64-Bit Support

ART was designed in mind with modularity of the various target architectures in which it is supposed to run on. As such, it provides a multitude of compiler-backends targeting today’s most common architectures such as ARM, x86 and MIPS. In addition, 64-bit support for ARM64, x86-64 and while still not implemented, also MIPS64.

While we have gone more in depth of the advantages and implications of switching over to 64-bit architectures in the iPhone 5s review, the main points to take away are the availability of an increased address space, generally increased performance, and vastly increased cryptographic capabilities and performance, all while maintaining full 32-bit compatibility with all existing apps.

An important difference that Google is applying over Apple, at least inside VM runtime applications, is that they are using reference compression to avoid the usual memory bloat that comes with the switch to 64-bit. The VM retains simple 32-bit references.

Google has made available some preview benchmarks showcasing the performance gains both on x86 and ARM platforms. The x86 benchmarks were executed on a Intel BayTrail system, and show a 2x to 4.5x speedup in various RenderScript benchmarks. On the ARM side, the crypto performance gains over 32-bit were showcased on an A57/A53 system. Both of these are relatively non-representative of one should really expect in real-world use-cases so they’re not that useful as a performance prediction.

However Google also made some interesting numbers available on one of their internal build-systems called Panorama. Here we can see a 13 to 19% increase in performance by simply switching over the ABI. It is also good to see how ARM’s Cortex A53 is able to make a bigger impact on performance when in AArch64 mode than the A57 cores.

Google claims that 85% of all current Play Store apps are immediately ready to switch over to 64 bit - which would mean that only 15% of applications have some kind of native code that needs targeted recompiling by the developer to make use of 64-bit architectures. This is a great win for Google and I expect the shift over to 64-bit to be very fast once silicon vendors start shipping 64-bit SoCs in the coming year.


In many points, Google has delivered its “Performance boosting thing” and addressed much of the shortcomings that have plagued Android for years.

ART patches up many of the Achilles’ heels that comes with running non-native applications and having an automatic memory management system. As a developer, I couldn’t have asked for more, and most performance issues that I needed to work around with clever programming no longer pose such a drastic problem anymore.

This also means that Android is finally able to compete with iOS in terms of application fluidity and performance, a big win for the consumer.

Google still promises to evolve ART in the future and its current state is definitely not what it was 6 months ago, and definitely not what it will be once the L release is made available in its final form in devices. The future looks bright and I can’t wait to see what Google will do with its new runtime.

Garbage Collection: Theory and Practice
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  • PearlCParks - Thursday, July 3, 2014 - link

    Contrary to other mobile platforms such as iOS, Windows or Tizen, whjich run software compiled natively to their specific hardwware architecture, the majority of Android software is based around a generic code language whicjh is transformed from “byte-code” into native insstructions for the hardware on the device itself. The performance gains over Dalvik are significant http://num.to/427-837-276-945
  • Filiprino - Saturday, July 5, 2014 - link

    <i>they are using reference compression to avoid the usual memory bloat that comes with the switch to 64-bit. The VM retains simple 32-bit references.</i>
    This feature was implemented in JDK6. Google just imported it into their new VM once ARMv8 (ARM 64 bit) has become available.
    Still, 64 bit android applications will use more memory, if they're compiled by ART for 64 bits.
  • Filiprino - Saturday, July 5, 2014 - link

    But that will probably be outweighted by this:

    Because ART compiles an ELF executable, the kernel is now able to handle page handling of code pages - this results in possibly much better memory management, and less memory usage too. I’m curious what the effect of KSM (Kernel same-page merging) has on ART, it’s definitely something to keep an eye on.

    Also, the work won't end with this release. Like Dalvik before, ART will be improved as time goes by.
  • editorsorgtfo - Monday, July 7, 2014 - link

    "vast increases in available storage space on today’s devices"
    Oh, you mean the vast increase to 16 GB on the Galaxy S5, the same as my iPhone 3GS from 2009?
  • LetsGo - Wednesday, July 9, 2014 - link

    You do know Samsung Galaxy S5 has an memory slot that can handle 128GB cards.

    Thought not You're a Apple user.
  • editorsorgtfo - Wednesday, July 9, 2014 - link

    Google ruined that in KitKat.
  • chadwilson - Tuesday, July 8, 2014 - link

    "and is at the whim of the system to correctly manage things in an optimal manner"

    You're showing your bias. Aside from large heaps, show me where the JVM is not handling memory in an optimal manner, and to clarify this should from a cost benefit perspective outweigh the time it would take to implement in a lower level language.
  • NetMage - Tuesday, July 8, 2014 - link

    Millions pay the penalty thousands of times for successful programs - I think lots of development time could be justified if you looked at everyone's time. Imagine Android not needing so many tries at optimization and speed-up, and how that development time could have been spent instead.
  • goobersnatcher - Saturday, July 12, 2014 - link

    Shortly after updating to Kiit Kat 4.4.4. on my Nexus 5, I switched to ART. It took about 10 minutes to recompile. I really didn't notice any significant storage loss. However, I notice significant improvement in speed and overall responsiveness. For me, very noticeable at first but now that it's become norm ..... as it should be. The N5 is already fast but since ART .... it flies. Stock Kit Kat with ART on 4.4.on a Nexus 5 just smokes. Love it!
  • Peichen - Tuesday, July 15, 2014 - link

    Now would be a very good time those Android liers to come out and admit the old Android simply isn't up to iPhone's standard. I would know, I believed their lies and bought a Note 3 and it lags like I am using a single core computer back in the 2000s.

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