Improve memory pressure reporting on Android.

This CL overhauls the way memory pressure is sensed and reported for
the browser process. Main changes are:

* ActivityManager.getMyMemoryStat() is used to poll pressure.

* Pressure signals are throttled.

* CRITICAL->MODERATE pressure changes are always reported.

See MemoryPressureMonitor.java comments for details.

Bug: 813909
Change-Id: I6fb5395b175cf8ca4ac40fac021125dd9d7fbc9f
Reviewed-on: https://chromium-review.googlesource.com/953166
Commit-Queue: Dmitry Skiba <dskiba@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549818}

android_webview/browser/aw_browser_main_parts.cc

@@ -95,7 +95,7 @@ int AwBrowserMainParts::PreCreateThreads() {
   pak_file_path = pak_file_path.AppendASCII("resources.pak");
   ui::LoadMainAndroidPackFile("assets/resources.pak", pak_file_path);
 
-  base::android::MemoryPressureListenerAndroid::RegisterSystemCallback(
+  base::android::MemoryPressureListenerAndroid::Initialize(
       base::android::AttachCurrentThread());
   breakpad::CrashDumpObserver::Create();
 

android_webview/glue/java/src/com/android/webview/chromium/SharedStatics.java

@@ -17,8 +17,8 @@ import org.chromium.android_webview.AwSettings;
 import org.chromium.android_webview.command_line.CommandLineUtil;
 import org.chromium.base.Callback;
 import org.chromium.base.MemoryPressureLevel;
-import org.chromium.base.MemoryPressureListener;
 import org.chromium.base.ThreadUtils;
+import org.chromium.base.memory.MemoryPressureMonitor;
 
 import java.util.List;
 
@@ -71,7 +71,7 @@ public class SharedStatics {
 
     public void freeMemoryForTests() {
         if (ActivityManager.isRunningInTestHarness()) {
-            MemoryPressureListener.onMemoryPressure(MemoryPressureLevel.CRITICAL);
+            MemoryPressureMonitor.INSTANCE.notifyPressure(MemoryPressureLevel.CRITICAL);
         }
     }
 

android_webview/java/src/org/chromium/android_webview/AwBrowserContext.java

@@ -7,6 +7,7 @@ package org.chromium.android_webview;
 import android.content.Context;
 import android.content.SharedPreferences;
 
+import org.chromium.base.memory.MemoryPressureMonitor;
 import org.chromium.content.browser.ContentViewStatics;
 
 /**
@@ -32,6 +33,20 @@ public class AwBrowserContext {
         mApplicationContext = applicationContext;
 
         PlatformServiceBridge.getInstance().setSafeBrowsingHandler();
+
+        // Register MemoryPressureMonitor callbacks and make sure it polls only if there is at
+        // least one WebView around.
+        MemoryPressureMonitor.INSTANCE.registerComponentCallbacks();
+        AwContentsLifecycleNotifier.addObserver(new AwContentsLifecycleNotifier.Observer() {
+            @Override
+            public void onFirstWebViewCreated() {
+                MemoryPressureMonitor.INSTANCE.enablePolling();
+            }
+            @Override
+            public void onLastWebViewDestroyed() {
+                MemoryPressureMonitor.INSTANCE.disablePolling();
+            }
+        });
     }
 
     public AwGeolocationPermissions getGeolocationPermissions() {

base/BUILD.gn

@@ -2740,6 +2740,8 @@ if (is_android) {
       "android/java/src/org/chromium/base/process_launcher/ChildProcessService.java",
       "android/java/src/org/chromium/base/process_launcher/ChildProcessServiceDelegate.java",
       "android/java/src/org/chromium/base/process_launcher/FileDescriptorInfo.java",
+      "android/java/src/org/chromium/base/memory/MemoryPressureMonitor.java",
+      "android/java/src/org/chromium/base/memory/MemoryPressureCallback.java",
     ]
 
     # New versions of BuildConfig.java and NativeLibraries.java
@@ -2773,7 +2775,6 @@ if (is_android) {
       "android/javatests/src/org/chromium/base/CommandLineInitUtilTest.java",
       "android/javatests/src/org/chromium/base/CommandLineTest.java",
       "android/javatests/src/org/chromium/base/EarlyTraceEventTest.java",
-      "android/javatests/src/org/chromium/base/MemoryPressureListenerTest.java",
 
       # TODO(nona): move to Junit once that is built for Android N.
       "android/javatests/src/org/chromium/base/LocaleUtilsTest.java",
@@ -2888,6 +2889,7 @@ if (is_android) {
       "android/junit/src/org/chromium/base/LogTest.java",
       "android/junit/src/org/chromium/base/NonThreadSafeTest.java",
       "android/junit/src/org/chromium/base/PromiseTest.java",
+      "android/junit/src/org/chromium/base/memory/MemoryPressureMonitorTest.java",
       "android/junit/src/org/chromium/base/process_launcher/ChildConnectionAllocatorTest.java",
       "android/junit/src/org/chromium/base/process_launcher/ChildProcessConnectionTest.java",
       "test/android/junit/src/org/chromium/base/test/SetUpStatementTest.java",

base/android/java/src/org/chromium/base/MemoryPressureListener.java

@@ -6,16 +6,23 @@ package org.chromium.base;
 
 import android.app.Activity;
 import android.content.ComponentCallbacks2;
-import android.content.res.Configuration;
 
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.base.annotations.MainDex;
-
+import org.chromium.base.memory.MemoryPressureCallback;
 
 /**
- * This is an internal implementation of the C++ counterpart.
- * It registers a ComponentCallbacks2 with the system, and dispatches into
- * native for levels that are considered actionable.
+ * This class is Java equivalent of base::MemoryPressureListener: it distributes pressure
+ * signals to callbacks.
+ *
+ * The class also serves as an entry point to the native side - once native code is ready,
+ * it adds native callback.
+ *
+ * notifyMemoryPressure() is called exclusively by MemoryPressureMonitor, which
+ * monitors and throttles pressure signals.
+ *
+ * NOTE: this class should only be used on UiThread as defined by ThreadUtils (which is
+ *       Android main thread for Chrome, but can be some other thread for WebView).
  */
 @MainDex
 public class MemoryPressureListener {
@@ -45,57 +52,41 @@ public class MemoryPressureListener {
     private static final String ACTION_TRIM_MEMORY_MODERATE =
             "org.chromium.base.ACTION_TRIM_MEMORY_MODERATE";
 
-    private static OnMemoryPressureCallbackForTesting sOnMemoryPressureCallbackForTesting;
+    private static final ObserverList<MemoryPressureCallback> sCallbacks = new ObserverList<>();
 
-    @VisibleForTesting
+    /**
+     * Called by the native side to add native callback.
+     */
     @CalledByNative
-    public static void registerSystemCallback() {
-        ContextUtils.getApplicationContext().registerComponentCallbacks(
-                new ComponentCallbacks2() {
-                    @Override
-                    public void onTrimMemory(int level) {
-                        if (level >= ComponentCallbacks2.TRIM_MEMORY_COMPLETE
-                                || level == ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL) {
-                            onMemoryPressure(MemoryPressureLevel.CRITICAL);
-                        } else if (level >= ComponentCallbacks2.TRIM_MEMORY_BACKGROUND) {
-                            // Don't notifiy on TRIM_MEMORY_UI_HIDDEN, since this class only
-                            // dispatches actionable memory pressure signals to native.
-                            onMemoryPressure(MemoryPressureLevel.MODERATE);
-                        }
-                    }
-
-                    @Override
-                    public void onLowMemory() {
-                        onMemoryPressure(MemoryPressureLevel.CRITICAL);
-                    }
-
-                    @Override
-                    public void onConfigurationChanged(Configuration configuration) {
-                    }
-                });
+    private static void addNativeCallback() {
+        addCallback(MemoryPressureListener::nativeOnMemoryPressure);
     }
 
-    /** Memory pressure callback that is called before calling native. Use for testing only.
+    /**
+     * Adds a memory pressure callback.
+     * Callback is only added once, regardless of the number of addCallback() calls.
+     * This method should be called only on ThreadUtils.UiThread.
      */
-    @VisibleForTesting
-    @FunctionalInterface
-    public interface OnMemoryPressureCallbackForTesting {
-        public void apply(@MemoryPressureLevel int pressure);
+    public static void addCallback(MemoryPressureCallback callback) {
+        sCallbacks.addObserver(callback);
     }
 
-    @VisibleForTesting
-    public static void setOnMemoryPressureCallbackForTesting(
-            OnMemoryPressureCallbackForTesting callback) {
-        sOnMemoryPressureCallbackForTesting = callback;
+    /**
+     * Removes previously added memory pressure callback.
+     * This method should be called only on ThreadUtils.UiThread.
+     */
+    public void removeCallback(MemoryPressureCallback callback) {
+        sCallbacks.removeObserver(callback);
     }
 
-    /** Reports memory pressure.
+    /**
+     * Distributes |pressure| to all callbacks.
+     * This method should be called only on ThreadUtils.UiThread.
      */
-    public static void onMemoryPressure(@MemoryPressureLevel int pressure) {
-        if (sOnMemoryPressureCallbackForTesting != null) {
-            sOnMemoryPressureCallbackForTesting.apply(pressure);
+    public static void notifyMemoryPressure(@MemoryPressureLevel int pressure) {
+        for (MemoryPressureCallback callback : sCallbacks) {
+            callback.onPressure(pressure);
         }
-        nativeOnMemoryPressure(pressure);
     }
 
     /**
@@ -135,6 +126,5 @@ public class MemoryPressureListener {
         activity.onTrimMemory(level);
     }
 
-    // Don't call directly, always go through onMemoryPressure().
     private static native void nativeOnMemoryPressure(@MemoryPressureLevel int pressure);
 }

base/android/java/src/org/chromium/base/memory/MemoryPressureCallback.java

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.base.memory;
+
+import org.chromium.base.MemoryPressureLevel;
+
+/**
+ * Memory pressure callback interface.
+ */
+@FunctionalInterface
+public interface MemoryPressureCallback {
+    public void onPressure(@MemoryPressureLevel int pressure);
+}

base/android/javatests/src/org/chromium/base/MemoryPressureListenerTest.java

-// Copyright 2018 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package org.chromium.base;
-
-import android.app.Application;
-import android.content.ComponentCallbacks2;
-import android.support.test.filters.SmallTest;
-
-import org.junit.Assert;
-import org.junit.Before;
-import org.junit.Test;
-import org.junit.runner.RunWith;
-
-import org.chromium.base.library_loader.LibraryLoader;
-import org.chromium.base.library_loader.LibraryProcessType;
-import org.chromium.base.test.BaseJUnit4ClassRunner;
-
-/**
- * Tests for {@link MemoryPressureListener}.
- */
-@RunWith(BaseJUnit4ClassRunner.class)
-public class MemoryPressureListenerTest {
-    /** Helper class to capture and validate OnMemoryPressureCallback calls.
-     */
-    private static class MemoryPressureCallback {
-        private boolean mCalled;
-        private @MemoryPressureLevel int mPressure = MemoryPressureLevel.NONE;
-
-        public void install() {
-            MemoryPressureListener.setOnMemoryPressureCallbackForTesting(this::onMemoryPressure);
-        }
-
-        public void uninstall() {
-            MemoryPressureListener.setOnMemoryPressureCallbackForTesting(null);
-        }
-
-        private void onMemoryPressure(@MemoryPressureLevel int pressure) {
-            Assert.assertFalse("Should not be called twice", mCalled);
-            mCalled = true;
-            mPressure = pressure;
-        }
-
-        public void assertCalledWith(@MemoryPressureLevel int pressure) {
-            Assert.assertTrue(mCalled);
-            Assert.assertEquals(pressure, mPressure);
-        }
-
-        public void assertNotCalled() {
-            Assert.assertFalse(mCalled);
-        }
-    }
-
-    @Before
-    public void setUp() throws Exception {
-        LibraryLoader.get(LibraryProcessType.PROCESS_BROWSER).ensureInitialized();
-        MemoryPressureListener.registerSystemCallback();
-    }
-
-    @Test
-    @SmallTest
-    public void testLowMemoryTranslation() {
-        MemoryPressureCallback callback = new MemoryPressureCallback();
-        ThreadUtils.runOnUiThreadBlocking(() -> {
-            callback.install();
-            ((Application) ContextUtils.getApplicationContext()).onLowMemory();
-            callback.uninstall();
-        });
-        callback.assertCalledWith(MemoryPressureLevel.CRITICAL);
-    }
-
-    @Test
-    @SmallTest
-    public void testTrimLevelTranslation() {
-        Integer[][] trimLevelToPressureMap = {
-                // Levels >= TRIM_MEMORY_COMPLETE map to CRITICAL.
-                {ComponentCallbacks2.TRIM_MEMORY_COMPLETE + 1, MemoryPressureLevel.CRITICAL},
-                {ComponentCallbacks2.TRIM_MEMORY_COMPLETE, MemoryPressureLevel.CRITICAL},
-
-                // TRIM_MEMORY_RUNNING_CRITICAL maps to CRITICAL.
-                {ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL, MemoryPressureLevel.CRITICAL},
-
-                // Levels < TRIM_MEMORY_COMPLETE && >= TRIM_MEMORY_BACKGROUND map to MODERATE.
-                {ComponentCallbacks2.TRIM_MEMORY_COMPLETE - 1, MemoryPressureLevel.MODERATE},
-                {ComponentCallbacks2.TRIM_MEMORY_BACKGROUND + 1, MemoryPressureLevel.MODERATE},
-                {ComponentCallbacks2.TRIM_MEMORY_BACKGROUND, MemoryPressureLevel.MODERATE},
-
-                // Other levels don't trigger memory pressure at all.
-                {ComponentCallbacks2.TRIM_MEMORY_BACKGROUND - 1, null},
-                {ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW, null},
-                {ComponentCallbacks2.TRIM_MEMORY_RUNNING_MODERATE, null},
-                {ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN, null}};
-        for (Integer[] trimLevelAndPressure : trimLevelToPressureMap) {
-            final int trimLevel = trimLevelAndPressure[0];
-            Integer pressure = trimLevelAndPressure[1];
-            MemoryPressureCallback callback = new MemoryPressureCallback();
-            ThreadUtils.runOnUiThreadBlocking(() -> {
-                callback.install();
-                ((Application) ContextUtils.getApplicationContext()).onTrimMemory(trimLevel);
-                callback.uninstall();
-            });
-            if (pressure == null) {
-                callback.assertNotCalled();
-            } else {
-                callback.assertCalledWith(pressure);
-            }
-        }
-    }
-}

base/android/memory_pressure_listener_android.cc

@@ -22,8 +22,8 @@ static void JNI_MemoryPressureListener_OnMemoryPressure(
 namespace base {
 namespace android {
 
-void MemoryPressureListenerAndroid::RegisterSystemCallback(JNIEnv* env) {
-  Java_MemoryPressureListener_registerSystemCallback(env);
+void MemoryPressureListenerAndroid::Initialize(JNIEnv* env) {
+  Java_MemoryPressureListener_addNativeCallback(env);
 }
 
 }  // namespace android

base/android/memory_pressure_listener_android.h

@@ -14,7 +14,7 @@ namespace android {
 // Implements the C++ counter part of MemoryPressureListener.java
 class BASE_EXPORT MemoryPressureListenerAndroid {
  public:
-  static void RegisterSystemCallback(JNIEnv* env);
+  static void Initialize(JNIEnv* env);
 
   // Called by JNI.
   static void OnMemoryPressure(int memory_pressure_type);

chrome/android/java/src/org/chromium/chrome/browser/ChromeApplication.java

@@ -11,6 +11,7 @@ import android.content.Intent;
 import android.os.Bundle;
 
 import org.chromium.base.ActivityState;
+import org.chromium.base.ApplicationState;
 import org.chromium.base.ApplicationStatus;
 import org.chromium.base.BuildConfig;
 import org.chromium.base.CommandLineInitUtil;
@@ -22,6 +23,7 @@ import org.chromium.base.ThreadUtils;
 import org.chromium.base.TraceEvent;
 import org.chromium.base.annotations.MainDex;
 import org.chromium.base.library_loader.ProcessInitException;
+import org.chromium.base.memory.MemoryPressureMonitor;
 import org.chromium.base.multidex.ChromiumMultiDexInstaller;
 import org.chromium.build.BuildHooks;
 import org.chromium.build.BuildHooksAndroid;
@@ -92,10 +94,21 @@ public class ChromeApplication extends Application {
             // Only browser process requires custom resources.
             BuildHooksAndroid.initCustomResources(this);
 
+            // Disable MemoryPressureMonitor polling when Chrome goes to the background.
+            ApplicationStatus.registerApplicationStateListener(newState -> {
+                if (newState == ApplicationState.HAS_RUNNING_ACTIVITIES) {
+                    MemoryPressureMonitor.INSTANCE.enablePolling();
+                } else if (newState == ApplicationState.HAS_STOPPED_ACTIVITIES) {
+                    MemoryPressureMonitor.INSTANCE.disablePolling();
+                }
+            });
+
             // Not losing much to not cover the below conditional since it just has simple setters.
             TraceEvent.end("ChromeApplication.attachBaseContext");
         }
 
+        MemoryPressureMonitor.INSTANCE.registerComponentCallbacks();
+
         if (!ContextUtils.isIsolatedProcess()) {
             // Incremental install disables process isolation, so things in this block will actually
             // be run for incremental apks, but not normal apks.

chrome/browser/browser_process_platform_part_android.cc

@@ -8,7 +8,7 @@
 #include "chrome/browser/lifetime/application_lifetime_android.h"
 
 BrowserProcessPlatformPart::BrowserProcessPlatformPart() {
-  base::android::MemoryPressureListenerAndroid::RegisterSystemCallback(
+  base::android::MemoryPressureListenerAndroid::Initialize(
       base::android::AttachCurrentThread());
 }
 

content/app/android/content_child_process_service_delegate.cc

@@ -114,7 +114,7 @@ void JNI_ContentChildProcessServiceDelegate_InternalInitChildProcess(
   gpu::ScopedSurfaceRequestConduit::SetInstance(
       g_child_process_surface_manager.Pointer());
 
-  base::android::MemoryPressureListenerAndroid::RegisterSystemCallback(env);
+  base::android::MemoryPressureListenerAndroid::Initialize(env);
 }
 
 }  // namespace

tools/metrics/histograms/histograms.xml

@@ -1345,6 +1345,24 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Android.MemoryPressureMonitor.GetMyMemoryState.Failed.Time"
+    units="microseconds">
+  <owner>dskiba@chromium.org</owner>
+  <summary>
+    The duration of each failed ActivityManager.getMyMemoryState() call made by
+    MemoryPressureMonitor.
+  </summary>
+</histogram>
+
+<histogram name="Android.MemoryPressureMonitor.GetMyMemoryState.Succeeded.Time"
+    units="microseconds">
+  <owner>dskiba@chromium.org</owner>
+  <summary>
+    The duration of each successful ActivityManager.getMyMemoryState() call made
+    by MemoryPressureMonitor.
+  </summary>
+</histogram>
+
 <histogram name="Android.ModerateBindingCount" units="bindings">
   <owner>jaekyun@chromium.org</owner>
   <summary>