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[Threading] Implement priority boost on wake

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When a thread wakes from a kernel wait, the Xenon scheduler boosts its
effective priority by the increment passed to the signaling call
(KeSetEvent, KeReleaseSemaphore, KeReleaseMutant). The boost is clamped
to the per-thread max_dynamic_priority cap, respects the guest
boost_disabled flag, and is drained on the next quantum expiry.
Guest KTHREAD priority fields are now initialized from parent process
defaults, and the previously unknown fields involved have been renamed
to match their identified purpose.
This commit is contained in:
Herman S.
2026-04-11 17:05:05 +09:00
parent b3d8a21b72
commit 65b74819aa
9 changed files with 127 additions and 47 deletions
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32
src/xenia/kernel/xthread.h
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@@ -298,9 +298,9 @@ struct X_KTHREAD {
uint8_t unk_A5[0xB]; // 0xA5
int32_t apc_disable_count; // 0xB0
xe::be<int32_t> quantum; // 0xB4
uint8_t unk_B8; // 0xB8
uint8_t unk_B9; // 0xB9
uint8_t unk_BA; // 0xBA
uint8_t saturation_increment; // 0xB8
uint8_t base_priority; // 0xB9
uint8_t priority_decrement; // 0xBA
uint8_t boost_disabled; // 0xBB
uint8_t suspend_count; // 0xBC
uint8_t was_preempted; // 0xBD
@@ -310,9 +310,9 @@ struct X_KTHREAD {
// all
TypedGuestPointer<X_KPRCB> a_prcb_ptr; // 0xC0
TypedGuestPointer<X_KPRCB> another_prcb_ptr; // 0xC4
uint8_t unk_C8; // 0xC8
uint8_t unk_C9; // 0xC9
uint8_t unk_CA; // 0xCA
uint8_t process_priority_class; // 0xC8
uint8_t base_priority_copy; // 0xC9
uint8_t max_dynamic_priority; // 0xCA
uint8_t unk_CB; // 0xCB
X_KSPINLOCK timer_list_lock; // 0xCC
xe::be<uint32_t> stack_alloc_base; // 0xD0
@@ -424,14 +424,19 @@ class XThread : public XObject, public cpu::Thread {
// Called periodically (~20ms) by KernelState's timestamp timer to simulate
// the Xenon scheduler's quantum-based priority decay for non-real-time
// threads (priority < 18). Threads that run for longer than one quantum
// (~20ms) have their effective priority decayed toward the base, which
// causes them to drop into lower host priority buckets and prevents
// starvation.
// threads (base_priority < 18). Threads that run for longer than one
// quantum (~20ms) have their effective priority decayed toward the base,
// which causes them to drop into lower host priority buckets and prevents
// starvation. On the first decay step the accumulated priority boost is
// also drained.
void CheckQuantumAndDecay();
// Resets effective priority back to base and restarts the quantum timer.
// Called when a thread wakes from a kernel wait.
void ResetQuantum();
// Called when a thread wakes from a kernel wait. Applies a priority
// boost of |increment| above base_priority (matching the Xenon kernel's
// unwait-boost behavior) and restarts the quantum timer. The boost is
// drained on the next quantum expiry via CheckQuantumAndDecay().
// If increment is 0 or the thread has boost disabled, the priority is
// simply restored to base_priority.
void BoostOnWake(int32_t increment);
// Xbox thread IDs:
// 0 - core 0, thread 0 - user
@@ -504,6 +509,7 @@ class XThread : public XObject, public cpu::Thread {
int32_t priority_ = 0; // current effective priority (may be decayed)
int32_t base_priority_ = 0; // priority floor — decay never goes below this
int32_t boost_amount_ = 0; // accumulated priority boost above base
uint64_t quantum_start_ms_ = 0; // host uptime (ms) when quantum last reset
#if !XE_PLATFORM_WIN32