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    <p>To answer one of your questions, the <a href="http://en.wikipedia.org/wiki/Dalvik_(software)" rel="noreferrer">Dalvik VM</a> indeed does use a tracing garbage collector, using a <a href="http://www.brpreiss.com/books/opus5/html/page424.html" rel="noreferrer">Mark and Sweep</a> approach.</p> <p>According to <a href="http://show.docjava.com/posterous/file/2012/12/10222640-The_Dalvik_Virtual_Machine.pdf" rel="noreferrer">The Dalvik Virtual Machine Architecture</a>:</p> <blockquote> <p>The current strategy in the Dalvik garbage collector is to keep mark bits, or the bits that indicate that a particular object is “reachable” and therefore should not be garbage collected, separate from other heap memory.</p> </blockquote> <p>From Android 5.0 (Lollipop) and on, Dalvik was replaced with the <a href="https://en.wikipedia.org/wiki/Android_Runtime)" rel="noreferrer">Android Runtime (ART)</a>.</p> <p>Google has the following to say about the changes in the garbage collector from Dalvik to ART <sup>(<a href="https://source.android.com/devices/tech/dalvik/index.html#Improved_GC" rel="noreferrer">source</a>)</sup>:</p> <blockquote> <h2>Improved garbage collection</h2> <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 GC_FOR_ALLOC events extremely rare in typical use cases Compacting GC to reduce background memory usage and fragmentation</li> </ul> </blockquote> <p>See also:</p> <ul> <li><a href="https://android.googlesource.com/platform/dalvik.git/+/android-4.3_r2/vm/alloc/MarkSweep.cpp" rel="noreferrer">The source code of the Dalvik garbage collector</a></li> <li><a href="https://android.googlesource.com/platform/art/+/master/runtime/gc/" rel="noreferrer">The source code of the ART garbage collector</a></li> </ul>
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    1. POTechnical details of Android Garbage Collector
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    1. USSebastian Paaske Tørholm
    1. USSebastian Paaske Tørholm
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    1. COI take it from your great links that "The main disadvantage of the mark-and-sweep approach is the fact that that normal program execution is suspended while the garbage collection algorithm runs. In particular, this can be a problem in a program that interacts with a human user or that must satisfy real-time execution constraints. For example, an interactive application that uses mark-and-sweep garbage collection becomes unresponsive periodically." Would be interesting to find technical details on how and to what extent Honeycomb's support for multiprocessors can mitigate this disadvantage!?
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      1. USvaiomike
    2. COSo there's no copying involved whatsoever between heap spaces (e.g. from eden space to other spaces?) i.o.w. Android's GC does not use any form of generational/statistical collection strategies?
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    3. COLooking at the source code, I see its marking white, black and grey, so it appears to be tri-color marking.
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      1. USLucy
 

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