How Applications Are Run on Android ?

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How applications are run on Android ?

Jean-Loup Bogalho & Jérémy Lefaure

Table of contents

1. Dalvik and ART 2. Executable files 3. Memory management 4. Compilation

What is Dalvik ?

● Android’s Virtual Machine ● Designed to run on embedded systems ● Register-based (lower memory consumption) ● Run Dalvik Executable (.dex) files

What is ART ?

● Android RunTime ● Dalvik’s successor ● ART Is Not a JVM ● Huge performance gain thanks to ahead-of-time
(AOT) compilation
● Available in Android 4.4

What is ART ?
Executable files
Dalvik: .dex files

● Not the same bytecode as classical Java bytecode
● .class files are converted in .dex files at build time
● Optimized for minimal memory footprint

Dalvik: .dex files
Dalvik: application installation

● Verification:

○

bytecode check (illegal instructions, valid indices,...) checksum on files

○

● Optimization:

○○○

method inlining byte swapping and padding static linking

ART: OAT file

● Generated during installation (dex2oat) ● ELF format ● Classes metadata

Memory management
Zygote

● Daemon started at boot time ● Loads and initializes core libraries ● Forks to create new Dalvik instance ● Startup time of new VM is reduced ● Memory layouts are shared across processes

Dalvik: memory management

● Memory is garbage collected ● Automatic management avoids programming errors
● Objects are not freed as soon as they become unused

Dalvik: memory allocation

● Allocation profiling:

○ allocation count (succeeded or failed) ○ total allocated size (succeeded or failed)

● malloc function is more complex since memory is garbage collected

Dalvik: memory allocation
Dalvik: memory allocation
Dalvik: memory allocation
Dalvik: memory allocation
Dalvik: memory allocation

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Application Performance Profiling in Android Dalvik Virtual Machines 1297

VOL. E99-D NO. 5 MAY 2016 The usage of this PDF file must comply with the IEICE Provisions on Copyright. The author(s) can distribute this PDF file for research and educational (nonprofit) purposes only. Distribution by anyone other than the author(s) is prohibited. IEICE TRANS. INF. & SYST., VOL.E99–D, NO.5 MAY 2016 1296 PAPER Application Performance Profiling in Android Dalvik Virtual Machines Hung-Cheng CHANG†a), Kuei-Chung CHANG††, Nonmembers, Ying-Dar LIN†, Member, and Yuan-Cheng LAI†††, Nonmember SUMMARY Most Android applications are written in JAVA and run However, some approaches cannot be directly used for on a Dalvik virtual machine. For smartphone vendors and users who wish Android systems. First, the source code of an application to know the performance of an application on a particular smartphone but usually cannot be obtained easily, which makes the source cannot obtain the source code, we propose a new technique, Dalvik Pro- filer for Applications (DPA), to profile an Android application on a Dalvik code instrumentation not feasible. Second, an Android sys- virtual machine without the support of source code. Within a Dalvik vir- tem runs applications on a Dalvik virtual machine (DVM). tual machine, we determine the entry and exit locations of a method, log its A classical Java virtual machine is a stack-based VM, and execution time, and analyze the log to determine the performance of the ap- a Dalvik virtual machine is a register-based VM [12], [13]: plication. Our experimental results show an error ratio of less than 5% from ff ff the baseline tool Traceview which instruments source code.