Google added a new ART runtime with Android 4.4. How can I target my apk to both ART runtime and Dalvik runtime?
This change is without consequences for the developers. Your app remains exactly the same, nothing to do there. Just make sure you target API 19 so that your app is available for KitKat users. They will decide in their phone if they want to use ART or Dalvik.
This is an old question now, but very key. I confirmed today, all my apps break with ART+Android-5 on Nexus-x tablets. ART does more strict JNI checks, so if your app uses java plus native code,the move from Dalvik to ART may break app operation. For me, it has been a complete show-stop. I have 6 apps in Google Store and all fail now on Nexus devices running Android 5.x, yet they run correctly on all 4.x.x (Kitkat) series devices. This is most frustrating. I am going thru all the ART/ Dalvik questions and answers on this site. ART and Android-5.x is very significant change, so the question asked here "How do I target my apk to both Dalvik and ART?" is a key and very critical question. Time has proven that the responses given suggesting "No difference to developers" is manifestly incorrect. It certainly is in our case.
Two specific issues are documented, and I quote from "Verifying App Behavior on the Android Runtime (ART)":
1) " Checking JNI code for garbage-collection issues
ART has a compacting garbage collector under development on the Android Open Source Project (AOSP). Once the compacting garbage collector is in use, objects may be moved in memory. If you use C/C++ code, do not perform operations that are incompatible with compacting GC. We have enhanced CheckJNI to identify some potential issues (as described in JNI Local Reference Changes in ICS)." In other words, the new ART memory mangement model may break your existing (and operational) native code.
2) " Error handling
ART's JNI throws errors in a number of cases where Dalvik didn’t.".
A limited explanation of some of the issues that will cause errors to be thrown by the Android 5.x ART is provided in: http://developer.android.com/guide/practices/verifying-apps-art.html#JNI_Issues
The forward-compatibility solution currently being adopted among users of Android devices running ART and 5.x, and facing non-operational apps, is a downgrade to Android 4.4.4, by unlocking the bootloader, wiping the device memory, and installing system image "Hammerhead", in the case of those running Nexus series tablets. For Samsung tablets, a tutorial is available at: http://forums.androidcentral.com/samsung-galaxy-s5/489071-tutorial-downgrade-samsung-galaxy-s5-5-0-4-4-kitkat.html
The dalvik or ART is only the runtime in the Android. As an app developer, you don't have to care about these differences. All you have to care about is your app's API level which is describing the dependence of the Android OS version.
And in Android 4.4, ART is only a development which is NOT the default runtime even if the release note describing that ART will make app use less memory and run quickly. If you want to find the different, you can wait for the next version of Android. In the opensource, I found the ART has been setting the default runtime selection.
For most apps ART will work just fine.
It is, however, not 100% compatible as something that work on Dalvik may not work on ART
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Related
I am currently exploring garbage collection on Android. I want to know which garbage collection exactly (ART or Dalvik or whatever else) is used on my phone (Pixel 2, Android 10) so I can read up on how it works (e.g. if it uses a generational approach etc.) So, how can I find out which garbage collection my phone uses?
ART has been the Android runtime on Android devices since Android 5.0.
Note that ART's GC algorithms get tweaked every so often, just as Dalvik's were.
What is Dalvik?
Dalvik is a Just In Time (JIT) compiler. By the term JIT, we mean to say that whenever you run your app in your mobile device then that part of your code that is needed for execution of your app will only be compiled at that moment and rest of the code will be compiled in the future when needed.
What is ART?
ART or Android Runtime is an Android runtime that uses Ahead Of Time(AOT). By using AOT, what is does is it converts or compiles the whole High-level language code into Machine level code and at the time of installation of the app and not dynamically as the application runs(like in case of Dalvik).
Conclusion
Dalvik uses JIT and have a lot of drawbacks that were replaced by ART. So, from Android 4.4(Kitkat) ART was introduced as runtime and finally from Android 5.0(Lollipop), the Dalvik was completely replaced by ART by Android.
About your phone
Pixel 2, Android 10 is above Android Version 5.0, so it is definitely using ART.
I am heard that now Google start using ART, a new run-time for executing Android app and its come with Android 4.4 (in some devices). Now I am just want to confirm that, is pro-grammatically any changes are required or not in existing application or their is any criteria for making new application i.e. run on Dalvik but also compatible with ART ?
I am heard that now Google start using ART, a new run-time for executing Android app and its come with Android 4.4 (in some devices)
ART is not enabled by default on Android 4.4. It is enabled by default on the "L" Developer Preview. It probably will be enabled by default on whatever the next production release of Android is.
is pro-grammatically any changes are required or not in existing application or their is any criteria for making new application i.e. run on Dalvik but also compatible with ART ?
Quoting the documentation (emphasis added):
This document lets you know about things to watch for when migrating an existing app to be compatible with ART. Most apps should just work when running with ART. However, some techniques that work on Dalvik do not work on ART. This document discusses some of these issues.
If you are using the NDK, there's a chance you will need to make some ART-related adjustments. After that, the scenarios in which you would have to change for ART get fairly esoteric.
I've been seeing reports (rumours) that soon Android will be switching from Dalvik to ART as it's default runtime. I have no real idea what that means, my guess the runtime is (kind of?) like the operation system.
My app doesn't do anything particularly special/unique in the sense of mostly it makes HTTP requests for data, and uses LocationListeners a few times.
On some articles I've read about the rumored change, I've seen some people saying things along the lines of "I like ART, I'd use it right now if X app supported it". (One app I remember being mentioned is Xposed)
I've switched my phone to ART, and my app seems to work fine, so I'm guessing the answer to the title question is no, but I'm curious as to how the Xposed app isn't compatible. What have they done (or not done) to make their app not work in ART?
ART is a different runtime for Android applications. All android apps run inside of a virtual machine, much like java code runs in the Java VM.
Classically, when you compiled an Android app, it would compile to Dalvik byte code, designed to run in the Dalvik runtime (virtual machine).
In Android Kitkat though, Google introduced a new experimental runtime called Android Runtime, or ART. This is a different virtual machine, a re-implementaton of the runtime for Android applications to help fix some of the fundamental flaws in the original design.
ART offers several advantages over Dalvik:
Ahead-of-time (AOT) compilation
Improved garbage collection
Development and debugging improvements
Support for sampling profiler
Support for more debugging features
Improved diagnostic detail in exceptions and crash reports
It should also help with things like the DEX limit.
As to your question, you do not need to do anything as a developer. Google has said plainly that "Dalvik must remain the default runtime or you risk breaking your Android implementations and third-party applications".
Google has announced at Google I/O 2014 that in the Android "L" release and beyond, that ART will replace Dalvik.
ART has now replaced Dalvik on the Nexus devices, and my six existing apps, available in the Google Store, all now fail to run. I see multiple lists of questions about ART causing app failures. I suspect the "new and improved" memory managment garbage-collection is the root cause of much of this. My Samsung devices did not have an option to select ART instead of Dalvik, so I am only now getting user reports of the failures under Android 5.x. It is reported that the implementation of the native interface is significantly less forgiving, and requires different and more explicitly defined global pointers, where previously local pointers would operate correctly. This means anyone using native code, and the JNI (native interface), may have to re-code their app, or target a different platform with a more stable system architecture.
After filling the application in Google Play for beta testing began to notice that people with Android 4.4 and a virtual machine ART application simply can not run. Is it possible to somehow add support for this virtual machine?
The ART virtual machine should simply run your app without errors; you don't specifically need to "add" support for it. If it has bugs that prevent your app from working (or your app has bugs that are only exposed by ART), then you'll need to get an Android 4.4 device and test it out. There are instructions here: https://android.stackexchange.com/questions/56773/dalvik-vm-vs-art-android-runtime-for-endusers on how to enable it.
ART is in experimental preview exactly so that developers can try it out and make sure there are no issues preventing their app from working before it's enabled by default for all users in a future Android release.
If you suspect it's an ART bug that's keeping your app from working, file a bug at https://code.google.com/p/android/issues/entry and provide complete details on how to reproduce. It would be most helpful if you could narrow down the problem to what ART's specifically doing wrong instead of just filing a bug that says "my app doesn't work".
I am developing a rather large software on Android with a log native code, it's working now but having some performance issues.
I am hoping I can profile each module(function call) of the software for CPU cycles, memory usage, etc, on several real android phones. Is there a simple c library to do that?
I see people using oprofile, It seems to be a overkill for my case since that it is a system wild profiler, and it requires rebuild the kernel and system image.
As I have the full source code of my app, all I really need is a simple c library that I can embed in my code to do some profiling while the app runs several test cases.
BTW, what is the Linux way of doing this?
I've had pretty decent results with android-ndk-profiler.
http://code.google.com/p/android-ndk-profiler/
Outputs /mnt/sdcard/gmon.out