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Comment and reorganize the scheduler

This commit is contained in:
Fernando Sahmkow 2019-04-02 08:03:44 -04:00 committed by FernandoS27
parent b5d1e44782
commit 3a94e7ea33
2 changed files with 107 additions and 101 deletions
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170
src/core/hle/kernel/scheduler.cpp
View File

@ -19,6 +19,11 @@
namespace Kernel {
/*
* SelectThreads, Yield functions originally by TuxSH.
* licensed under GPLv2 or later under exception provided by the author.
*/
void GlobalScheduler::AddThread(SharedPtr<Thread> thread) {
thread_list.push_back(std::move(thread));
}
@ -29,15 +34,23 @@ void GlobalScheduler::RemoveThread(Thread* thread) {
}
/*
* SelectThreads, Yield functions originally by TuxSH.
* licensed under GPLv2 or later under exception provided by the author.
* UnloadThread selects a core and forces it to unload its current thread's context
*/
void GlobalScheduler::UnloadThread(s32 core) {
Scheduler& sched = Core::System::GetInstance().Scheduler(core);
sched.UnloadThread();
}
/*
* SelectThread takes care of selecting the new scheduled thread.
* It does it in 3 steps:
* - First a thread is selected from the top of the priority queue. If no thread
* is obtained then we move to step two, else we are done.
* - Second we try to get a suggested thread that's not assigned to any core or
* that is not the top thread in that core.
* - Third is no suggested thread is found, we do a second pass and pick a running
* thread in another core and swap it with its current thread.
*/
void GlobalScheduler::SelectThread(u32 core) {
auto update_thread = [](Thread* thread, Scheduler& sched) {
if (thread != sched.selected_thread) {
@ -51,105 +64,58 @@ void GlobalScheduler::SelectThread(u32 core) {
};
Scheduler& sched = Core::System::GetInstance().Scheduler(core);
Thread* current_thread = nullptr;
// Step 1: Get top thread in schedule queue.
current_thread = scheduled_queue[core].empty() ? nullptr : scheduled_queue[core].front();
if (!current_thread) {
Thread* winner = nullptr;
std::set<s32> sug_cores;
for (auto thread : suggested_queue[core]) {
s32 this_core = thread->GetProcessorID();
Thread* thread_on_core = nullptr;
if (this_core >= 0) {
thread_on_core = scheduled_queue[this_core].front();
}
if (this_core < 0 || thread != thread_on_core) {
winner = thread;
break;
}
sug_cores.insert(this_core);
if (current_thread) {
update_thread(current_thread, sched);
return;
}
// Step 2: Try selecting a suggested thread.
Thread* winner = nullptr;
std::set<s32> sug_cores;
for (auto thread : suggested_queue[core]) {
s32 this_core = thread->GetProcessorID();
Thread* thread_on_core = nullptr;
if (this_core >= 0) {
thread_on_core = scheduled_queue[this_core].front();
}
if (winner && winner->GetPriority() > 2) {
if (winner->IsRunning()) {
UnloadThread(winner->GetProcessorID());
}
TransferToCore(winner->GetPriority(), core, winner);
current_thread = winner;
} else {
for (auto& src_core : sug_cores) {
auto it = scheduled_queue[src_core].begin();
it++;
if (it != scheduled_queue[src_core].end()) {
Thread* thread_on_core = scheduled_queue[src_core].front();
Thread* to_change = *it;
if (thread_on_core->IsRunning() || to_change->IsRunning()) {
UnloadThread(src_core);
}
TransferToCore(thread_on_core->GetPriority(), core, thread_on_core);
current_thread = thread_on_core;
}
if (this_core < 0 || thread != thread_on_core) {
winner = thread;
break;
}
sug_cores.insert(this_core);
}
// if we got a suggested thread, select it, else do a second pass.
if (winner && winner->GetPriority() > 2) {
if (winner->IsRunning()) {
UnloadThread(winner->GetProcessorID());
}
TransferToCore(winner->GetPriority(), core, winner);
update_thread(winner, sched);
return;
}
// Step 3: Select a suggested thread from another core
for (auto& src_core : sug_cores) {
auto it = scheduled_queue[src_core].begin();
it++;
if (it != scheduled_queue[src_core].end()) {
Thread* thread_on_core = scheduled_queue[src_core].front();
Thread* to_change = *it;
if (thread_on_core->IsRunning() || to_change->IsRunning()) {
UnloadThread(src_core);
}
TransferToCore(thread_on_core->GetPriority(), core, thread_on_core);
current_thread = thread_on_core;
break;
}
}
update_thread(current_thread, sched);
}
void GlobalScheduler::SelectThreads() {
auto update_thread = [](Thread* thread, Scheduler& sched) {
if (thread != sched.selected_thread) {
if (thread == nullptr) {
++sched.idle_selection_count;
}
sched.selected_thread = thread;
}
sched.context_switch_pending = sched.selected_thread != sched.current_thread;
std::atomic_thread_fence(std::memory_order_seq_cst);
};
auto& system = Core::System::GetInstance();
std::unordered_set<Thread*> picked_threads;
// This maintain the "current thread is on front of queue" invariant
std::array<Thread*, NUM_CPU_CORES> current_threads;
for (u32 i = 0; i < NUM_CPU_CORES; i++) {
Scheduler& sched = system.Scheduler(i);
current_threads[i] = scheduled_queue[i].empty() ? nullptr : scheduled_queue[i].front();
if (current_threads[i])
picked_threads.insert(current_threads[i]);
update_thread(current_threads[i], sched);
}
// Do some load-balancing. Allow second pass.
std::array<Thread*, NUM_CPU_CORES> current_threads_2 = current_threads;
for (u32 i = 0; i < NUM_CPU_CORES; i++) {
if (!scheduled_queue[i].empty()) {
continue;
}
Thread* winner = nullptr;
for (auto thread : suggested_queue[i]) {
if (thread->GetProcessorID() < 0 || thread != current_threads[i]) {
if (picked_threads.count(thread) == 0 && !thread->IsRunning()) {
winner = thread;
break;
}
}
}
if (winner) {
TransferToCore(winner->GetPriority(), i, winner);
current_threads_2[i] = winner;
picked_threads.insert(winner);
}
}
// See which to-be-current threads have changed & update accordingly
for (u32 i = 0; i < NUM_CPU_CORES; i++) {
Scheduler& sched = system.Scheduler(i);
if (current_threads_2[i] != current_threads[i]) {
update_thread(current_threads_2[i], sched);
}
}
reselection_pending.store(false, std::memory_order_release);
}
/*
* YieldThread takes a thread and moves it to the back of the it's priority list
* This operation can be redundant and no scheduling is changed if marked as so.
*/
void GlobalScheduler::YieldThread(Thread* yielding_thread) {
// Note: caller should use critical section, etc.
u32 core_id = static_cast<u32>(yielding_thread->GetProcessorID());
@ -164,6 +130,12 @@ void GlobalScheduler::YieldThread(Thread* yielding_thread) {
AskForReselectionOrMarkRedundant(yielding_thread, winner);
}
/*
* YieldThreadAndBalanceLoad takes a thread and moves it to the back of the it's priority list.
* Afterwards, tries to pick a suggested thread from the suggested queue that has worse time or
* a better priority than the next thread in the core.
* This operation can be redundant and no scheduling is changed if marked as so.
*/
void GlobalScheduler::YieldThreadAndBalanceLoad(Thread* yielding_thread) {
// Note: caller should check if !thread.IsSchedulerOperationRedundant and use critical section,
// etc.
@ -213,6 +185,12 @@ void GlobalScheduler::YieldThreadAndBalanceLoad(Thread* yielding_thread) {
AskForReselectionOrMarkRedundant(yielding_thread, winner);
}
/*
* YieldThreadAndWaitForLoadBalancing takes a thread and moves it out of the scheduling queue
* and into the suggested queue. If no thread can be squeduled afterwards in that core,
* a suggested thread is obtained instead.
* This operation can be redundant and no scheduling is changed if marked as so.
*/
void GlobalScheduler::YieldThreadAndWaitForLoadBalancing(Thread* yielding_thread) {
// Note: caller should check if !thread.IsSchedulerOperationRedundant and use critical section,
// etc.
@ -256,8 +234,8 @@ void GlobalScheduler::YieldThreadAndWaitForLoadBalancing(Thread* yielding_thread
void GlobalScheduler::AskForReselectionOrMarkRedundant(Thread* current_thread, Thread* winner) {
if (current_thread == winner) {
// Nintendo (not us) has a nullderef bug on current_thread->owner, but which is never
// triggered.
// TODO(blinkhawk): manage redundant operations, this is not implemented.
// as its mostly an optimization.
// current_thread->SetRedundantSchedulerOperation();
} else {
reselection_pending.store(true, std::memory_order_release);

38
src/core/hle/kernel/scheduler.h
View File

@ -48,14 +48,12 @@ public:
}
void Schedule(u32 priority, u32 core, Thread* thread) {
ASSERT_MSG(thread->GetProcessorID() == core,
"Thread must be assigned to this core.");
ASSERT_MSG(thread->GetProcessorID() == core, "Thread must be assigned to this core.");
scheduled_queue[core].add(thread, priority);
}
void SchedulePrepend(u32 priority, u32 core, Thread* thread) {
ASSERT_MSG(thread->GetProcessorID() == core,
"Thread must be assigned to this core.");
ASSERT_MSG(thread->GetProcessorID() == core, "Thread must be assigned to this core.");
scheduled_queue[core].add(thread, priority, false);
}
@ -84,17 +82,47 @@ public:
Suggest(priority, source_core, thread);
}
/*
* UnloadThread selects a core and forces it to unload its current thread's context
*/
void UnloadThread(s32 core);
void SelectThreads();
/*
* SelectThread takes care of selecting the new scheduled thread.
* It does it in 3 steps:
* - First a thread is selected from the top of the priority queue. If no thread
* is obtained then we move to step two, else we are done.
* - Second we try to get a suggested thread that's not assigned to any core or
* that is not the top thread in that core.
* - Third is no suggested thread is found, we do a second pass and pick a running
* thread in another core and swap it with its current thread.
*/
void SelectThread(u32 core);
bool HaveReadyThreads(u32 core_id) {
return !scheduled_queue[core_id].empty();
}
/*
* YieldThread takes a thread and moves it to the back of the it's priority list
* This operation can be redundant and no scheduling is changed if marked as so.
*/
void YieldThread(Thread* thread);
/*
* YieldThreadAndBalanceLoad takes a thread and moves it to the back of the it's priority list.
* Afterwards, tries to pick a suggested thread from the suggested queue that has worse time or
* a better priority than the next thread in the core.
* This operation can be redundant and no scheduling is changed if marked as so.
*/
void YieldThreadAndBalanceLoad(Thread* thread);
/*
* YieldThreadAndWaitForLoadBalancing takes a thread and moves it out of the scheduling queue
* and into the suggested queue. If no thread can be squeduled afterwards in that core,
* a suggested thread is obtained instead.
* This operation can be redundant and no scheduling is changed if marked as so.
*/
void YieldThreadAndWaitForLoadBalancing(Thread* thread);
u32 CpuCoresCount() const {