernel/scheduler/scheduler_common.h b/src/system/kernel/scheduler/scheduler_common.h
index 02c96917f2..812fb7d8d0 100644
--- a/src/system/kernel/scheduler/scheduler_common.h
+++ b/src/system/kernel/scheduler/scheduler_common.h
@@ -43,6 +43,8 @@ const int kVeryHighLoad = (kMaxLoad + kHighLoad) / 2;
 const int kLoadDifference = kMaxLoad * 20 / 100;
 
 extern bool gSingleCore;
+extern bool gCPUFrequencyManagement;
+extern bool gTrackLoad;
 
 
 void init_debug_commands();
diff --git a/src/system/kernel/scheduler/scheduler_cpu.cpp b/src/system/kernel/scheduler/scheduler_cpu.cpp
index 08987fd49a..a88c041693 100644
--- a/src/system/kernel/scheduler/scheduler_cpu.cpp
+++ b/src/system/kernel/scheduler/scheduler_cpu.cpp
@@ -164,7 +164,6 @@ CPUEntry::ComputeLoad()
 {
 	SCHEDULER_ENTER_FUNCTION();
 
-	ASSERT(!gSingleCore);
 	ASSERT(fCPUNumber == smp_get_current_cpu());
 
 	int oldLoad = compute_load(fMeasureTime, fMeasureActiveTime, fLoad);
@@ -247,7 +246,7 @@ CPUEntry::TrackActivity(ThreadData* oldThreadData, ThreadData* nextThreadData)
 
 	oldThreadData->ComputeLoad();
 	nextThreadData->ComputeLoad();
-	if (!gSingleCore && !cpuEntry->disabled)
+	if (gTrackLoad && !cpuEntry->disabled)
 		ComputeLoad();
 
 	Thread* nextThread = nextThreadData->GetThread();
@@ -267,6 +266,9 @@ CPUEntry::_RequestPerformanceLevel(ThreadData* threadData)
 {
 	SCHEDULER_ENTER_FUNCTION();
 
+	if (!gCPUFrequencyManagement)
+		return;
+
 	if (gCPU[fCPUNumber].disabled) {
 		decrease_cpu_performance(kCPUPerformanceScaleMax);
 		return;
diff --git a/src/system/kernel/scheduler/scheduler_thread.cpp b/src/system/kernel/scheduler/scheduler_thread.cpp
index 4d5ea1909b..ec84ee46ec 100644
--- a/src/system/kernel/scheduler/scheduler_thread.cpp
+++ b/src/system/kernel/scheduler/scheduler_thread.cpp
@@ -115,6 +115,24 @@ ThreadData::ChooseCoreAndCPU(CoreEntry*& targetCore, CPUEntry*& targetCPU)
 }
 
 
+void
+ThreadData::ComputeLoad()
+{
+	SCHEDULER_ENTER_FUNCTION();
+
+	if (!gTrackLoad)
+		return;
+
+	if (fLastInterruptTime > 0) {
+		bigtime_t interruptTime = gCPU[smp_get_current_cpu()].interrupt_time;
+		interruptTime -= fLastInterruptTime;
+		fMeasureActiveTime -= interruptTime;
+	}
+
+	compute_load(fMeasureTime, fMeasureActiveTime, fLoad);
+}
+
+
 bigtime_t
 ThreadData::ComputeQuantum()
 {
diff --git a/src/system/kernel/scheduler/scheduler_thread.h b/src/system/kernel/scheduler/scheduler_thread.h
index 98cc660cc6..debcf2d98b 100644
--- a/src/system/kernel/scheduler/scheduler_thread.h
+++ b/src/system/kernel/scheduler/scheduler_thread.h
@@ -56,7 +56,7 @@ public:
 	inline	bool		Dequeue();
 
 	inline	void		UpdateActivity(bigtime_t active);
-	inline	void		ComputeLoad();
+			void		ComputeLoad();
 
 	inline	bool		HasQuantumEnded(bool wasPreempted, bool hasYielded);
 			bigtime_t	ComputeQuantum();
@@ -318,21 +318,6 @@ ThreadData::UpdateActivity(bigtime_t active)
 }
 
 
-inline void
-ThreadData::ComputeLoad()
-{
-	SCHEDULER_ENTER_FUNCTION();
-
-	if (fLastInterruptTime > 0) {
-		bigtime_t interruptTime = gCPU[smp_get_current_cpu()].interrupt_time;
-		interruptTime -= fLastInterruptTime;
-		fMeasureActiveTime -= interruptTime;
-	}
-
-	compute_load(fMeasureTime, fMeasureActiveTime, fLoad);
-}
-
-
 inline bool
 ThreadData::HasQuantumEnded(bool wasPreempted, bool hasYielded)
 {