From c2d02b522cd7efea659a3ff784040f84b8cdbc18 Mon Sep 17 00:00:00 2001
From: Olivier Gaillard <gaillard@google.com>
Date: Thu, 20 Sep 2018 13:53:18 +0100
Subject: [PATCH] Use the background thread instead ActivityManager to update
 CPU stats.

Updating the CPU stats can be quite slow and blocks the ActivityManager
handler thread.

Bug: 115506775
Change-Id: I9f67acfe2724c11d117703b2c4ccdbcc1f61c5ab
Test: manual - dumpsys batterystats | grep CPU
---
 core/java/com/android/internal/os/BatteryStatsImpl.java        | 3 +++
 .../java/com/android/server/am/ActivityManagerService.java     | 3 ++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/core/java/com/android/internal/os/BatteryStatsImpl.java b/core/java/com/android/internal/os/BatteryStatsImpl.java
index 31f13c33c1678..33b9ff7cee4f1 100644
--- a/core/java/com/android/internal/os/BatteryStatsImpl.java
+++ b/core/java/com/android/internal/os/BatteryStatsImpl.java
@@ -337,6 +337,9 @@ public class BatteryStatsImpl extends BatteryStats {
 
     private final PlatformIdleStateCallback mPlatformIdleStateCallback;
 
+    /**
+     * This handler is running on {@link BackgroundThread}.
+     */
     final class MyHandler extends Handler {
         public MyHandler(Looper looper) {
             super(looper, null, true);
diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index 6e90d5b5c21b4..692f9cfaa833b 100644
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -2381,7 +2381,8 @@ public class ActivityManagerService extends IActivityManager.Stub
         final File systemDir = SystemServiceManager.ensureSystemDir();
 
         // TODO: Move creation of battery stats service outside of activity manager service.
-        mBatteryStatsService = new BatteryStatsService(systemContext, systemDir, mHandler);
+        mBatteryStatsService = new BatteryStatsService(systemContext, systemDir,
+                BackgroundThread.get().getHandler());
         mBatteryStatsService.getActiveStatistics().readLocked();
         mBatteryStatsService.scheduleWriteToDisk();
         mOnBattery = DEBUG_POWER ? true