1 files changed, 79 insertions, 0 deletions
diff --git a/hal/windows/WindowsProcessPriority.cpp b/hal/windows/WindowsProcessPriority.cpp
new file mode 100644
index 0000000000..fe9b78133b
--- /dev/null
+++ b/hal/windows/WindowsProcessPriority.cpp
@@ -0,0 +1,79 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "Hal.h"
+#include "HalLog.h"
+#include "nsWindowsHelpers.h"  // for nsAutoHandle and nsModuleHandle
+#include "mozilla/StaticPrefs_dom.h"
+
+#include <windows.h>
+
+using namespace mozilla::hal;
+
+namespace mozilla {
+namespace hal_impl {
+
+void SetProcessPriority(int aPid, ProcessPriority aPriority) {
+  HAL_LOG("WindowsProcessPriority - SetProcessPriority(%d, %s)\n", aPid,
+          ProcessPriorityToString(aPriority));
+
+  nsAutoHandle processHandle(
+      ::OpenProcess(PROCESS_SET_INFORMATION, FALSE, aPid));
+  if (processHandle) {
+    DWORD priority = NORMAL_PRIORITY_CLASS;
+    if (aPriority == PROCESS_PRIORITY_BACKGROUND) {
+      priority = IDLE_PRIORITY_CLASS;
+    } else if (aPriority == PROCESS_PRIORITY_BACKGROUND_PERCEIVABLE) {
+      priority = BELOW_NORMAL_PRIORITY_CLASS;
+    }
+
+    if (::SetPriorityClass(processHandle, priority)) {
+      HAL_LOG("WindowsProcessPriority - priority set to %d for pid %d\n",
+              aPriority, aPid);
+    }
+
+    // Set the process into or out of EcoQoS.
+    static bool alreadyInitialized = false;
+    static decltype(::SetProcessInformation)* setProcessInformation = nullptr;
+    if (!alreadyInitialized) {
+      if (aPriority == PROCESS_PRIORITY_PARENT_PROCESS ||
+          !StaticPrefs::dom_ipc_processPriorityManager_backgroundUsesEcoQoS()) {
+        return;
+      }
+
+      alreadyInitialized = true;
+      // SetProcessInformation only exists on Windows 8 and later.
+      nsModuleHandle module(LoadLibrary(L"Kernel32.dll"));
+      if (module) {
+        setProcessInformation =
+            (decltype(::SetProcessInformation)*)GetProcAddress(
+                module, "SetProcessInformation");
+      }
+    }
+    if (!setProcessInformation) {
+      return;
+    }
+
+    PROCESS_POWER_THROTTLING_STATE PowerThrottling;
+    RtlZeroMemory(&PowerThrottling, sizeof(PowerThrottling));
+    PowerThrottling.Version = PROCESS_POWER_THROTTLING_CURRENT_VERSION;
+    PowerThrottling.ControlMask = PROCESS_POWER_THROTTLING_EXECUTION_SPEED;
+    PowerThrottling.StateMask =
+        (aPriority == PROCESS_PRIORITY_BACKGROUND) &&
+                StaticPrefs::
+                    dom_ipc_processPriorityManager_backgroundUsesEcoQoS()
+            ? PROCESS_POWER_THROTTLING_EXECUTION_SPEED
+            : 0;
+    if (setProcessInformation(processHandle, ProcessPowerThrottling,
+                              &PowerThrottling, sizeof(PowerThrottling))) {
+      HAL_LOG("SetProcessInformation(%d, %s)\n", aPid,
+              aPriority == PROCESS_PRIORITY_BACKGROUND ? "eco" : "normal");
+    } else {
+      HAL_LOG("SetProcessInformation failed for %d\n", aPid);
+    }
+  }
+}
+
+}  // namespace hal_impl
+}  // namespace mozilla