Dan Bornstein. Google. Dalvik VM Internals It is a virtual machine to What is the Dalvik VM? • run on a slow CPU. • with relatively little RAM. • on an OS. While Google has selected Java as the language for developing Android This paper looks to understand the architecture of Dalvik virtual machine and. Dalvík and the Android Architecture. The Dalvík Virtual Machine* is: ▫ Customized , optimized JVM. – Based on Apache “Harmony” JVM. ▫ Java compiles into DEX.

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Android runtime Nadroid is the managed runtime used by applications and some system services on Android. ART and its predecessor Dalvik were originally created specifically for the Android project.

Dalvik VM Internals – Google I/O Session Videos and Slides

However, some techniques that work on Dalvik do not work on ART. ART also has tighter install-time verification than Dalvik. At install time, ART compiles apps using the on-device dex2oat lnternals. This utility accepts DEX files as input and generates a compiled app executable for the target device.

ART and Dalvik

The utility should be able to compile all valid DEX files without difficulty. However, some post-processing tools produce invalid androie that may be tolerated by Dalvik but cannot be compiled by ART. For more information, see Addressing Garbage Collection Issues. Garbage collection GC can impair an app’s performance, resulting in choppy display, poor UI responsiveness, and other problems. ART improves garbage collection in several ways:. Historically, developers have used the Traceview tool designed for tracing application execution as a profiler.

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While Traceview gives useful information, its results on Dalvik have been skewed by the per-method-call overhead, and use of the tool noticeably affects run time performance.

ART adds support for a dedicated sampling profiler that does not have these limitations. This gives a more accurate view of app execution without significant slowdown.

Sampling support was added to Traceview for Dalvik in the KitKat release. ART supports a number of new debugging options, particularly in monitor- and garbage collection-related functionality. For example, androd can:.

ART gives you as much context and detail as possible when runtime exceptions occur. ART provides expanded exception detail for java. ClassNotFoundExceptionand java. Later versions of Dalvik provided expanded exception detail for java.

ArrayStoreExceptionwhich now include the size of the array and the out-of-bounds offset, and ART does this as well.

NullPointerException now shows information about what the app was trying to do with the null pointer, such as the field the app was trying to write to, or the method it was trying calvik call. Here are some typical examples:. ART also provides improved context information in app native crash reports, by including both Java and native stack information.

Include an adb bugreport and link to the app in Google Play store if available. Otherwise, if possible, attach an APK that reproduces the issue.

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ART and Dalvik | Android Open Source Project

Content and code samples on this page are subject to the licenses described in the Content License. Improved garbage collection Garbage collection GC can impair an app’s performance, resulting in choppy display, poor UI responsiveness, and other problems.

ART improves garbage collection in several ways: Support for sampling profiler Historically, developers have used the Traceview tool designed for tracing application execution as a profiler.

Support for more debugging features ART supports a number of new debugging options, particularly in monitor- and garbage collection-related functionality. For example, you can: See what locks are held in stack traces, then jump to the thread that holds a lock.

Ask how many live instances there are of a given class, ask to see the instances, and see what references are keeping an object androif. Filter events like breakpoint for a specific instance. Improved diagnostic detail in exceptions and crash reports ART gives you as much context and detail as possible when runtime exceptions occur. Here are some typical examples: Attempt to write to field ‘int android. Attempt to invoke virtual method ‘java.