Add sampling to FGS atom (2c7fdfcf) · Commits · e / os / android_frameworks_base

services/core/java/com/android/server/am/ActiveServices.java

+4 −0

Original line number	Diff line number	Diff line
		@@ -5904,6 +5904,10 @@ public final class ActiveServices {
		* @param durationMs Only meaningful for EXIT event, the duration from ENTER and EXIT state.
		*/
		private void logForegroundServiceStateChanged(ServiceRecord r, int state, int durationMs) {
		if (!ActivityManagerUtils.shouldSamplePackageForAtom(
		r.packageName, mAm.mConstants.mDefaultFgsAtomSampleRate)) {
		return;
		}
		FrameworkStatsLog.write(FrameworkStatsLog.FOREGROUND_SERVICE_STATE_CHANGED,
		r.appInfo.uid,
		r.shortInstanceName,

services/core/java/com/android/server/am/ActivityManagerConstants.java

+21 −0

Original line number	Diff line number	Diff line
		@@ -97,6 +97,7 @@ final class ActivityManagerConstants extends ContentObserver {
		static final String KEY_BOOT_TIME_TEMP_ALLOWLIST_DURATION = "boot_time_temp_allowlist_duration";
		static final String KEY_FG_TO_BG_FGS_GRACE_DURATION = "fg_to_bg_fgs_grace_duration";
		static final String KEY_FGS_START_FOREGROUND_TIMEOUT = "fgs_start_foreground_timeout";
		static final String KEY_FGS_ATOM_SAMPLE_RATE = "fgs_atom_sample_rate";

		private static final int DEFAULT_MAX_CACHED_PROCESSES = 32;
		private static final long DEFAULT_BACKGROUND_SETTLE_TIME = 60*1000;
		@@ -137,6 +138,7 @@ final class ActivityManagerConstants extends ContentObserver {
		private static final int DEFAULT_BOOT_TIME_TEMP_ALLOWLIST_DURATION = 10 * 1000;
		private static final long DEFAULT_FG_TO_BG_FGS_GRACE_DURATION = 5 * 1000;
		private static final int DEFAULT_FGS_START_FOREGROUND_TIMEOUT_MS = 10 * 1000;
		private static final float DEFAULT_FGS_ATOM_SAMPLE_RATE = 1; // 100 %

		// Flag stored in the DeviceConfig API.
		/**
		@@ -430,6 +432,13 @@ final class ActivityManagerConstants extends ContentObserver {
		*/
		volatile long mFgsStartForegroundTimeoutMs = DEFAULT_FGS_START_FOREGROUND_TIMEOUT_MS;

		/**
		* Sample rate for the FGS westworld atom.
		*
		* If the value is 0.1, 10% of the installed packages would be sampled.
		*/
		volatile float mDefaultFgsAtomSampleRate = DEFAULT_FGS_ATOM_SAMPLE_RATE;

		private final ActivityManagerService mService;
		private ContentResolver mResolver;
		private final KeyValueListParser mParser = new KeyValueListParser(',');
		@@ -629,6 +638,9 @@ final class ActivityManagerConstants extends ContentObserver {
		case KEY_FGS_START_FOREGROUND_TIMEOUT:
		updateFgsStartForegroundTimeout();
		break;
		case KEY_FGS_ATOM_SAMPLE_RATE:
		updateFgsAtomSamplePercent();
		break;
		default:
		break;
		}
		@@ -933,6 +945,13 @@ final class ActivityManagerConstants extends ContentObserver {
		DEFAULT_FGS_START_FOREGROUND_TIMEOUT_MS);
		}

		private void updateFgsAtomSamplePercent() {
		mDefaultFgsAtomSampleRate = DeviceConfig.getFloat(
		DeviceConfig.NAMESPACE_ACTIVITY_MANAGER,
		KEY_FGS_ATOM_SAMPLE_RATE,
		DEFAULT_FGS_ATOM_SAMPLE_RATE);
		}

		private void updateImperceptibleKillExemptions() {
		IMPERCEPTIBLE_KILL_EXEMPT_PACKAGES.clear();
		IMPERCEPTIBLE_KILL_EXEMPT_PACKAGES.addAll(mDefaultImperceptibleKillExemptPackages);
		@@ -1145,6 +1164,8 @@ final class ActivityManagerConstants extends ContentObserver {
		pw.println(mFlagFgsStartRestrictionEnabled);
		pw.print(" "); pw.print(KEY_DEFAULT_FGS_STARTS_RESTRICTION_CHECK_CALLER_TARGET_SDK);
		pw.print("="); pw.println(mFgsStartRestrictionCheckCallerTargetSdk);
		pw.print(" "); pw.print(KEY_FGS_ATOM_SAMPLE_RATE);
		pw.print("="); pw.println(mDefaultFgsAtomSampleRate);

		pw.println();
		if (mOverrideMaxCachedProcesses >= 0) {

services/core/java/com/android/server/am/ActivityManagerUtils.java

0 → 100644

+124 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2021 The Android Open Source Project
		*
		* Licensed under the Apache License, Version 2.0 (the "License");
		* you may not use this file except in compliance with the License.
		* You may obtain a copy of the License at
		*
		* http://www.apache.org/licenses/LICENSE-2.0
		*
		* Unless required by applicable law or agreed to in writing, software
		* distributed under the License is distributed on an "AS IS" BASIS,
		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		* See the License for the specific language governing permissions and
		* limitations under the License.
		*/
		package com.android.server.am;

		import android.app.ActivityThread;
		import android.provider.Settings;
		import android.util.ArrayMap;

		import com.android.internal.annotations.GuardedBy;
		import com.android.internal.annotations.VisibleForTesting;

		import java.security.MessageDigest;
		import java.security.NoSuchAlgorithmException;

		/**
		* To store random utility methods...
		*/
		public class ActivityManagerUtils {
		private ActivityManagerUtils() {
		}

		private static Integer sAndroidIdHash;

		@GuardedBy("sHashCache")
		private static final ArrayMap<String, Integer> sHashCache = new ArrayMap<>();

		private static String sInjectedAndroidId;

		/** Used by the unit tests to inject an android ID. Do not set in the prod code. */
		@VisibleForTesting
		static void injectAndroidIdForTest(String androidId) {
		sInjectedAndroidId = androidId;
		sAndroidIdHash = null;
		}

		/**
		* Return a hash between [0, MAX_VALUE] generated from the android ID.
		*/
		@VisibleForTesting
		static int getAndroidIdHash() {
		// No synchronization is required. Double-initialization is fine here.
		if (sAndroidIdHash == null) {
		final String androidId = Settings.Secure.getString(
		ActivityThread.currentApplication().getContentResolver(),
		Settings.Secure.ANDROID_ID);
		sAndroidIdHash = getUnsignedHashUnCached(
		sInjectedAndroidId != null ? sInjectedAndroidId : androidId);
		}
		return sAndroidIdHash;
		}

		/**
		* Return a hash between [0, MAX_VALUE] generated from a package name, using a cache.
		*
		* Because all the results are cached, do not use it for dynamically generated strings.
		*/
		@VisibleForTesting
		static int getUnsignedHashCached(String s) {
		synchronized (sHashCache) {
		final Integer cached = sHashCache.get(s);
		if (cached != null) {
		return cached;
		}
		final int hash = getUnsignedHashUnCached(s);
		sHashCache.put(s.intern(), hash);
		return hash;
		}
		}

		/**
		* Return a hash between [0, MAX_VALUE] generated from a package name.
		*/
		private static int getUnsignedHashUnCached(String s) {
		try {
		final MessageDigest digest = MessageDigest.getInstance("SHA-1");
		digest.update(s.getBytes());
		return unsignedIntFromBytes(digest.digest());
		} catch (NoSuchAlgorithmException e) {
		throw new RuntimeException(e);
		}
		}

		@VisibleForTesting
		static int unsignedIntFromBytes(byte[] longEnoughBytes) {
		return (extractByte(longEnoughBytes, 0)
		\| extractByte(longEnoughBytes, 1)
		\| extractByte(longEnoughBytes, 2)
		\| extractByte(longEnoughBytes, 3))
		& 0x7FFF_FFFF;
		}

		private static int extractByte(byte[] bytes, int index) {
		return (((int) bytes[index]) & 0xFF) << (index * 8);
		}

		/**
		* @return whether a package should be logged, using a random value based on the ANDROID_ID,
		* with a given sampling rate.
		*/
		public static boolean shouldSamplePackageForAtom(String packageName, float rate) {
		if (rate <= 0) {
		return false;
		}
		if (rate >= 1) {
		return true;
		}
		final int hash = getUnsignedHashCached(packageName) ^ getAndroidIdHash();

		return (((double) hash) / Integer.MAX_VALUE) <= rate;
		}
		}

services/tests/servicestests/src/com/android/server/am/ActivityManagerUtilsTest.java

0 → 100644

+130 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2021 The Android Open Source Project
		*
		* Licensed under the Apache License, Version 2.0 (the "License");
		* you may not use this file except in compliance with the License.
		* You may obtain a copy of the License at
		*
		* http://www.apache.org/licenses/LICENSE-2.0
		*
		* Unless required by applicable law or agreed to in writing, software
		* distributed under the License is distributed on an "AS IS" BASIS,
		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		* See the License for the specific language governing permissions and
		* limitations under the License.
		*/
		package com.android.server.am;

		import static com.google.common.truth.Truth.assertThat;

		import static org.junit.Assert.fail;

		import androidx.test.filters.SmallTest;

		import org.junit.Test;

		@SmallTest
		public class ActivityManagerUtilsTest {
		@Test
		public void getAndroidIdHash() {
		// getAndroidIdHash() essentially returns a random a value. Just make sure it's
		// non-negative.
		assertThat(ActivityManagerUtils.getAndroidIdHash()).isAtLeast(0);
		}

		@Test
		public void getUnsignedHashCached() {
		assertThat(ActivityManagerUtils.getUnsignedHashCached("x")).isEqualTo(
		ActivityManagerUtils.getUnsignedHashCached("x"));

		assertThat(ActivityManagerUtils.getUnsignedHashCached("x")).isNotEqualTo(
		ActivityManagerUtils.getUnsignedHashCached("y"));
		}

		@Test
		public void shouldSamplePackage_sampleNone() {
		final int numTests = 100000;
		for (int i = 0; i < numTests; i++) {
		assertThat(ActivityManagerUtils.shouldSamplePackageForAtom("" + i, 0))
		.isFalse();
		}
		}

		@Test
		public void shouldSamplePackage_sampleAll() {
		final int numTests = 100000;

		for (int i = 0; i < numTests; i++) {
		assertThat(ActivityManagerUtils.shouldSamplePackageForAtom("" + i, 1))
		.isTrue();
		}
		}

		/**
		* Make sure, with the same android ID, an expected rate of the packages are selected.
		*/
		@Test
		public void shouldSamplePackage_sampleSome_fixedAndroidId() {
		checkShouldSamplePackage_fixedAndroidId(0.1f);
		checkShouldSamplePackage_fixedAndroidId(0.5f);
		checkShouldSamplePackage_fixedAndroidId(0.9f);
		}

		/**
		* Make sure, the same package is selected on an expected rate of the devices.
		*/
		@Test
		public void shouldSamplePackage_sampleSome_fixedPackage() {
		checkShouldSamplePackage_fixedPackage(0.1f);
		checkShouldSamplePackage_fixedPackage(0.5f);
		checkShouldSamplePackage_fixedPackage(0.9f);
		}

		private void checkShouldSamplePackage_fixedPackage(float sampleRate) {
		checkShouldSamplePackage(sampleRate, sampleRate, true, false);
		}

		private void checkShouldSamplePackage_fixedAndroidId(float sampleRate) {
		checkShouldSamplePackage(sampleRate, sampleRate, false, true);
		}

		@Test
		public void testSheckShouldSamplePackage() {
		// Just make sure checkShouldSamplePackage is actually working...
		try {
		checkShouldSamplePackage(0.3f, 0.6f, false, true);
		fail();
		} catch (AssertionError expected) {
		}
		try {
		checkShouldSamplePackage(0.6f, 0.3f, true, false);
		fail();
		} catch (AssertionError expected) {
		}
		}

		private void checkShouldSamplePackage(float inputSampleRate, float expectedRate,
		boolean fixedPackage, boolean fixedAndroidId) {
		final int numTests = 100000;

		try {
		int numSampled = 0;
		for (int i = 0; i < numTests; i++) {
		final String pkg = fixedPackage ? "fixed-package" : "" + i;
		ActivityManagerUtils.injectAndroidIdForTest(
		fixedAndroidId ? "fixed-android-id" : "" + i);

		if (ActivityManagerUtils.shouldSamplePackageForAtom(pkg, inputSampleRate)) {
		numSampled++;
		}
		assertThat(ActivityManagerUtils.getUnsignedHashCached(pkg)).isEqualTo(
		ActivityManagerUtils.getUnsignedHashCached(pkg));
		}
		final double actualSampleRate = ((double) numSampled) / numTests;

		assertThat(actualSampleRate).isWithin(0.05).of(expectedRate);
		} finally {
		ActivityManagerUtils.injectAndroidIdForTest(null);
		}
		}
		}