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中文版本请参看这里

OOMMonitor Introduction

OOMMonitor is designed for solving Android Application's Java memory leak problems，and it's core concepts are:

  • By polling Java heap size, running threads and fd size periodic, Hprof dump is triggered when the threshold is exceeded multiple consecutive times.

  • Hprof dump use Suspend ART VM->fork VM process->Resume ART VM->Dump Hprof strategy, making the simple dump's 20 seconds process frozen reduced to within 20ms.

  • Using shark to parse hprof file, but some optimization changes are added in shark. Leaking judge and leaking reference chain computing are executed on the device, and give a heap report finally.

OOMMonitor Compatibility

  • Android L and above（API level >= 21）

  • Support armeabi-v7a arm64-v8a x86 x86-64

OOMMonitor Quick up

dependencies

  • Add mavenCentral to the repositories of the project root directory build.gradle
repositories {
    mavenCentral()
}
  • Add dependency in project app/build.gradle
dependencies {
    implementation "com.kuaishou.koom:koom-java-leak:${latest_version}"
}

Steps

  • MonitorManager Initialization

Make sure MonitorManager is initialized for OOMMonitor depends on it, such as Application, App version code is correctly initialized.

  • OOMMonitor Initialization
val config = OOMMonitorConfig.Builder()
    .setThreadThreshold(50) //50 only for test! Please use default value!
    .setFdThreshold(300) // 300 only for test! Please use default value!
    .setHeapThreshold(0.9f) // 0.9f for test! Please use default value!
    .setVssSizeThreshold(1_000_000) // 1_000_000 for test! Please use default value!
    .setMaxOverThresholdCount(1) // 1 for test! Please use default value!
    .setAnalysisMaxTimesPerVersion(3) // Consider use default value！
    .setAnalysisPeriodPerVersion(15 * 24 * 60 * 60 * 1000) // Consider use default value！
    .setLoopInterval(5_000) // 5_000 for test! Please use default value!
    .setEnableHprofDumpAnalysis(true)
    .setHprofUploader(object: OOMHprofUploader {
      override fun upload(file: File, type: OOMHprofUploader.HprofType) {
        MonitorLog.e("OOMMonitor", "todo, upload hprof ${file.name} if necessary")
      }
    })
    .setReportUploader(object: OOMReportUploader {
      override fun upload(file: File, content: String) {
        MonitorLog.i("OOMMonitor", content)
        MonitorLog.e("OOMMonitor", "todo, upload report ${file.name} if necessary")
      }
    })
    .build()

MonitorManager.addMonitorConfig(config)
  • Start OOMMonitor
OOMMonitor.startLoop(5_000L)
  • Stop OOMMonitor
OOMMonitor.stopLoop()
  • Check Running Log
    • start loop，OOMMonitor: startLoop()
    • exceed the threshold，OOMMonitor_ThreadOOMTracker: [meet condition] overThresholdCount:1, threadCount: 717
    • dump triggered，OOMMonitor: dumpAndAnalysis
    • dump ended：OOMMonitor: end hprof dump
    • start hprof analyze：OOMMonitor: start hprof analysis
    • hprof analysis ended ：OOMMonitor: heap analysis success, do upload

OOMMonitor FAQ

  • How about OOMMonitor performance overhead？

    • First, dump hprof will no longer froze the process
    • But, dump and analysis in the sub process may compute above 3 minutes which up to heap file size, and this will use one cpu thread and 200m memory maximum
    • So，a remote switch and a sample rate is suggested

  • What object is considered leaked？

    • For Activity and Fragment, when object is destroyed but a reference chain to gc root still exist, the object is leaked
      • Activity destroy judgement rule，mFinished or mDestroyed is true
      • Fragment destroy judgement rule，mFragmentManager is null and mCalled is true, mCalled is true means the fragment lifecycle callback is done

  • How to strip hprof in the dump process to reduced the hprof file size mostly？

    • strip dump in the subprocess

      ForkStripHeapDumper.getInstance().dump(path)

  • How to refill the stripped hprof， make it available to AS Profiler and MAT？

    • fetch the hprof from the device

      adb shell "run-as com.kwai.koom.demo cat 'files/test.hprof'" > ~/temp/test.hprof

    • Usetools/koom-fill-crop.jar to refill the stripped hprof

      java -jar koom-fill-crop.jar test.hprof

  • How to read the report file？

    • Please read the comments in the HeapReport.java

  • How to de-obfuscate the report？

    • Use proguard ReTrace