1 files changed, 74 insertions, 0 deletions
diff --git a/mobile/android/geckoview/src/main/java/org/mozilla/gecko/process/MemoryController.java b/mobile/android/geckoview/src/main/java/org/mozilla/gecko/process/MemoryController.java
new file mode 100644
index 0000000000..f2dcb7a52b
--- /dev/null
+++ b/mobile/android/geckoview/src/main/java/org/mozilla/gecko/process/MemoryController.java
@@ -0,0 +1,74 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.gecko.process;
+
+import android.content.ComponentCallbacks2;
+import android.content.res.Configuration;
+import android.util.Log;
+import androidx.annotation.NonNull;
+import org.mozilla.gecko.GeckoAppShell;
+
+public class MemoryController implements ComponentCallbacks2 {
+  private static final String LOGTAG = "MemoryController";
+  private long mLastLowMemoryNotificationTime = 0;
+
+  // Allowed elapsed time between full GCs while under constant memory pressure
+  private static final long LOW_MEMORY_ONGOING_RESET_TIME_MS = 10000;
+
+  private static final int LOW = 0;
+  private static final int MODERATE = 1;
+  private static final int CRITICAL = 2;
+
+  private int memoryLevelFromTrim(final int level) {
+    if (level >= ComponentCallbacks2.TRIM_MEMORY_COMPLETE
+        || level == ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL) {
+      return CRITICAL;
+    } else if (level >= ComponentCallbacks2.TRIM_MEMORY_BACKGROUND) {
+      return MODERATE;
+    }
+    return LOW;
+  }
+
+  public void onTrimMemory(final int level) {
+    Log.i(LOGTAG, "onTrimMemory(" + level + ")");
+    onMemoryNotification(memoryLevelFromTrim(level));
+  }
+
+  @Override
+  public void onConfigurationChanged(final @NonNull Configuration newConfig) {}
+
+  public void onLowMemory() {
+    Log.i(LOGTAG, "onLowMemory");
+    onMemoryNotification(CRITICAL);
+  }
+
+  private void onMemoryNotification(final int level) {
+    if (level == LOW) {
+      // The trim level is too low to be actionable
+      return;
+    }
+
+    // See nsIMemory.idl for descriptions of the various arguments to the "memory-pressure"
+    // observer.
+    final String observerArg;
+
+    final long currentNotificationTime = System.currentTimeMillis();
+    if (level == CRITICAL
+        || (currentNotificationTime - mLastLowMemoryNotificationTime)
+            >= LOW_MEMORY_ONGOING_RESET_TIME_MS) {
+      // We do a full "low-memory" notification for both new and last-ditch onTrimMemory requests.
+      observerArg = "low-memory";
+      mLastLowMemoryNotificationTime = currentNotificationTime;
+    } else {
+      // If it has been less than ten seconds since the last time we sent a "low-memory"
+      // notification, we send a "low-memory-ongoing" notification instead.
+      // This prevents Gecko from re-doing full GC's repeatedly over and over in succession,
+      // as they are expensive and quickly result in diminishing returns.
+      observerArg = "low-memory-ongoing";
+    }
+
+    GeckoAppShell.notifyObservers("memory-pressure", observerArg);
+  }
+}