Android log常用分析方法

logcat

event log

這種log framework層常常使用，通過類似EventLog.writeEvent()寫log，這種log被保存在/system/etc/event-log-tags，如果要看這種log，通過類似logcat -b events -v threadtime這種方式打印出來，輸出的格式類似於下面：

02-18 12:29:22.625   451   467 I am_create_task: [0,116]
02-18 12:29:22.625   451   467 I am_create_activity: [0,114895309,116,com.xd.ro.roapk/com.xindong.RODevelop.UnitySavePicActivity,android.intent.action.MAIN,NULL,NULL,270532608]
02-18 12:29:22.626   451   467 I wm_task_created: [116,1]
02-18 12:29:22.626   451   467 I wm_task_moved: [116,1,0]

它的格式就是

timestamp PID TID log-level log-tag tag-values

每個log-tag都能在framework下的源代碼中找到，如上面的am_create_task，它的tag是在frameworks/base/services/core/java/com/android/server/am/EventLogTags.logtags定義的。某種程度上說，要檢查event log，必須去找這些EventLogTags.logtags，才能清楚知道是啥意思。

ANR

應用在一定時間內由於主線程阻塞而沒做出相應，系統將會殺死這個進程並且dump棧信息到/data/anr目錄中。

檢查ANR log需要兩種類型的log，需要event log/logcat和/data/anr下的log。
event log的意思就是上節說的event log，logcat就是我們常常用logcat後面不加-b打印出來的log，這兩種log主要是爲了找出發生ANR的進程號和發生ARN時的類信息，沒有現成的例子，拿網上的例子做個說明。

如果是event log，搜索“am_anr”關鍵字：

10-01 18:12:49.599  4600  4614 I am_anr  : [0,29761,com.google.android.youtube,953695941,executing service com.google.android.youtube/com.google.android.apps.youtube.app.offline.transfer.OfflineTransferService]
10-01 18:14:10.211  4600  4614 I am_anr  : [0,30363,com.google.android.apps.plus,953728580,executing service com.google.android.apps.plus/com.google.android.apps.photos.service.PhotosService]

如果是logcat log，搜索關鍵字“ANR”:

10-01 18:13:11.984  4600  4614 E ActivityManager: ANR in com.google.android.youtube
10-01 18:14:31.720  4600  4614 E ActivityManager: ANR in com.google.android.apps.plus
10-01 18:14:31.720  4600  4614 E ActivityManager: PID: 30363
10-01 18:14:31.720  4600  4614 E ActivityManager: Reason: executing service com.google.android.apps.plus/com.google.android.apps.photos.service.PhotosService
10-01 18:14:31.720  4600  4614 E ActivityManager: Load: 35.27 / 23.9 / 16.18
10-01 18:14:31.720  4600  4614 E ActivityManager: CPU usage from 16ms to 21868ms later:
10-01 18:14:31.720  4600  4614 E ActivityManager:   74% 3361/mm-qcamera-daemon: 62% user + 12% kernel / faults: 15276 minor 10 major
10-01 18:14:31.720  4600  4614 E ActivityManager:   41% 4600/system_server: 18% user + 23% kernel / faults: 18597 minor 309 major
10-01 18:14:31.720  4600  4614 E ActivityManager:   32% 27420/com.google.android.GoogleCamera: 24% user + 7.8% kernel / faults: 48374 minor 338 major
10-01 18:14:31.720  4600  4614 E ActivityManager:   16% 130/kswapd0: 0% user + 16% kernel
10-01 18:14:31.720  4600  4614 E ActivityManager:   15% 283/mmcqd/0: 0% user + 15% kernel
...
10-01 18:14:31.720  4600  4614 E ActivityManager:   0.1% 27248/irq/503-synapti: 0%
10-01 18:14:31.721  4600  4614 I ActivityManager: Killing 30363:com.google.android.apps.plus/u0a206 (adj 0): bg anr

通過這兩種log都能看出進程30363在執行com.google.android.apps.plus/com.google.android.apps.photos.service.PhotosService時發生了ANR，event log更加簡明，不過需要對着EventLogTags.logtags文件看，logcat更加易懂寫。看自己的喜好吧。

接着需要看/data/anr下traces.txt文件的棧信息了，看棧信息的主要注意事項就是要確保該traces.txt是對應ANR的文件，因爲系統可能發生了多次ARN，/data/anr路徑下可能有多個文件，接着我們要找到發生ANR進程的棧信息：

----- pid 30363 at 2015-10-01 18:14:11 -----
Cmd line: com.google.android.apps.plus
Build fingerprint: 'google/angler/angler:6.0/MDA89D/2294819:userdebug/dev-keys'
ABI: 'arm'
Build type: optimized
Zygote loaded classes=3978 post zygote classes=27
Intern table: 45068 strong; 21 weak
JNI: CheckJNI is off; globals=283 (plus 360 weak)
Libraries: /system/lib/libandroid.so /system/lib/libcompiler_rt.so /system/lib/libjavacrypto.so /system/lib/libjnigraphics.so /system/lib/libmedia_jni.so /system/lib/libwebviewchromium_loader.so libjavacore.so (7)
Heap: 29% free, 21MB/30MB; 32251 objects
Dumping cumulative Gc timings
Total number of allocations 32251
Total bytes allocated 21MB
Total bytes freed 0B
Free memory 9MB
Free memory until GC 9MB
Free memory until OOME 490MB
Total memory 30MB
Max memory 512MB
Zygote space size 1260KB
Total mutator paused time: 0
Total time waiting for GC to complete: 0
Total GC count: 0
Total GC time: 0
Total blocking GC count: 0
Total blocking GC time: 0

suspend all histogram:  Sum: 119.728ms 99% C.I. 0.010ms-107.765ms Avg: 5.442ms Max: 119.562ms
DALVIK THREADS (12):
"Signal Catcher" daemon prio=5 tid=2 Runnable
  | group="system" sCount=0 dsCount=0 obj=0x12c400a0 self=0xef460000
  | sysTid=30368 nice=0 cgrp=default sched=0/0 handle=0xf4a69930
  | state=R schedstat=( 9021773 5500523 26 ) utm=0 stm=0 core=1 HZ=100
  | stack=0xf496d000-0xf496f000 stackSize=1014KB
  | held mutexes= "mutator lock"(shared held)
  native: #00 pc 0035a217  /system/lib/libart.so (art::DumpNativeStack(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, int, char const*, art::ArtMethod*, void*)+126)
  native: #01 pc 0033b03b  /system/lib/libart.so (art::Thread::Dump(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) const+138)
  native: #02 pc 00344701  /system/lib/libart.so (art::DumpCheckpoint::Run(art::Thread*)+424)
  native: #03 pc 00345265  /system/lib/libart.so (art::ThreadList::RunCheckpoint(art::Closure*)+200)
  native: #04 pc 00345769  /system/lib/libart.so (art::ThreadList::Dump(std::__1::basic_ostream<char, std::__1::char_traits<char> >&)+124)
  native: #05 pc 00345e51  /system/lib/libart.so (art::ThreadList::DumpForSigQuit(std::__1::basic_ostream<char, std::__1::char_traits<char> >&)+312)
  native: #06 pc 0031f829  /system/lib/libart.so (art::Runtime::DumpForSigQuit(std::__1::basic_ostream<char, std::__1::char_traits<char> >&)+68)
  native: #07 pc 00326831  /system/lib/libart.so (art::SignalCatcher::HandleSigQuit()+896)
  native: #08 pc 003270a1  /system/lib/libart.so (art::SignalCatcher::Run(void*)+324)
  native: #09 pc 0003f813  /system/lib/libc.so (__pthread_start(void*)+30)
  native: #10 pc 00019f75  /system/lib/libc.so (__start_thread+6)
  (no managed stack frames)

"main" prio=5 tid=1 Suspended
  | group="main" sCount=1 dsCount=0 obj=0x747552a0 self=0xf5376500
  | sysTid=30363 nice=0 cgrp=default sched=0/0 handle=0xf74feb34
  | state=S schedstat=( 331107086 164153349 851 ) utm=6 stm=27 core=3 HZ=100
  | stack=0xff00f000-0xff011000 stackSize=8MB
  | held mutexes=
  kernel: __switch_to+0x7c/0x88
  kernel: futex_wait_queue_me+0xd4/0x130
  kernel: futex_wait+0xf0/0x1f4
  kernel: do_futex+0xcc/0x8f4
  kernel: compat_SyS_futex+0xd0/0x14c
  kernel: cpu_switch_to+0x48/0x4c
  native: #00 pc 000175e8  /system/lib/libc.so (syscall+28)
  native: #01 pc 000f5ced  /system/lib/libart.so (art::ConditionVariable::Wait(art::Thread*)+80)
  native: #02 pc 00335353  /system/lib/libart.so (art::Thread::FullSuspendCheck()+838)
  native: #03 pc 0011d3a7  /system/lib/libart.so (art::ClassLinker::LoadClassMembers(art::Thread*, art::DexFile const&, unsigned char const*, art::Handle<art::mirror::Class>, art::OatFile::OatClass const*)+746)
  native: #04 pc 0011d81d  /system/lib/libart.so (art::ClassLinker::LoadClass(art::Thread*, art::DexFile const&, art::DexFile::ClassDef const&, art::Handle<art::mirror::Class>)+88)
  native: #05 pc 00132059  /system/lib/libart.so (art::ClassLinker::DefineClass(art::Thread*, char const*, unsigned int, art::Handle<art::mirror::ClassLoader>, art::DexFile const&, art::DexFile::ClassDef const&)+320)
  native: #06 pc 001326c1  /system/lib/libart.so (art::ClassLinker::FindClassInPathClassLoader(art::ScopedObjectAccessAlreadyRunnable&, art::Thread*, char const*, unsigned int, art::Handle<art::mirror::ClassLoader>, art::mirror::Class**)+688)
  native: #07 pc 002cb1a1  /system/lib/libart.so (art::VMClassLoader_findLoadedClass(_JNIEnv*, _jclass*, _jobject*, _jstring*)+264)
  native: #08 pc 002847fd  /data/dalvik-cache/arm/system@[e-mail] (Java_java_lang_VMClassLoader_findLoadedClass__Ljava_lang_ClassLoader_2Ljava_lang_String_2+112)
  at java.lang.VMClassLoader.findLoadedClass!(Native method)
  at java.lang.ClassLoader.findLoadedClass(ClassLoader.java:362)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:499)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
  at android.app.ActivityThread.installProvider(ActivityThread.java:5141)
  at android.app.ActivityThread.installContentProviders(ActivityThread.java:4748)
  at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4688)
  at android.app.ActivityThread.-wrap1(ActivityThread.java:-1)
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1405)
  at android.os.Handler.dispatchMessage(Handler.java:102)
  at android.os.Looper.loop(Looper.java:148)
  at android.app.ActivityThread.main(ActivityThread.java:5417)
  at java.lang.reflect.Method.invoke!(Native method)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

  ...
  Stacks for other threads in this process follow
  ...

死鎖

對於普通應用，死鎖常常會以ANR的形式出現，但如果是對於system server進程，看門狗會要死system server進程，從而導致系統重啓，而且這種情況會有類似“WATCHDOG KILLING SYSTEM PROCESS”這種log出現。

檢查這種問題，需要檢查VM的log，這是logcat就不行了，抓dumpstate的log吧，然後搜索“held by thread”關鍵字，然後一點一點細緻的檢查，如下面網上的log：

"Binder_B" prio=5 tid=73 Blocked
  | group="main" sCount=1 dsCount=0 obj=0x13faa0a0 self=0x95e24800
  | sysTid=2016 nice=0 cgrp=default sched=0/0 handle=0x8b68d930
  | state=S schedstat=( 9351576559 4141431119 16920 ) utm=819 stm=116 core=1 HZ=100
  | stack=0x8b591000-0x8b593000 stackSize=1014KB
  | held mutexes=
  at com.android.server.pm.UserManagerService.exists(UserManagerService.java:387)
  - waiting to lock <0x025f9b02> (a android.util.ArrayMap) **held by thread 20**
  at com.android.server.pm.PackageManagerService.getApplicationInfo(PackageManagerService.java:2848)
  at com.android.server.AppOpsService.getOpsRawLocked(AppOpsService.java:881)
  at com.android.server.AppOpsService.getOpsLocked(AppOpsService.java:856)
  at com.android.server.AppOpsService.noteOperationUnchecked(AppOpsService.java:719)
  - locked <0x0231885a> (a com.android.server.AppOpsService)
  at com.android.server.AppOpsService.noteOperation(AppOpsService.java:713)
  at com.android.server.AppOpsService$2.getMountMode(AppOpsService.java:260)
  at com.android.server.MountService$MountServiceInternalImpl.getExternalStorageMountMode(MountService.java:3416)
  at com.android.server.am.ActivityManagerService.startProcessLocked(ActivityManagerService.java:3228)
  at com.android.server.am.ActivityManagerService.startProcessLocked(ActivityManagerService.java:3170)
  at com.android.server.am.ActivityManagerService.startProcessLocked(ActivityManagerService.java:3059)
  at com.android.server.am.BroadcastQueue.processNextBroadcast(BroadcastQueue.java:1070)
  - locked <0x044d166f> (a com.android.server.am.ActivityManagerService)
  at com.android.server.am.ActivityManagerService.finishReceiver(ActivityManagerService.java:16950)
  at android.app.ActivityManagerNative.onTransact(ActivityManagerNative.java:494)
  at com.android.server.am.ActivityManagerService.onTransact(ActivityManagerService.java:2432)
  at android.os.Binder.execTransact(Binder.java:453)
...
  "PackageManager" prio=5 tid=20 Blocked
  | group="main" sCount=1 dsCount=0 obj=0x1304f4a0 self=0xa7f43900
  | sysTid=1300 nice=10 cgrp=bg_non_interactive sched=0/0 handle=0x9fcf9930
  | state=S schedstat=( 26190141996 13612154802 44357 ) utm=2410 stm=209 core=2 HZ=100
  | stack=0x9fbf7000-0x9fbf9000 stackSize=1038KB
  | held mutexes=
  at com.android.server.AppOpsService.noteOperationUnchecked(AppOpsService.java:718)
  - waiting to lock <0x0231885a> (a com.android.server.AppOpsService) **held by thread 73**
  at com.android.server.AppOpsService.noteOperation(AppOpsService.java:713)
  at com.android.server.AppOpsService$2.getMountMode(AppOpsService.java:260)
  at com.android.server.AppOpsService$2.hasExternalStorage(AppOpsService.java:273)
  at com.android.server.MountService$MountServiceInternalImpl.hasExternalStorage(MountService.java:3431)
  at com.android.server.MountService.getVolumeList(MountService.java:2609)
  at android.os.storage.StorageManager.getVolumeList(StorageManager.java:880)
  at android.os.Environment$UserEnvironment.getExternalDirs(Environment.java:83)
  at android.os.Environment.isExternalStorageEmulated(Environment.java:708)
  at com.android.server.pm.PackageManagerService.isExternalMediaAvailable(PackageManagerService.java:9327)
  at com.android.server.pm.PackageManagerService.startCleaningPackages(PackageManagerService.java:9367)
  - locked <0x025f9b02> (a android.util.ArrayMap)
  at com.android.server.pm.PackageManagerService$PackageHandler.doHandleMessage(PackageManagerService.java:1320)
  at com.android.server.pm.PackageManagerService$PackageHandler.handleMessage(PackageManagerService.java:1122)
  at android.os.Handler.dispatchMessage(Handler.java:102)
  at android.os.Looper.loop(Looper.java:148)
  at android.os.HandlerThread.run(HandlerThread.java:61)
  at com.android.server.ServiceThread.run(ServiceThread.java:46)

線程73要的鎖被線程20持有，而線程20申請的鎖被線程73持有。

Activities

看焦點activity

關鍵字am_focused_activity

進程啓動歷史

關鍵字Start proc

確認設備是否抖動

關鍵字am_proc_died和am_proc_start，檢查是否在短時間內出現了大量的這樣的log