Android Dalvik VM - Revision history

Tim Bird: /* Debugging the VM */ add information about checkJNI and stack trace dump via SIGQUIT

2011-09-15T18:18:04Z

‎Debugging the VM: add information about checkJNI and stack trace dump via SIGQUIT

Tim Bird: /* Debugging the VM */

2011-09-15T18:00:10Z

‎Debugging the VM

Tim Bird at 17:54, 15 September 2011

2011-09-15T17:54:51Z

Wmat: Added page to Category:Android

2011-02-22T20:07:47Z

Added page to Category:Android

Tim Bird: add link to Myriad Alien Dalvik information

2011-02-10T17:52:39Z

add link to Myriad Alien Dalvik information

Tim Bird: add link to docs and some miscellaneous info about dalvik

2011-01-11T18:50:08Z

add link to docs and some miscellaneous info about dalvik

Tim Bird: /* JIT */ fix typo

2011-01-11T18:11:17Z

‎JIT: fix typo

Tim Bird: add stuff about relationship to java and expand JIT section

2010-07-15T20:33:22Z

add stuff about relationship to java and expand JIT section

Tim Bird: add jit info, and fix some links

2010-07-15T20:13:27Z

add jit info, and fix some links

Tim Bird at 20:03, 15 July 2010

2010-07-15T20:03:54Z

@@ Line 75: / Line 75: @@
 using 'kill -3 <pid>', where pid in the main dalvik process.  By default, the stack trace goes to the android log,
 but you can have the data sent to a file (using the dalvik.vm.stack-trace-file property) instead.
 == Resources ==

← Older revision		Revision as of 18:00, 15 September 2011
Line 60:		Line 60:

	See http://netmite.com/android/mydroid/dalvik/docs/embedded-vm-control.html		See http://netmite.com/android/mydroid/dalvik/docs/embedded-vm-control.html
		+
		+	(Note that this is in <aosp-root>/dalvik/docs, along with a whole bunch of other files
		+	with information about Dalvik.)

	this mentions a number of features you can control with properties, including:		this mentions a number of features you can control with properties, including:

@@ Line 54: / Line 54: @@
 * Myriad Alien Dalvik - an implementation of the Dalvik VM for other platforms (demonstrated first on Meego)
 ** http://www.linuxfordevices.com/c/a/News/Myriad-Group-Myriad-Alien-Dalvik/?kc=LNXDEVNL020911
 == Resources ==

← Older revision		Revision as of 20:07, 22 February 2011
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	* [http://developer.android.com/reference/dalvik/bytecode/Opcodes.html Dalvik bytecodes]		* [http://developer.android.com/reference/dalvik/bytecode/Opcodes.html Dalvik bytecodes]
		+
		+	[[Category:Android]]

← Older revision		Revision as of 17:52, 10 February 2011
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	As of March 2010, only the Sun JDK, version 1.5 is supported for building the Android system and add-on Android applications.		As of March 2010, only the Sun JDK, version 1.5 is supported for building the Android system and add-on Android applications.
		+
		+	== Dalvik on other platforms ==
		+	* Myriad Alien Dalvik - an implementation of the Dalvik VM for other platforms (demonstrated first on Meego)
		+	** http://www.linuxfordevices.com/c/a/News/Myriad-Group-Myriad-Alien-Dalvik/?kc=LNXDEVNL020911

	== Resources ==		== Resources ==

← Older revision		Revision as of 18:50, 11 January 2011
Line 8:		Line 8:

	Most Android applications are delivered and stored on the system as packages (.apks), which include both dex bytes code (classes and methods) and resources. During first boot-up the system creates a cache of dex classes in /data/dalvik-cache.		Most Android applications are delivered and stored on the system as packages (.apks), which include both dex bytes code (classes and methods) and resources. During first boot-up the system creates a cache of dex classes in /data/dalvik-cache.
		+
		+	== Documentation ==
		+	There is some documentation on Dalvik in the source code in the dalvik/docs directory.
		+	See the [http://android.git.kernel.org/?p=platform/dalvik.git;a=tree;f=docs; Android dalvik docs git repository].
		+
		+	The source code has some rather large comments, including near the top of
		+	Thread.c and Exception.c. The "mterp" directory has some notes describing the structure of the
		+	interpreters.
		+
		+	== Q&A ==
		+	From fadden on the android-platform list:
		+
		+	* Who is responsible to read the dex file and call Dalvik ?
		+	**The VM is started by the framework, through the JNI invocation interface. See AndroidRuntime.cpp in frameworks/base/...
		+
		+	* Do you have a tutorial launch an app in the terminal adb: bytecode file > dex file > app launch in Dalvik => and see the result in adb ?
		+	** See "hello-world.html" in the dalvik/docs directory (linked above).
		+
		+	* Is there a profiler inside Dalvik, which enable us to follow each step in the dalvik execution ?
		+	** You could turn on LOG_INSTR to see each instruction as it is executed. This results in a rather dramatic amount of logging. If you try to do this on a device you will overrun the 64KB kernel log buffer pretty quickly and drop lots of stuff, so it's really only suitable for a "desktop" build (e.g. sim-eng).
		+	** Also, Dalvik does include instrumentation to allow for tracing and profiling. See http://elinux.org/Android_Tools#traceview
		+

	== JIT ==		== JIT ==

@@ Line 15: / Line 15: @@
 ** [http://dl.google.com/googleio/2010/android-jit-compiler-androids-dalvik-vm.pdf Slides, in PDF]
-The Dalvik JIT, as of version 2.2, is a "trace-granularity JIT", which means that it compiles individual code fragments that it discovers at runtime to be "hot spots".  (That it, it does not
+The Dalvik JIT, as of version 2.2, is a "trace-granularity JIT", which means that it compiles individual code fragments that it discovers at runtime to be "hot spots".  (That is, it does not
 compile whole methods.)  The Dalvik bytecode interpreter is constantly profiling the code it is executing, and when a piece of code is determined to be running a lot, it is passed to a compiler to turn into native code.  Several optimizations may be performed in this process.  This code is then executed instead of the bytecode, for future runs through this section of the software.

@@ Line 7: / Line 7: @@
 Dalvik was written so that a device can run multiple VMs efficiently. The Dalvik VM executes code in the Dalvik Executable (.dex) format which is optimized for minimal memory footprint. The VM is register-based, and runs classes compiled by a Java language compiler that have been transformed into the .dex format by the included "dx" tool.
-Most Android applications are delivered and stored on the system as packages (.apks), which include both dex bytes code (classes and methods) and resources.  During first boot-up (and subsequently during application install?) the system creates a cache of
+Most Android applications are delivered and stored on the system as packages (.apks), which include both dex bytes code (classes and methods) and resources.  During first boot-up the system creates a cache of dex classes in /data/dalvik-cache.
 == JIT ==
-As of version 2.2 (''Froyo''), Dalvik includes a JIT.
+As of version 2.2 (''Froyo''), Dalvik includes a Just-In-Time compiler (or JIT).
 * See [http://code.google.com/events/io/2010/sessions/jit-compiler-androids-dalvik-vm.html A JIT Compiler for Android's Dalvik VM] - video of presentation by Ben Cheng and Bill Buzbee at Google IO, 2010
 == Resources ==

@@ Line 7: / Line 7: @@
 Dalvik was written so that a device can run multiple VMs efficiently. The Dalvik VM executes code in the Dalvik Executable (.dex) format which is optimized for minimal memory footprint. The VM is register-based, and runs classes compiled by a Java language compiler that have been transformed into the .dex format by the included "dx" tool.
-Most Android applications are presented to the system as packages, which include both dex bytes code (classes and methods) and resources.
+Most Android applications are delivered and stored on the system as packages (.apks), which include both dex bytes code (classes and methods) and resources.  During first boot-up (and subsequently during application install?) the system creates a cache of
 == Resources ==
 * [http://en.wikipedia.org/wiki/Dalvik_(software) Dalvik wikipedia entry]
-* [http://sites.google.com/site/io/dalvik-vm-internals Presentation from Google I/O 2008 on Dalvik VM] by Dan Bornstein
+* [http://sites.google.com/site/io/dalvik-vm-internals Dalvik VM Internals] - video of presentation by Dan Bornstein at Google IO, 2008
 * [http://www.retrodev.com/android/dexformat.html DEX file format], reverse engineered by Michael Pavone
 * [http://developer.android.com/reference/dalvik/bytecode/Opcodes.html Dalvik bytecodes]

@@ Line 3: / Line 3: @@
 Every Android application runs in its own process, with its own instance of the Dalvik virtual machine.
-At boot time, a single virtual machine, called 'zygote' is created, which preloads a long list of classes. (As of Android version 2.1 (eclair), the list of classes preloaded by zygote had 1,942 entries).  All other "java" programs or services are forked from this process, and run in their own process space.
+At boot time, a single virtual machine, called 'zygote' is created, which preloads a long list of classes. (As of Android version 2.1 (eclair), the list of classes preloaded by zygote had 1,942 entries).  All other "java" programs or services are forked from this process, and run as their own process (and threads) in their own address space.  Both applications and system services in the Android framework are implemented in "java".
 Dalvik was written so that a device can run multiple VMs efficiently. The Dalvik VM executes code in the Dalvik Executable (.dex) format which is optimized for minimal memory footprint. The VM is register-based, and runs classes compiled by a Java language compiler that have been transformed into the .dex format by the included "dx" tool.