Technical interpretation of Android L:art virtual machine greatly improve the operating efficiency of the system

in San Francisco, California

Editor's note: This article from the Leopard Cleaning Master's technical engineer to contribute, from the system operating efficiency, system security, privacy protection, to Google just released the Android L do some technical interpretation.

The first two days of Google's 2014 GOOGLEI/O conference at the Moscone Center in San Francisco, California, were dubbed "Android takes over", especially in the most heavyweight Android L, in addition to the launch of a full platform "Material Design style, Google also has a directional deployment of Android's underlying core technology, including art, security, and power saving, among other key areas of optimization.

Android l defaults to art running environment, fully compatible with 64-bit mobile processors. Google says it will be twice times better than the previous Dalvik mode, but will consume more memory. Android has three modes of operation: JNI, Dalvik, ART. Dalvik is obviously the slowest, the full JNI model is the fastest but the development is difficult, art is somewhere in between, and it doesn't affect the existing development model, so Google chose art. Our technical engineers have made a technical interpretation of this:

1 JNI: In the development process using the compiler in C + + and other languages directly compiled into machine code, the runtime can take full advantage of system performance, this is the fastest. The NDK of iOS's Object C and Android are all in this mode.

2 dalvik:android L System before all the Android version of the operation, using bytecode, in the run-time interpretation of the execution into machine can recognize the machine code. This process is relatively slow.

3 Art:android 4.4 began to launch the new operating environment, in the app installation using the Dex2oat tool to directly convert Dex file to machine code files, running in machine code mode, can make full use of system performance; The improved memory recovery mechanism makes the memory recovery speed in art running mode only 50% under the Dalvik mode, and can also improve the running speed of the system.

Although the speed of the operation has increased, art has its drawbacks:

1 The app installation process slows down;

2 The app occupies more storage space and the system is more prone to lack of space.

Google has mentioned the importance of Android security this year, but the Android L system still has some congenitally deficient:

1 malware and virus continues to grow

Android system has been born, has been plagued by a variety of malware attacks, with various operating system ROM pre-installed built-in and application of the market audit lax and so on, the Android platform malware and the number of viruses in a straight upward trend. We began 5 years ago to focus on the malicious behavior of various kinds of software on Android, set up the app behavior cloud, and analyze the behavior of various kinds of app with static and dynamic method.

According to the CM security monitoring data, a total of more than 4.5 million malicious samples were found, including malware and viruses. In the first half of 2014, these two growth trends than the 150%,android platform Security war is a protracted battle.

2 system and Third-party software vulnerabilities only Google patch is not enough

The Android L system adds googleplay support for system patches, but because of the fragmented distribution of the Android version and the various custom system ROM, not all vulnerabilities can be patched by GooglePlay. And for the Third-party software running on the Android system, there are a number of vulnerabilities (such as WhatsApp privacy leaks, Adobe Reader's webview arbitrary code execution vulnerabilities, and so on), for these vulnerabilities risk, tightly rely on googleplay patch mechanism, is unavoidable or fully patched, the risks of Android vulnerabilities remain grim.

3 The security of mobile phone is increasingly important

U.S. legislation has pushed smartphone support against theft, which has been enhanced in the Android L system to completely prevent two of reselling or information theft after a phone theft. According to the US Consumer report (Consumer Reports), more than 3 million smartphones were stolen in the US in 2013, up from 1.6 million in the 2012-year period.

4 Privacy protection mechanism education takes time

About 200,000 applications (about 4.4%) based on the cloud analysis of app behavior in the CM security laboratory The user will be asked for unnecessary privacy rights, such as SMS, call records read and write permissions, user location data permissions. These apps secretly get the user's privacy in the background, resulting in the user's daily whereabouts exposed.

The Android l system provides a mechanism to adjust app permissions to avoid the risk of user privacy disclosure. For the most common users, learning how to do the underlying settings to manage app permissions also requires a certain educational cycle.