From 5fa7fb1d9f2a5b078405c5a63fd7ad05115d71d6 Mon Sep 17 00:00:00 2001
From: Jesse Hall <jessehall@google.com>
Date: Thu, 19 Jan 2017 17:59:08 -0800
Subject: [PATCH] Load EGL early in Activity launch, instead of in Zygote

Preloading EGL in Zygote was originally a memory footprint
optimization, but it turns out to be an important app startup time
optimization as well. Preloading EGL in Zygote is incompatible with
updatable graphics drivers, but we don't want to do it on-demand as
part of drawing the first frame either, since that increases
first-frame latency unacceptably.

This change removes Zygote preload, and instead loads EGL on a
low-priority background thread immediately after choosing which
graphics driver to use. This means it is usually done well before
drawing the first frame, without significantly disrupting other
activity launch work.

Test: observe systrace of Calculator launch on bullhead
Bug: 34404021
Change-Id: I887aa09bd35b088b16f53a89838a0c7c98f15761
---
 core/java/android/os/GraphicsEnvironment.java  | 18 ++++++++++++++++++
 .../com/android/internal/os/ZygoteInit.java    | 10 ----------
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/core/java/android/os/GraphicsEnvironment.java b/core/java/android/os/GraphicsEnvironment.java
index 4b130ed1adc8a..20de370fa3445 100644
--- a/core/java/android/os/GraphicsEnvironment.java
+++ b/core/java/android/os/GraphicsEnvironment.java
@@ -19,6 +19,7 @@ package android.os;
 import android.content.Context;
 import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageManager;
+import android.opengl.EGL14;
 import android.os.SystemProperties;
 import android.util.Log;
 
@@ -34,6 +35,23 @@ public final class GraphicsEnvironment {
     private static final String PROPERTY_GFX_DRIVER = "ro.gfx.driver.0";
 
     public static void setupGraphicsEnvironment(Context context) {
+        chooseDriver(context);
+
+        // Now that we've figured out which driver to use for this process, load and initialize it.
+        // This can take multiple frame periods, and it would otherwise happen as part of the first
+        // frame, increasing first-frame latency. Starting it here, as a low-priority background
+        // thread, means that it's usually done long before we start drawing the first frame,
+        // without significantly disrupting other activity launch work.
+        Thread eglInitThread = new Thread(
+                () -> {
+                    Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
+                    EGL14.eglGetDisplay(EGL14.EGL_DEFAULT_DISPLAY);
+                },
+                "EGL Init");
+        eglInitThread.start();
+    }
+
+    private static void chooseDriver(Context context) {
         String driverPackageName = SystemProperties.get(PROPERTY_GFX_DRIVER);
         if (driverPackageName == null || driverPackageName.isEmpty()) {
             return;
diff --git a/core/java/com/android/internal/os/ZygoteInit.java b/core/java/com/android/internal/os/ZygoteInit.java
index ef5231cb6ff37..6ad7667dbdd66 100644
--- a/core/java/com/android/internal/os/ZygoteInit.java
+++ b/core/java/com/android/internal/os/ZygoteInit.java
@@ -25,7 +25,6 @@ import android.icu.impl.CacheValue;
 import android.icu.text.DecimalFormatSymbols;
 import android.icu.util.ULocale;
 import android.net.LocalServerSocket;
-import android.opengl.EGL14;
 import android.os.IInstalld;
 import android.os.Process;
 import android.os.RemoteException;
@@ -121,9 +120,6 @@ public class ZygoteInit {
         Trace.traceBegin(Trace.TRACE_TAG_DALVIK, "PreloadResources");
         preloadResources();
         Trace.traceEnd(Trace.TRACE_TAG_DALVIK);
-        Trace.traceBegin(Trace.TRACE_TAG_DALVIK, "PreloadOpenGL");
-        preloadOpenGL();
-        Trace.traceEnd(Trace.TRACE_TAG_DALVIK);
         preloadSharedLibraries();
         preloadTextResources();
         // Ask the WebViewFactory to do any initialization that must run in the zygote process,
@@ -164,12 +160,6 @@ public class ZygoteInit {
         System.loadLibrary("jnigraphics");
     }
 
-    private static void preloadOpenGL() {
-        if (!SystemProperties.getBoolean(PROPERTY_DISABLE_OPENGL_PRELOADING, false)) {
-            EGL14.eglGetDisplay(EGL14.EGL_DEFAULT_DISPLAY);
-        }
-    }
-
     private static void preloadTextResources() {
         Hyphenator.init();
         TextView.preloadFontCache();