[MISC] Allow user to override process priority class

src/xenia/base/system.h

@@ -27,6 +27,8 @@ void ShutdownAndroidSystem();
 void LaunchWebBrowser(const std::string_view url);
 void LaunchFileExplorer(const std::filesystem::path& path);
 
+bool SetProcessPriorityClass(const uint32_t priority_class);
+
 enum class SimpleMessageBoxType {
   Help,
   Warning,

src/xenia/base/system_android.cc

@@ -294,4 +294,6 @@ void ShowSimpleMessageBox(SimpleMessageBoxType type, std::string_view message) {
   // Java VM for the calling thread is needed.
 }
 
+bool SetProcessPriorityClass(const uint32_t priority_class) { return true; }
+
 }  // namespace xe

src/xenia/base/system_gnulinux.cc

@@ -67,4 +67,6 @@ void ShowSimpleMessageBox(SimpleMessageBoxType type, std::string_view message) {
   }
 }
 
+bool SetProcessPriorityClass(const uint32_t priority_class) { return true; }
+
 }  // namespace xe

src/xenia/base/system_win.cc

@@ -7,6 +7,7 @@
  ******************************************************************************
  */
 
+#include <map>
 #include "xenia/base/platform_win.h"
 #include "xenia/base/string.h"
 #include "xenia/base/system.h"
@@ -48,4 +49,19 @@ void ShowSimpleMessageBox(SimpleMessageBoxType type,
               type_flags);
 }
 
+static std::map<const uint32_t, DWORD> xeniaToWindowsPriorityClassMapping = {
+    {0, NORMAL_PRIORITY_CLASS},
+    {1, ABOVE_NORMAL_PRIORITY_CLASS},
+    {2, HIGH_PRIORITY_CLASS},
+    {3, REALTIME_PRIORITY_CLASS}};
+
+bool SetProcessPriorityClass(const uint32_t priority_class) {
+  if (!xeniaToWindowsPriorityClassMapping.count(priority_class)) {
+    return false;
+  }
+
+  return SetPriorityClass(GetCurrentProcess(),
+                          xeniaToWindowsPriorityClassMapping[priority_class]);
+}
+
 }  // namespace xe

src/xenia/emulator.cc

@@ -86,6 +86,12 @@ DECLARE_int32(user_language);
 
 DECLARE_bool(allow_plugins);
 
+DEFINE_int32(priority_class, 0,
+             "Forces Xenia to use different process priority than default one. "
+             "It might affect performance and cause unexpected bugs. Possible "
+             "values: 0 - Normal, 1 - Above normal, 2 - High",
+             "General");
+
 namespace xe {
 using namespace xe::literals;
 
@@ -125,6 +131,13 @@ Emulator::Emulator(const std::filesystem::path& command_line,
       paused_(false),
       restoring_(false),
       restore_fence_() {
+  if (cvars::priority_class != 0) {
+    if (SetProcessPriorityClass(cvars::priority_class)) {
+      XELOGI("Higher priority class request: Successful. New priority: {}",
+             cvars::priority_class);
+    }
+  }
+
 #if XE_PLATFORM_WIN32 == 1
   // Show a disclaimer that links to the quickstart
   // guide the first time they ever open the emulator