From c9dc3ae6fd924a0a1e29325d87edcd8d3316c0ad Mon Sep 17 00:00:00 2001
From: Brian Nicholson <bnicholson@mozilla.com>
Date: Tue, 1 Oct 2013 12:55:00 -0700
Subject: [PATCH] Bug 897162 - Lower Gecko thread priority when showing Top
 Sites page. r=lucasr

---
 mobile/android/base/home/TopSitesPage.java | 15 +++++++++
 mobile/android/base/util/ThreadUtils.java  | 36 ++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/mobile/android/base/home/TopSitesPage.java b/mobile/android/base/home/TopSitesPage.java
index af0a638785b..04c38e206f1 100644
--- a/mobile/android/base/home/TopSitesPage.java
+++ b/mobile/android/base/home/TopSitesPage.java
@@ -108,6 +108,9 @@ public class TopSitesPage extends HomeFragment {
     // Max number of entries shown in the grid from the cursor.
     private int mMaxGridEntries;
 
+    // Time in ms until the Gecko thread is reset to normal priority.
+    private static final long PRIORITY_RESET_TIMEOUT = 10000;
+
     /**
      *  Class to hold the bitmap of cached thumbnails/favicons.
      */
@@ -359,6 +362,14 @@ public class TopSitesPage extends HomeFragment {
     @Override
     protected void load() {
         getLoaderManager().initLoader(LOADER_ID_TOP_SITES, null, mCursorLoaderCallbacks);
+
+        // Since this is the primary fragment that loads whenever about:home is
+        // visited, we want to load it as quickly as possible. Heavy load on
+        // the Gecko thread can slow down the time it takes for thumbnails to
+        // appear, especially during startup (bug 897162). By minimizing the
+        // Gecko thread priority, we ensure that the UI appears quickly. The
+        // priority is reset to normal once thumbnails are loaded.
+        ThreadUtils.reduceGeckoPriority(PRIORITY_RESET_TIMEOUT);
     }
 
     /**
@@ -769,6 +780,10 @@ public class TopSitesPage extends HomeFragment {
             if (mGridAdapter != null) {
                 mGridAdapter.updateThumbnails(thumbnails);
             }
+
+            // Once thumbnails have finished loading, the UI is ready. Reset
+            // Gecko to normal priority.
+            ThreadUtils.resetGeckoPriority();
         }
 
         @Override
diff --git a/mobile/android/base/util/ThreadUtils.java b/mobile/android/base/util/ThreadUtils.java
index 11416567611..dc9a1d3600a 100644
--- a/mobile/android/base/util/ThreadUtils.java
+++ b/mobile/android/base/util/ThreadUtils.java
@@ -27,6 +27,9 @@ public final class ThreadUtils {
     public static MessageQueue sGeckoQueue;
     public static Thread sGeckoThread;
 
+    // Delayed Runnable that resets the Gecko thread priority.
+    private static volatile Runnable sPriorityResetRunnable;
+
     @SuppressWarnings("serial")
     public static class UiThreadBlockedException extends RuntimeException {
         public UiThreadBlockedException() {
@@ -127,4 +130,37 @@ public final class ThreadUtils {
     public static boolean isOnThread(Thread thread) {
         return (Thread.currentThread().getId() == thread.getId());
     }
+
+    /**
+     * Reduces the priority of the Gecko thread, allowing other operations
+     * (such as those related to the UI and database) to take precedence.
+     *
+     * Note that there are no guards in place to prevent multiple calls
+     * to this method from conflicting with each other.
+     *
+     * @param timeout Timeout in ms after which the priority will be reset
+     */
+    public static void reduceGeckoPriority(long timeout) {
+        sGeckoThread.setPriority(Thread.MIN_PRIORITY);
+        sPriorityResetRunnable = new Runnable() {
+            @Override
+            public void run() {
+                resetGeckoPriority();
+            }
+        };
+        getUiHandler().postDelayed(sPriorityResetRunnable, timeout);
+    }
+
+    /**
+     * Resets the priority of a thread whose priority has been reduced
+     * by reduceGeckoPriority.
+     */
+    public static void resetGeckoPriority() {
+        if (sPriorityResetRunnable != null) {
+            sGeckoThread.setPriority(Thread.NORM_PRIORITY);
+
+            getUiHandler().removeCallbacks(sPriorityResetRunnable);
+            sPriorityResetRunnable = null;
+        }
+    }
 }