android process information
Android Process Information
本文描述了android启动之后的系统进程列表，并从log的角度来初步分析一下zygote进程的启动过程.
1 Process list:
用PS可以得到进程列表，现就最主要的一些进程作一个简单的介绍：
USER PID PPID VSIZE RSS WCHAN PC NAME
root 1 0 548 196 c00b8c14 0000d5cc S /init
......
root 734 1 72000 14172 c00b92b0 afe0c5a4 S zygote
root 769 1 716 264 c02265ec afe0c1dc S /system/bin/logcat
system 825 734 574128 28360 ffffffff afe0c47c S system_server
radio 877 734 158260 20040 ffffffff afe0d404 S com.android.phone
app_18 960 734 104180 15208 ffffffff afe0d404 S com.android.mms
app_8 979 734 118860 14044 ffffffff afe0d404 S android.process.media
app_9 991 734 91980 12264 ffffffff afe0d404 S com.android.alarmclock
app_14 1025 734 95636 13036 ffffffff afe0d404 S com.android.calendar
app_20 1146 734 99260 15320 ffffffff afe0d404 S com.android.music
app_47 1157 734 100204 15964 ffffffff afe0d404 S com.motorola.camera
app_11 1183 734 122672 23576 ffffffff afe0d404 S com.android.browser
app_6 1199 734 117032 20388 ffffffff afe0d404 S oms.mobilemusic
system 1244 734 99292 15940 ffffffff afe0d404 S com.android.settings
......
正如linux系统一样，第一个启动的进程当然是init了。从以上可以看出，所有应用层的进程都是zygote 的子进程，事实上，jvm的初始化就是从zygote开始的，zygote是init的子进程，zygote是在通过init.rc中启动的。
我们再从以下的启动log 中来理解一下android的启动过程，包括runtime：
2 log:
09-07 06:21:51.218: INFO/vold(538): Android Volume Daemon version 2.0
09-07 06:21:51.227: INFO/DEBUG(539): debuggerd: Jun 30 2009 17:00:51
09-07 06:21:51.247: ERROR/vold(538): Error opening switch name path '/sys/class/switch/test2' (No such file or directory)
09-07 06:21:51.247: ERROR/vold(538): Error bootstrapping switch '/sys/class/switch/test2' (m)
09-07 06:21:51.247: ERROR/vold(538): Error opening switch name path '/sys/class/switch/test' (No such file or directory)
09-07 06:21:51.247: ERROR/vold(538): Error bootstrapping switch '/sys/class/switch/test' (m)
09-07 06:21:51.247: DEBUG/vold(538): Bootstrapping complete
09-07 06:21:51.397: ERROR/flash_image(544): can't find recovery partition
09-07 06:21:51.468: DEBUG/qemud(546): entering main loop
09-07 06:21:52.288: DEBUG/AndroidRuntime(541): >>>>>>>>>>>>>> AndroidRuntime START <<<<<<<<<<<<<<
09-07 06:21:52.288: DEBUG/AndroidRuntime(541): CheckJNI is ON
09-07 06:21:52.407: DEBUG/qemud(546): fdhandler_accept_event: accepting on fd 10
09-07 06:21:52.407: DEBUG/qemud(546): created client 0xe078 listening on fd 8
09-07 06:21:52.407: DEBUG/qemud(546): fdhandler_event: disconnect on fd 8
09-07 06:21:52.458: DEBUG/qemud(546): fdhandler_accept_event: accepting on fd 10
09-07 06:21:52.458: DEBUG/qemud(546): created client 0xf028 listening on fd 8
09-07 06:21:52.458: DEBUG/qemud(546): client_fd_receive: attempting registration for service 'gsm'
09-07 06:21:52.458: DEBUG/qemud(546): client_fd_receive: -> received channel id 1
09-07 06:21:52.468: DEBUG/qemud(546): client_registration: registration succeeded for client 1
09-07 06:21:52.937: INFO/(542): ServiceManager: 0xac38
09-07 06:21:52.957: INFO/AudioFlinger(542): AudioFlinger's thread ready to run for output 0
09-07 06:21:52.957: INFO/CameraService(542): CameraService started: pid=542
09-07 06:21:52.978: DEBUG/AndroidRuntime(541): --- registering native functions ---
09-07 06:21:53.308: INFO/Zygote(541): Preloading classes...
09-07 06:21:53.318: DEBUG/dalvikvm(541): GC freed 764 objects / 42216 bytes in 11ms
09-07 06:21:53.517: DEBUG/dalvikvm(541): GC freed 278 objects / 17160 bytes in 4ms
09-07 06:21:53.898: DEBUG/dalvikvm(541): GC freed 208 objects / 12696 bytes in 6ms
09-07 06:21:53.988: DEBUG/dalvikvm(541): Trying to load lib /system/lib/libmedia_jni.so 0x0
09-07 06:21:54.148: DEBUG/dalvikvm(541): Added shared lib /system/lib/libmedia_jni.so 0x0
09-07 06:21:54.148: DEBUG/dalvikvm(541): Trying to load lib /system/lib/libmedia_jni.so 0x0
09-07 06:21:54.158: DEBUG/dalvikvm(541): Shared lib '/system/lib/libmedia_jni.so' already loaded in same CL 0x0
09-07 06:21:54.158: DEBUG/dalvikvm(541): Trying to load lib /system/lib/libmedia_jni.so 0x0
09-07 06:21:54.158: DEBUG/dalvikvm(541): Shared lib '/system/lib/libmedia_jni.so' already loaded in same CL 0x0
09-07 06:21:54.158: DEBUG/dalvikvm(541): Trying to load lib /system/lib/libmedia_jni.so 0x0
09-07 06:21:54.158: DEBUG/dalvikvm(541): Shared lib '/system/lib/libmedia_jni.so' already loaded in same CL 0x0
09-07 06:21:54.168: DEBUG/dalvikvm(541): GC freed 462 objects / 29144 bytes in 8ms
......
09-07 06:22:03.509: INFO/dalvikvm(541): Splitting out new zygote heap
09-07 06:22:03.569: INFO/dalvikvm(541): System server process 570 has been created
09-07 06:22:03.569: INFO/Zygote(541): Accepting command socket connections
09-07 06:22:03.638: INFO/jdwp(570): received file descriptor 10 from ADB
09-07 06:22:03.797: DEBUG/dalvikvm(570): Trying to load lib /system/lib/libandroid_servers.so 0x0
......
09-07 06:22:04.179: INFO/SystemServer(570): Entered the Android system server!
09-07 06:22:04.209: INFO/sysproc(570): System server: entering thread pool.
09-07 06:22:04.267: ERROR/GLLogger(570): couldn't load <libhgl.so> library (Cannot find library)
09-07 06:22:04.338: INFO/SystemServer(570): Starting Power Manager.
09-07 06:22:04.387: INFO/ARMAssembler(570): generated scanline__00000077:03545404_00000A01_00000000 [ 30 ipp] (51 ins) at [0x190ed0:0x190f9c] in 6840752 ns
09-07 06:22:04.397: INFO/SystemServer(570): Starting Activity Manager.
09-07 06:22:04.578: INFO/SystemServer(570): Starting telephony registry
09-07 06:22:04.588: INFO/SystemServer(570): Starting Package Manager.
09-07 06:22:04.619: INFO/Installer(570): connecting...
09-07 06:22:04.619: INFO/installd(543): new connection
09-07 06:22:04.717: INFO/PackageManager(570): Got library android.awt in /system/framework/android.awt.jar
09-07 06:22:04.728: INFO/PackageManager(570): Got library android.test.runner in /system/framework/android.test.runner.jar
09-07 06:22:04.728: INFO/PackageManager(570): Got library com.android.im.plugin in /system/framework/com.android.im.plugin.jar
09-07 06:22:05.078: DEBUG/PackageManager(570): Scanning app dir /system/framework
......
07 06:22:07.780: INFO/SystemServer(570): Starting Window Manager.
......
07 06:22:22.187: DEBUG/HomeLoaders(611): --> starting applications loader
......
从log 中也可以看出：
1. 在zygote启动之后，GC在不停地进行垃圾回收;
2. Framework中的组件都是在SystemServer初始化的，这一点，从android的源码也能看出来;
3. 最后是启动应用层的组件.