Android Zygote Startup - Revision history

Wmat: Added page to Category:Android

2011-02-22T20:14:09Z

Added page to Category:Android

Keesj at 20:20, 23 January 2011

2011-01-23T20:20:51Z

Tim Bird: /* Sequence of startup steps */

2010-09-02T19:33:36Z

‎Sequence of startup steps

Tim Bird: /* Sequence of startup steps */

2010-09-02T19:17:49Z

‎Sequence of startup steps

Tim Bird: /* Sequence of startup steps */ add system server startup steps

2010-09-02T19:17:10Z

‎Sequence of startup steps: add system server startup steps

Tim Bird: add bootup sequence notes

2010-09-02T19:09:56Z

add bootup sequence notes

New page

Here are some miscellaneous notes on Android startup of the zygote process.

This information is true for eclair, as of August 2010.
== Sequence of startup steps ==

* init runs the C++ program /system/bin/app_process, and gives the resulting process the name "zygote"
** This is based on the line from init.rc:
service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server
* app_process executes, and executes a runtime environment for a dalvik class
** app_process usage claims to be:
Usage: app_process [java-options] cmd-dir start-class-name [options]
** but you can specify --zygote in place of the start-class-name.
** In the bootup case, --zygote is used
** source for 'app_process is in frameworks/base/cmds/app_process/app_main.cpp
** this is the program to debug when debugging zygote/dalvik itself
* app_process does a 'runtime.start("com.android.internal.os.ZygoteInit", startSystemServer)
** the startSystemServer flag is passed as a parameter on to app_process, to indicate whether to start the system server (duh)
* runtime is an instance of class AppRuntime, which is sub-classed from AndroidRuntime
* AndroidRuntime is the main class for starting the dalvik runtime environment
** source is in frameworks/base/core/jni/AndroidRuntime.cpp
** the start() method starts the virtual machine
*** LOG_BOOT_PROGRESS_START is emitted, with systemTime(SYSTEM_TIME_MONOTONIC)
*** startVM() is called
*** eventually, callStaticVoidMethod() is called, to actually start executing the start class with method "main" in Dalvik code
* com.android.internal.os.ZygoteInit:main() starts executing
** source is at: frameworks/base/core/java/com/android/internal/os/ZygoteInit.java
* the profiler is started
* the Zygote socket is registered (for later communication to start apps)
* classes and resources are preloaded
* zygote runs in "select loop mode", where a single process spins waiting for communication to start subsequent apps
** see runSelectLoopMode()
*** new connections are accepted (and put into array "peers")
*** the spawn command received over the network is executed by calling the runOnce() method
*** source code for this is at: frameworks/base/core/java/com/android/internal/os/ZygoteConnection.java
* eventually, a call is made to Zygote.forkAndSpecialize(), which does the actual forking

← Older revision		Revision as of 20:14, 22 February 2011
Line 84:		Line 84:
	** Backup Service		** Backup Service
	** AppWidget Service		** AppWidget Service
		+
		+	[[Category:Android]]

@@ Line 81: / Line 81: @@
 ** Audio Service
 ** Headset Observer
-** Doc Observer
+** Dock Observer
 ** Backup Service
 ** AppWidget Service

@@ Line 31: / Line 31: @@
 ** the command line to the system server is:
   --setuid=1000 --setgid=1000 \
-  --setgroups=1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,3001,3002,3003
+  --setgroups=1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,3001,3002,3003 \
   --capabilities=130104352,130104352 \
-  --runtime-init
+  --runtime-init \
-  --nice-name=system_server
+  --nice-name=system_server \
 ** the class which starts executing is: com.android.server.SystemServer
 ** a call is made to Zygote.forkSystemServer() to actually start this other process

@@ Line 2: / Line 2: @@
 This information is true for eclair, as of August 2010.
-== Sequence of startup steps ==
+== Sequence of Zygote startup steps ==
 * init runs the C++ program /system/bin/app_process, and gives the resulting process the name "zygote"
@@ Line 44: / Line 44: @@
 *** source code for this is at: frameworks/base/core/java/com/android/internal/os/ZygoteConnection.java
 * eventually, a call is made to Zygote.forkAndSpecialize(), which does the actual forking

@@ Line 28: / Line 28: @@
 * the Zygote socket is registered (for later communication to start apps)
 * classes and resources are preloaded
 * zygote runs in "select loop mode", where a single process spins waiting for communication to start subsequent apps
 ** see runSelectLoopMode()