【Android】CarWatchDog I/O监控服务

Android Car WatchDog I/O监控服务

• 背景：
  某基于Android 13的车载系统。

某天长时间测试一款3方（非SystemApp）时，该款应用偶发闪退现象。
通过日志分析，发现应用被系统的 Car WatchDog（喂狗服务）Disable掉了。
日志如下

Disabled package *** on user*** until used due to resource overuse

对应的代码部分。
/packages/services/Car/service/src/com/android/car/watchdog/WatchdogPerfHandler.java

/** Disables a package for specific user until used. */
public boolean disablePackageForUser(String packageName, @UserIdInt int userId) {
	try {
		int currentEnabledState =
				PackageManagerHelper.getApplicationEnabledSettingForUser(packageName, userId);
		switch (currentEnabledState) {
			case COMPONENT_ENABLED_STATE_DISABLED:
			case COMPONENT_ENABLED_STATE_DISABLED_USER:
			case COMPONENT_ENABLED_STATE_DISABLED_UNTIL_USED:
				Slogf.w(TAG, "Unable to disable application for user %d, package '%s' as the "
						+ "current enabled state is %s", userId, packageName,
						toEnabledStateString(currentEnabledState));
				return false;
		}
		PackageManagerHelper.setApplicationEnabledSettingForUser(packageName,
				COMPONENT_ENABLED_STATE_DISABLED_UNTIL_USED, /* flags= */ 0, userId,
				mContext.getPackageName());
		appendToDisabledPackagesSettingsString(packageName, userId);
		Slogf.i(TAG, "Disabled package '%s' on user %d until used due to resource overuse",
				packageName, userId);
	} catch (Exception e) {
		Slogf.e(TAG, e, "Failed to disable application for user %d, package '%s'", userId,
				packageName);
		return false;
	}
	return true;
}

问题分析

Car WatchDog中的IO Monitor，会监监控所有应用或服务的磁盘I/O用量。以保证系统的稳定。主要包括：

• 应用的磁盘I/O写入量。
• 应用的System-wide I/O写入量（宽带)

当应用或服务超过预定义的阈值时，Car WatchDog会对相应的应用或者服务执行相应操作（比如 kill掉）：

• 系统服务或应用，不受限制（可以通过配置文件指定，哪些系统服务或应用受到监控）
• 三方应用，监控被进行限制。

设定的阈值统计范围时，一天内。
Car WatchDog中的IO Monitor，会统计一天内的I/O使用情况。

上述问题分析

回到上面说的问题。某一款三方应用，偶尔退出，并且系统中存在下述日志。

Disabled package *** on user*** until used due to resource overuse

该日志说明，这款应用因为I/O使用超过阈值，被系统Kill。
后续通过复现，抓取IO相应日志，发现出现问题时该应用，在一天内的写入量超过3GB，这个值已经超过系统的阈值配置。

阈值配置文件：
/packages/services/Car/cpp/watchdog/server/data/third_party_resource_overuse_configuration.xml

<?xml version='1.0' encoding='utf-8'?>
<!-- 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.
-->

<resourceOveruseConfiguration version="1.0">
  <componentType> THIRD_PARTY </componentType>
  <ioOveruseConfiguration>
    <!-- Default thresholds in MiB for all third-party packages that don't have app category
         specific thresholds. -->
    <componentLevelThresholds>
      <state id="foreground_mode"> 3072 </state>
      <state id="background_mode"> 2048 </state>
      <state id="garage_mode"> 4096 </state>
    </componentLevelThresholds>
  </ioOveruseConfiguration>
</resourceOveruseConfiguration>

修改： 去掉该三方引用的无用I/O操作。后续测试，无偶先问题。

关于Android源码部分的实现，可以感兴趣的可以阅读如下源文件。
packages/services/Car/cpp/watchdog/server/src/IoOveruseMonitor.cpp