KR20110081723A - Hybrid Java Compilation System for Digital TV Software Platforms - Google Patents

Abstract

PURPOSE: A hybrid JAVA compile system for a DTV(Digital Television) software platform is provided to apply a different compile mode to a system, a middleware class, and an xlet application according to each characteristic of the system, the middleware class, and the xlet application. CONSTITUTION: A system and middleware method administration module(100) administrates a machine code which is previously compiled and installed. An xlet application receiving module(200) receives an xlet application from a broadcast station. An xlet application compile module(300) compiles the received xlet application using a JITC(Just-In-Time Compile) mode. A JAVA application execution module(400) executes a JAVA application using the machine code for the complied xlet application.

Description

Hybrid Java Compilation System for Digital TV Software Platforms

The present invention relates to a Java compilation system for a digital TV software platform, and more particularly to a hybrid Java compilation system for a digital TV software platform that applies different compilation schemes for the system and middleware classes and xlet applications.

Unlike conventional analog TV, digital TV receives broadcast signals through digital signals. Digital broadcasting technology can transmit a signal using a low frequency bandwidth using video compression technology to reproduce a high-definition screen. It uses the remaining bandwidth to transmit data, which provides an interactive TV (i.e., interactive TV, iTV) environment where general information such as traffic, weather, news, and stocks can be provided, or viewers can request services. I can build it.

Java is an important technology for data broadcasting, and many iTV standards use Java. It uses Java xlet applications to broadcast data, which consists of xlet classes and image and text files. Java xlet applications are received by DTV set-top boxes via digital broadcast signals and run with the system and middleware classes in the set-top box to output information to the screen. Therefore, DTV's software platform is divided into system and middleware class pre-installed in set-top box and xlet class delivered through broadcasting.

In order to improve the performance of such a DTV platform, a general method of converting Java bytecode into machine code is executed by a just-in-time compiler (JITC). However, for the greater performance of the DTV platform, compared to JITC, the DTV platform has a ahead-of-time compiler (AOTC) that can generate good code with no running overhead and more optimization. There is a need to apply it.

The present invention has been proposed to solve the above problems of the conventionally proposed methods, and improves performance compared to the existing compilation system by applying different compilation schemes for the characteristics of the system and the middleware class and the xlet application. Its purpose is to provide a hybrid Java compilation system for the digital TV software platform that can be obtained.

According to a feature of the present invention for achieving the above object, a hybrid Java compilation system for a digital TV software platform,

(1) a system and middleware method management module that manages machine code precompiled and installed on the server side using an Ahead-Of-Time Compile (AOTC) method for the system and middleware methods;

(2) an xlet application receiving module for receiving an xlet application from a broadcast station;

(3) an xlet application compilation module that compiles an xlet application received through the xlet application receiving module during execution using a Just-In-Time Compile (JITC) scheme when a predetermined condition is satisfied; And

(4) a Java application that executes a Java application using machine code for a system and middleware method managed by the system and middleware method management module and machine code for an xlet application compiled by the xlet application compilation module. Including the execution module is characterized by its configuration.

Preferably, in the xlet application compilation module,

When the predetermined condition is satisfied, the number of invocations of the method may be counted with respect to the received xlet application, and the counted number of invocations may exceed a predetermined threshold.

Preferably, the Bytecode-to-C AOTC method which converts bytecode into C code and utilizes a C compiler among the AOTC methods may be used.

According to the hybrid Java compilation system for the digital TV software platform of the present invention, a significant performance improvement can be obtained compared to the existing compilation system by applying different compilation schemes for the respective characteristics to the system and the middleware class and the xlet application.

1 is a diagram showing the configuration of a hybrid Java compilation system for a digital TV software platform according to an embodiment of the present invention.
2 is a diagram illustrating the distribution of the number of methods invoked when an xlet application is run.
3 illustrates the distribution of methods in which JITC is performed when an xlet application is run.
4 and 5 are views showing the result of performing the actual xlet application in the hybrid environment proposed in the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a configuration of a hybrid Java compilation system for a digital TV software platform according to an embodiment of the present invention. As shown in FIG. 1, a hybrid Java compilation system for a digital TV software platform according to an embodiment of the present invention includes a system and middleware method management module 100, an xlet application receiving module 200, and an xlet application compilation module. It may be configured to include a 300 and the Java application execution module 400. In addition, as shown in FIG. 1, the object carousel file management module 500 may further include.

In the present invention, AOTC (Ahead-Of-Time) that installs the converted machine code in the set-top box after pre-compilation on the server side, rather than using a JITC method for compiling in real time during execution on the client side for the system and middleware methods Compile) method is used. The machine code for the system and the middleware method that is converted and installed in the set-top box is managed by the system and the middleware method management module 100. In the present invention, the Bytecode-to-C AOTC method which converts bytecode into C code and utilizes the C compiler is used.

The xlet application receiving module 200 receives an xlet application from a broadcast station. In particular, the xlet application receiving module 200 proposed by the present invention may further include an object carousel file management module which enables the entirety of the xlet application to be restored even if the xlet application starts to be received from the middle.

The xlet application compilation module 300 compiles the xlet application received through the xlet application receiving module 200 during the execution using the Just-In-Time Compile (JITC) method when a predetermined condition is satisfied. Here, the case where the predetermined condition is satisfied may be, for example, a case in which the number of calls of the method is counted for the received xlet application, and the counted number of calls exceeds the predetermined threshold.

The Java application execution module 400 may include machine code for system and middleware methods managed by the system and middleware method management module 100, and machine code for xlet applications compiled by the xlet application compilation module 300. To execute a Java application.

As described above, the hybrid Java compilation system for the digital TV software platform proposed in the present invention is considerably improved in performance compared to the existing compilation system by applying different compilation methods to the system and the middleware class and the xlet application. Can be obtained.

Hereinafter, the hybrid Java compilation system for the digital TV software platform proposed by the present invention, the experiments on the general DTV Java software platform, the hybrid Java compilation system proposed in the present invention, and the hybrid Java compilation system of the present invention. The results will be described in more detail.

1. DTV Java Software Platform

(1) DTV software structure and xlet execution

Our target DTV Java platform is ACAP, which is the standard specification of domestic DTV and IPTV platforms. ACAP, installed on DTV's set-top box, is based on the Globally Executable MHP (GEM) and provides a Java-based application environment as an MHP-based platform.

ACAP allows DTV to receive Java xlet applications for data broadcasting. Java xlet applications typically consist of xlet class files for running programs, image files for screen composition, and text files with actual information. In order to transmit and receive Java xlet applications, a broadcasting station uses a carousel method that divides an application and transmits each part sequentially. DTV set-top boxes require an object carousel file manager that can receive application fragments sequentially and restore the whole even if they start receiving in the middle. This file manager manages the names, properties, directory locations, and version information of the files in the application.

Data broadcasting transmits a unique Java xlet application for each broadcasting station, and is provided through a TV screen along with a screen when watching a corresponding channel, thereby waiting for xlet execution. When the user selects to execute the xlet, the user interface such as a menu is activated on the screen to provide the received information and the interactive service. If the channel is changed or the version of the xlet application on the broadcast signal is updated, the xlet is stopped and a new xlet application is received.

(2) DTV Java execution environment

The special feature of DTV Java is that it executes two types of Java classes from different places. One is the system and middleware classes that were originally pre-installed in the DTV set-top box, and the other is the xlet class that dynamically downloads and executes from broadcast stations. On the one hand, the applications used in these systems have become increasingly complex. Beyond simply displaying information on the screen, it provides content that requires a lot of runtime, such as games and interactive services.

Thus, there is a need for technology that accelerates DTV Java execution. Java is basically compiled into an executable format called bytecode and executed by the interpreter so that it can operate independently on various platforms. Since this implementation is very slow compared to normal machine code execution, the bytecode is converted into machine code using the just-in-time compiler (JITC) or ahead-of-time compiler (AOTC). JITC dynamically compiles classes during execution, and AOTC precompiles and installs the converted machine code on the client.

In general, JITC can be used in DTV environment. This is because AOTC cannot be applied here because xlet is downloaded and used dynamically. However, AOTC has no running overhead and can use machine code with various optimizations beyond the constraints of client resources. Therefore, there is a need to build a hybrid compilation environment using JITC for downloaded xlets and preinstalled systems and middleware classes applying AOTC.

2. Hybrid Java compilation environment

(1) JITC for running Java xlets

The DTV platform we target uses phoneMe Advance, an open source version of Sun's Connected Device Configuration (CDC) JVM. The VM uses adaptive JITC based on Sun's HotSpot technology.

HotSpot technology executes Java method as an interpreter first, and when the method is determined as a hot spot, it converts the method's bytecode into machine code and stores it in the code cache.

In our hybrid Java compilation environment, we apply phoneme Advance's JITC to the xlet method.

(2) AOTC for system and middleware methods

In the present invention, in order to apply AOTC, a method of generating an executable file by converting byte code into C code and compiling the converted code using CVM source code and gcc is used.

This method of converting bytecode to C code and utilizing the C compiler is called bytecode-to-C AOTC. The Bytecode-to-C method can easily utilize optimization techniques already implemented in the compiler by generating machine code using an existing compiler. The translated C code is compiled with the JVM code and becomes one executable.

In order to optimize the code, Java-specific optimizations such as method inlining and repeated null check elimination are implemented and applied. In addition, in the present invention, the compile is performed only for a method that is called more than 25 times among system and middleware methods.

However, Bytecode-to-C type AOTC may incur overhead during function call. This is because the interpreter and JITC use function calls using the Java stack, but AOTC uses the C stack. This call method is optimized between AOTC method calls, but the function calls between the interpreter and JITC and AOTC methods require additional work due to the use of different stacks.

3. Experimental Results

(1) experimental environment

The set-top box constructed with the hybrid Java compilation environment for use in the present invention has a 333MHz MIPS CPU and 128MB of memory. The software platform uses ATSC's ACAP middleware for Sun's phoneMe Advanced MR2 version and runs on the Linux kernel.

The Java xlet application uses what is actually broadcast from the broadcaster and specifies each xlet menu item as A to J. The service outputs news, weather, traffic, stock information, and more. Execution time was measured as the time taken from the selection of the corresponding service through the menu until the screen is displayed.

(2) DTV Java characteristics

First, we looked at the characteristics of DTV Java applications. It was measured using JITC only for the experiment. 2 is a diagram illustrating a distribution of the number of methods called when an xlet application is executed. In FIG. 2, the parts shown in dark black represent xlet methods, the parts shown in dark gray represent system methods, and the parts shown in light gray represent middleware methods, respectively. From Figure 2, it can be seen that in most DTV Java applications, the xlet method is insignificant and most are system and middleware methods.

We also examined the distribution of methods that are frequently called and executed by JITC. 3 shows that the methods compiled by JITC are mainly system and middleware methods (classes) and some are xlet methods. This can be expected to apply AOTC to system and middleware classes (methods).

(3) performance improvement

4 and 5 are diagrams showing the result of performing the actual xlet application in the hybrid environment proposed in the present invention. Figure 4 is a graph showing the execution time, the unit is ,, Figure 5 is a graph showing the performance ratio when using the JITC only 100%. In FIG. 4 and FIG. 5, the dark black part shows the case where JITC is used only, and the light gray part shows the case where JITC and AOTC (bytecode-to-C AOTC) are used together. 4 and 5, it can be seen that the performance improvement in all applications, the average rate of improvement was about 20%. From these results, it can be judged that the optimization of AOTC was sufficiently effective beyond the method call overhead caused by applying bytecode-to-C AOTC.

The present invention described above may be variously modified or applied by those skilled in the art, and the scope of the technical idea according to the present invention should be defined by the following claims.

100: System and middleware method management module
200: xlet application receiving module
300: xlet application compilation module
400: Java application execution module
500: Object Carousel File Management Module

Claims (3)

Hybrid Java compilation system for digital TV software platform,

(1) a system and middleware method management module that manages machine code precompiled and installed on the server side using an Ahead-Of-Time Compile (AOTC) method for the system and middleware methods;
(2) an xlet application receiving module for receiving an xlet application from a broadcast station;
(3) an xlet application compilation module that compiles an xlet application received through the xlet application receiving module during execution using a Just-In-Time Compile (JITC) scheme when a predetermined condition is satisfied; And
(4) a Java application that executes a Java application using machine code for a system and middleware method managed by the system and middleware method management module and machine code for an xlet application compiled by the xlet application compilation module. Perform module

Hybrid Java compilation system for a digital TV software platform comprising a.
The module of claim 1, wherein in the xlet application compilation module:
The hybrid Java for the digital TV software platform is characterized in that, when a predetermined condition is satisfied, the number of times of the method call is counted for the received xlet application, and the counted number of calls exceeds a predetermined threshold. Compilation system.
The method of claim 1,
Hybrid Java compilation system for the digital TV software platform, characterized in that using the Bytecode-to-C AOTC method that converts bytecode to C code in the server side to utilize the C compiler.

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