1 files changed, 139 insertions, 13 deletions
diff --git a/src/devices/tech/dalvik/index.jd b/src/devices/tech/dalvik/index.jd
index 71324d8a..ed1bad11 100644
--- a/src/devices/tech/dalvik/index.jd
+++ b/src/devices/tech/dalvik/index.jd
@@ -1,8 +1,8 @@
-page.title=Dalvik Technical Information
+page.title=ART and Dalvik
 @jd:body
 
 <!--
-    Copyright 2013 The Android Open Source Project
+    Copyright 2014 The Android Open Source Project
 
     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.
@@ -16,14 +16,140 @@ page.title=Dalvik Technical Information
     See the License for the specific language governing permissions and
     limitations under the License.
 -->
-<p>Dalvik is the managed runtime used by applications and some system
-services on Android. Dalvik was originally created specifically for
-the Android project.</p>
-<p>Much of the documentation in this directory is intended to help
-with the ongoing development of Dalvik, as opposed to most of the
-other documentation on this site, which is geared more towards
-application development.</p>
-
-<p>Please note, in Android 4.4 a new virtual machine - ART - is being introduced
-experimentally that will eventually replace Dalvik. Please see <a
-href="{@docRoot}devices/tech/dalvik/art.html">Introducing ART</a> for details.
+
+
+<div id="qv-wrapper">
+<div id="qv">
+  <h2 id="Contents">In this document</h2>
+  <ol id="auto-toc">
+  </ol>
+</div>
+</div>
+
+<p>Android runtime (ART) 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. ART as the runtime executes the Dalvik
+Executable format and Dex bytecode specification.</p>
+
+<p>ART and Dalvik are compatible runtimes running Dex bytecode, so apps
+developed for Dalvik should work when running with ART. However, some
+techniques that work on Dalvik do not work on ART. For information about the
+most important issues, see <a
+href="http://developer.android.com/guide/practices/verifying-apps-art.html">Verifying
+App Behavior on the Android Runtime (ART)</a>.</p>
+
+<h2 id="features">ART Features</h2>
+
+<p>Here are some of the major features implemented by ART.</p>
+
+<h3 id="AOT_compilation">Ahead-of-time (AOT) compilation</h3>
+
+<p>ART introduces ahead-of-time (AOT) compilation, which can improve app
+performance. ART also has tighter install-time verification than Dalvik.</p>
+
+<p>At install time, ART compiles apps using the on-device
+<strong>dex2oat</strong> tool. This utility accepts <a
+href="http://source.android.com/devices/tech/dalvik/dex-format.html">DEX</a> files as input and
+generates a compiled app executable for the target device. The utility should be
+able to compile all valid DEX files without difficulty. However, some
+post-processing tools produce invalid files that may be tolerated by Dalvik but
+cannot be compiled by ART. For more information, see  <a
+href="http://developer.android.com/guide/practices/verifying-apps-art.html#GC_Migration">Addressing
+Garbage Collection Issues</a>.</p>
+
+<h3 id="Improved_GC">Improved garbage collection</h3>
+
+<p>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:</p>
+
+<ul>
+  <li>One GC pause instead of two</li>
+  <li>Parallelized processing during the remaining GC pause</li>
+  <li>Collector with lower total GC time for the special case of cleaning up
+  recently-allocated, short-lived objects</li>
+  <li>Improved garbage collection ergonomics, making concurrent garbage
+  collections more timely, which makes <a
+  href="http://developer.android.com/tools/debugging/debugging-memory.html#LogMessages"><code>GC_FOR_ALLOC</code></a>
+  events extremely rare in typical use cases</li>
+  <li>Compacting GC to reduce background memory usage and fragmentation</li>
+</ul>
+
+<h3 id="Debugging_Imp">Development and debugging improvements</h3>
+
+<p>ART offers a number of features to improve app development and debugging.</p>
+
+<h4 id="Sampling_Profiler">Support for sampling profiler</h4>
+
+<p>Historically, developers have used the <a
+href=" http://developer.android.com/tools/help/traceview.html">Traceview</a>
+tool (designed for tracing
+application execution) as a profiler. 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.</p>
+
+<p>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.</p>
+
+<h4 id="Debugging_Features">Support for more debugging features</h4>
+
+<p>ART supports a number of new debugging options, particularly in monitor- and
+garbage collection-related functionality. For example, you can:</p>
+
+<ul>
+  <li>See what locks are held in stack traces, then jump to the thread that
+      holds a lock.</li>
+  <li>Ask how many live instances there are of a given class, ask to see the
+      instances, and see what references are keeping an object live.</li>
+  <li>Filter events (like breakpoint) for a specific instance.</li>
+  <li>See the value returned by a method when it exits (using “method-exit”
+      events).</li>
+  <li>Set field watchpoint to suspend the execution of a program when a specific
+      field is accessed and/or modified.</li>
+</ul>
+
+<h4 id="Crash_Reports">Improved diagnostic detail in exceptions and crash reports</h4>
+
+<p>ART gives you as much context and detail as possible when runtime exceptions
+occur.  ART provides expanded exception detail for <code><a
+href="http://developer.android.com/reference/java/lang/ClassCastException.html">java.lang.ClassCastException</a></code>,
+<code><a
+href="http://developer.android.com/reference/java/lang/ClassNotFoundException.html">java.lang.ClassNotFoundException</a></code>,
+and <code><a
+href="http://developer.android.com/reference/java/lang/NullPointerException.html">java.lang.NullPointerException</a></code>.
+(Later versions of Dalvik provided expanded exception detail for <code><a
+href="http://developer.android.com/reference/java/lang/ArrayIndexOutOfBoundsException.html">java.lang.ArrayIndexOutOfBoundsException</a></code>
+and <code><a
+href="http://developer.android.com/reference/java/lang/ArrayStoreException.html">java.lang.ArrayStoreException</a></code>,
+which now include the size of the array and the out-of-bounds offset, and ART
+does this as well.)</p>
+
+<p>For example, <code><a
+href="http://developer.android.com/reference/java/lang/NullPointerException.html">java.lang.NullPointerException</a></code>
+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 to
+call. Here are some typical examples:</p>
+
+<pre class="no-pretty-print">
+java.lang.NullPointerException: Attempt to write to field 'int
+android.accessibilityservice.AccessibilityServiceInfo.flags' on a null object
+reference</pre>
+
+<pre class="no-pretty-print">
+java.lang.NullPointerException: Attempt to invoke virtual method
+'java.lang.String java.lang.Object.toString()' on a null object reference</pre>
+
+<p>ART also provides improved context information in app native crash reports,
+by including both Java and native stack information. </p>
+
+<h2 id="Reporting_Problems">Reporting Problems</h2>
+
+<p>If you run into any issues that aren’t due to app JNI issues, please report
+them via the Android Open Source Project Issue Tracker at <a
+href="http://b.android.com">http://b.android.com</a>.
+Please include an <code>"adb bugreport"</code> and link to the app in Google
+Play store if available. Otherwise, if possible, attach an APK that reproduces
+the issue. Please note that issues (including attachments) are publicly
+visible.</p>