From 37edcce1fa3f87cf982dd166cb441787d9ec0e2d Mon Sep 17 00:00:00 2001
From: Cacodemon345 <wahil1976@outlook.com>
Date: Sat, 4 Oct 2025 02:03:11 +0600
Subject: [PATCH] Call timeBeginPeriod only once on startup (#6273)

Use SetProcessInformation to make the OS better handle our threads on big/small cores
---
 src/qt/qt_main.cpp     |  9 +++++
 src/qt/qt_platform.cpp | 78 ++++++++++++++++++++++++++++++++++++------
 src/qt/qt_ui.cpp       |  4 ---
 3 files changed, 77 insertions(+), 14 deletions(-)

diff --git a/src/qt/qt_main.cpp b/src/qt/qt_main.cpp
index 8fbcfe7d3..5f9101d47 100644
--- a/src/qt/qt_main.cpp
+++ b/src/qt/qt_main.cpp
@@ -98,6 +98,7 @@ extern "C" {
 #include <86box/timer.h>
 #include <86box/nvr.h>
 extern int qt_nvr_save(void);
+extern void exit_pause(void);
 
 bool cpu_thread_running = false;
 }
@@ -753,6 +754,14 @@ main(int argc, char *argv[])
     discord_load();
 #endif
 
+#ifdef Q_OS_WINDOWS
+    // On Win32 the accuracy of Sleep() depends on the timer resolution, which can be set by calling timeBeginPeriod
+    // https://learn.microsoft.com/en-us/windows/win32/api/timeapi/nf-timeapi-timebeginperiod
+    exit_pause();
+    timeBeginPeriod(1);
+    atexit([] () -> void { timeEndPeriod(1); });
+#endif
+
     main_window = new MainWindow();
     if (startMaximized) {
         main_window->showMaximized();
diff --git a/src/qt/qt_platform.cpp b/src/qt/qt_platform.cpp
index ad49e5e7c..6b60adffa 100644
--- a/src/qt/qt_platform.cpp
+++ b/src/qt/qt_platform.cpp
@@ -453,6 +453,65 @@ plat_munmap(void *ptr, size_t size)
 }
 
 extern bool cpu_thread_running;
+
+#ifdef Q_OS_WINDOWS
+/* SetThreadDescription was added in 14393 and SetProcessInformation in 8. Revisit if we ever start requiring 10. */
+static void *kernel32_handle = NULL;
+static HRESULT(WINAPI *pSetThreadDescription)(HANDLE hThread, PCWSTR lpThreadDescription) = NULL;
+static HRESULT(WINAPI *pSetProcessInformation)(HANDLE hProcess, PROCESS_INFORMATION_CLASS ProcessInformationClass, LPVOID ProcessInformation, DWORD ProcessInformationSize) = NULL;
+static dllimp_t kernel32_imports[] = {
+  // clang-format off
+    { "SetThreadDescription",  &pSetThreadDescription  },
+    { "SetProcessInformation", &pSetProcessInformation },
+    { NULL,                    NULL                    }
+  // clang-format on
+};
+
+static void
+enter_pause(void)
+{
+    PROCESS_POWER_THROTTLING_STATE state{};
+    state.Version = PROCESS_POWER_THROTTLING_CURRENT_VERSION;
+    state.ControlMask = PROCESS_POWER_THROTTLING_EXECUTION_SPEED | PROCESS_POWER_THROTTLING_IGNORE_TIMER_RESOLUTION;
+    state.StateMask = PROCESS_POWER_THROTTLING_EXECUTION_SPEED | PROCESS_POWER_THROTTLING_IGNORE_TIMER_RESOLUTION;
+
+    if (!kernel32_handle) {
+        kernel32_handle = dynld_module("kernel32.dll", kernel32_imports);
+        if (!kernel32_handle) {
+            kernel32_handle = kernel32_imports; /* store dummy pointer to avoid trying again */
+            pSetThreadDescription = NULL;
+            pSetProcessInformation = NULL;
+        }
+    }
+
+    if (pSetProcessInformation) {
+        pSetProcessInformation(GetCurrentProcess(), ProcessPowerThrottling, (LPVOID)&state, sizeof(state));
+    }
+}
+
+void
+exit_pause(void)
+{
+    PROCESS_POWER_THROTTLING_STATE state{};
+    state.Version = PROCESS_POWER_THROTTLING_CURRENT_VERSION;
+    state.ControlMask = PROCESS_POWER_THROTTLING_EXECUTION_SPEED | PROCESS_POWER_THROTTLING_IGNORE_TIMER_RESOLUTION;
+    state.StateMask = 0;
+
+    if (!kernel32_handle) {
+        kernel32_handle = dynld_module("kernel32.dll", kernel32_imports);
+        if (!kernel32_handle) {
+            kernel32_handle = kernel32_imports; /* store dummy pointer to avoid trying again */
+            pSetThreadDescription = NULL;
+            pSetProcessInformation = NULL;
+        }
+    }
+
+    if (pSetProcessInformation) {
+        pSetProcessInformation(GetCurrentProcess(), ProcessPowerThrottling, (LPVOID)&state, sizeof(state));
+    }
+}
+#endif
+
 void
 plat_pause(int p)
 {
@@ -477,6 +536,14 @@ plat_pause(int p)
     if ((p == 0) && (time_sync & TIME_SYNC_ENABLED))
         nvr_time_sync();
 
+#ifdef Q_OS_WINDOWS
+    if (p) {
+        enter_pause();
+    } else {
+        exit_pause();
+    }
+#endif
+
     do_pause(p);
     if (p) {
         if (mouse_capture)
@@ -842,21 +909,12 @@ void
 plat_set_thread_name(void *thread, const char *name)
 {
 #ifdef Q_OS_WINDOWS
-    /* SetThreadDescription was added in 14393. Revisit if we ever start requiring 10. */
-    static void *kernel32_handle = NULL;
-    static HRESULT(WINAPI *pSetThreadDescription)(HANDLE hThread, PCWSTR lpThreadDescription) = NULL;
-    static dllimp_t kernel32_imports[] = {
-      // clang-format off
-        { "SetThreadDescription", &pSetThreadDescription },
-        { NULL,                   NULL                   }
-      // clang-format on
-    };
-
     if (!kernel32_handle) {
         kernel32_handle = dynld_module("kernel32.dll", kernel32_imports);
         if (!kernel32_handle) {
             kernel32_handle = kernel32_imports; /* store dummy pointer to avoid trying again */
             pSetThreadDescription = NULL;
+            pSetProcessInformation = NULL;
         }
     }
 
diff --git a/src/qt/qt_ui.cpp b/src/qt/qt_ui.cpp
index d4a257887..e93ed9786 100644
--- a/src/qt/qt_ui.cpp
+++ b/src/qt/qt_ui.cpp
@@ -65,11 +65,7 @@ void
 plat_delay_ms(uint32_t count)
 {
 #ifdef Q_OS_WINDOWS
-    // On Win32 the accuracy of Sleep() depends on the timer resolution, which can be set by calling timeBeginPeriod
-    // https://learn.microsoft.com/en-us/windows/win32/api/timeapi/nf-timeapi-timebeginperiod
-    timeBeginPeriod(1);
     Sleep(count);
-    timeEndPeriod(1);
 #else
     QThread::msleep(count);
 #endif