Bug 1753700 - Add priorityHint to allow apps to increase process priority for background tabs r=geckoview-reviewers,mccr8,agi

Prior behavior for active tabs in an inactive app would have the process priority oom score of 15. Now it's set to a higher priority oom score of 11. This will increase priority for recently used tabs on apps and prevent Android from unloading them.

Differential Revision: https://phabricator.services.mozilla.com/D142386

dom/interfaces/base/nsIRemoteTab.idl

@@ -25,6 +25,12 @@ interface nsIRemoteTab : nsISupports
    */
   readonly attribute boolean hasLayers;
 
+  /**
+   * When set to true, this priority hint indicates that the content
+   * processes of this tab should be set to a higher process priority.
+   */
+  attribute boolean priorityHint;
+
   /**
    * Adjusts the tab's active state in the process priority manager,
    * allowing its process to be given a lower priority.

dom/ipc/BrowserHost.cpp

@@ -119,8 +119,11 @@ BrowserHost::SetRenderLayers(bool aRenderLayers) {
   if (!mRoot) {
     return NS_OK;
   }
+
+  bool priorityHint;
+  GetPriorityHint(&priorityHint);
   ProcessPriorityManager::BrowserPriorityChanged(
-      GetBrowsingContext()->Canonical(), aRenderLayers);
+      GetBrowsingContext()->Canonical(), priorityHint || aRenderLayers);
   mRoot->SetRenderLayers(aRenderLayers);
   return NS_OK;
 }
@@ -136,6 +139,30 @@ BrowserHost::GetHasLayers(bool* aHasLayers) {
   return NS_OK;
 }
 
+/* attribute boolean priorityHint; */
+NS_IMETHODIMP
+BrowserHost::SetPriorityHint(bool aPriorityHint) {
+  if (!mRoot) {
+    return NS_OK;
+  }
+  bool renderLayers;
+  GetRenderLayers(&renderLayers);
+  ProcessPriorityManager::BrowserPriorityChanged(
+      GetBrowsingContext()->Canonical(), aPriorityHint || renderLayers);
+  mRoot->SetPriorityHint(aPriorityHint);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserHost::GetPriorityHint(bool* aPriorityHint) {
+  if (!mRoot) {
+    *aPriorityHint = false;
+    return NS_OK;
+  }
+  *aPriorityHint = mRoot->GetPriorityHint();
+  return NS_OK;
+}
+
 /* void resolutionChanged (); */
 NS_IMETHODIMP
 BrowserHost::NotifyResolutionChanged(void) {

dom/ipc/BrowserParent.cpp

@@ -231,6 +231,7 @@ BrowserParent::BrowserParent(ContentParent* aManager, const TabId& aTabId,
       mRemoteTargetSetsCursor(false),
       mIsPreservingLayers(false),
       mRenderLayers(true),
+      mPriorityHint(false),
       mHasLayers(false),
       mHasPresented(false),
       mIsReadyToHandleInputEvents(false),
@@ -3477,6 +3478,12 @@ void BrowserParent::SetRenderLayersInternal(bool aEnabled) {
   }
 }
 
+bool BrowserParent::GetPriorityHint() { return mPriorityHint; }
+
+void BrowserParent::SetPriorityHint(bool aPriorityHint) {
+  mPriorityHint = aPriorityHint;
+}
+
 void BrowserParent::PreserveLayers(bool aPreserveLayers) {
   if (mIsPreservingLayers == aPreserveLayers) {
     return;

dom/ipc/BrowserParent.h

@@ -706,6 +706,8 @@ class BrowserParent final : public PBrowserParent,
   bool GetHasLayers();
   bool GetRenderLayers();
   void SetRenderLayers(bool aRenderLayers);
+  bool GetPriorityHint();
+  void SetPriorityHint(bool aPriorityHint);
   void PreserveLayers(bool aPreserveLayers);
   void NotifyResolutionChanged();
 
@@ -963,6 +965,9 @@ class BrowserParent final : public PBrowserParent,
   // and have uploaded - for that, use mHasLayers.
   bool mRenderLayers : 1;
 
+  // True if process should be set to a higher priority.
+  bool mPriorityHint : 1;
+
   // True if the compositor has reported that the BrowserChild has uploaded
   // layers.
   bool mHasLayers : 1;

dom/ipc/ProcessPriorityManager.cpp

@@ -336,7 +336,7 @@ class ParticularProcessPriorityManager final : public WakeLockObserver,
 
   nsCOMPtr<nsITimer> mResetPriorityTimer;
 
-  // This hashtable contains the list of active TabId for this process.
+  // This hashtable contains the list of high priority TabIds for this process.
   nsTHashSet<uint64_t> mHighPriorityBrowserParents;
 };
 

dom/ipc/ProcessPriorityManager.h

@@ -73,7 +73,7 @@ class ProcessPriorityManager final {
 
   /**
    * Updates the contents of mHighPriorityBrowserParents to keep track of
-   * the list of TabIds for this process that are active.
+   * the list of TabIds for this process that are high priority.
    */
   static void BrowserPriorityChanged(dom::CanonicalBrowsingContext* aBC,
                                      bool aPriority);

dom/ipc/tests/browser_ProcessPriorityManager.js

@@ -286,8 +286,9 @@ async function assertPriorityChangeOnBackground({
 
 /**
  * Test that if a normal tab goes into the background,
- * it has its process priority lowered to
- * PROCESS_PRIORITY_BACKGROUND.
+ * it has its process priority lowered to PROCESS_PRIORITY_BACKGROUND.
+ * Additionally, test priorityHint flag sets the process priority
+ * appropriately to PROCESS_PRIORITY_BACKGROUND and PROCESS_PRIORITY_FOREGROUND.
  */
 add_task(async function test_normal_background_tab() {
   let originalTab = gBrowser.selectedTab;
@@ -307,6 +308,62 @@ add_task(async function test_normal_background_tab() {
         toTab: tab,
         fromTabExpectedPriority: PROCESS_PRIORITY_BACKGROUND,
       });
+
+      let origtabID = browsingContextChildID(
+        originalTab.linkedBrowser.browsingContext
+      );
+      Assert.equal(
+        originalTab.linkedBrowser.frameLoader.remoteTab.priorityHint,
+        false,
+        "PriorityHint of the original tab should be false on default"
+      );
+
+      // Test when priorityHint is true, the original tab priority
+      // becomes PROCESS_PRIORITY_FOREGROUND.
+      originalTab.linkedBrowser.frameLoader.remoteTab.priorityHint = true;
+      Assert.equal(
+        gTabPriorityWatcher.currentPriority(origtabID),
+        PROCESS_PRIORITY_FOREGROUND,
+        "Setting priorityHint to true should set the original tab to foreground priority"
+      );
+
+      // Test when priorityHint is false, the original tab priority
+      // becomes PROCESS_PRIORITY_BACKGROUND.
+      originalTab.linkedBrowser.frameLoader.remoteTab.priorityHint = false;
+      await new Promise(resolve =>
+        // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+        setTimeout(resolve, WAIT_FOR_CHANGE_TIME_MS)
+      );
+      Assert.equal(
+        gTabPriorityWatcher.currentPriority(origtabID),
+        PROCESS_PRIORITY_BACKGROUND,
+        "Setting priorityHint to false should set the original tab to background priority"
+      );
+
+      let tabID = browsingContextChildID(tab.linkedBrowser.browsingContext);
+      Assert.equal(
+        tab.linkedBrowser.frameLoader.remoteTab.priorityHint,
+        false,
+        "PriorityHint of the active tab should be false on default"
+      );
+
+      // Test when priorityHint is true, the process priority of the
+      // active tab remains PROCESS_PRIORITY_FOREGROUND.
+      tab.linkedBrowser.frameLoader.remoteTab.priorityHint = true;
+      Assert.equal(
+        gTabPriorityWatcher.currentPriority(tabID),
+        PROCESS_PRIORITY_FOREGROUND,
+        "Setting priorityHint to true should maintain the new tab priority as foreground"
+      );
+
+      // Test when priorityHint is false, the process priority of the
+      // active tab remains PROCESS_PRIORITY_FOREGROUND.
+      tab.linkedBrowser.frameLoader.remoteTab.priorityHint = false;
+      Assert.equal(
+        gTabPriorityWatcher.currentPriority(tabID),
+        PROCESS_PRIORITY_FOREGROUND,
+        "Setting priorityHint to false should maintain the new tab priority as foreground"
+      );
     }
   );
 });

mobile/android/modules/geckoview/GeckoViewWebExtension.jsm

@@ -544,6 +544,9 @@ class MobileWindowTracker extends EventEmitter {
   setTabActive(aWindow, aActive) {
     const { browser, tab, docShell } = aWindow;
     tab.active = aActive;
+    if (browser.frameLoader.remoteTab) {
+      browser.frameLoader.remoteTab.priorityHint = aActive;
+    }
 
     if (aActive) {
       this._topWindow = Cu.getWeakReference(aWindow);