Welcome!

Linux Containers Authors: Craig Lowell, David Paquette, Elizabeth White, Liz McMillan, AppDynamics Blog

Related Topics: Linux Containers, Java IoT

Linux Containers: Article

Improving Swing Performance: JIT vs AOT Compilation

Linux native band plays fast

The JFC/Swing API, natively precompiled on Linux for the first time, delivers measurable improvement in Java GUI performance.

The Excelsior Engineering Team has ported Excelsior JET, a Java Virtual Machine (JVM) with an ahead-of-time compiler, to the Linux/x86 platform. As the JET JVM supports the entire J2SE platform API including the Java Foundation Classes (JFC/Swing), Excelsior engineers had an opportunity to evaluate the response time of natively compiled JFC/Swing on Linux. The results of the comparison with conventional, dynamically optimizing JVMs were encouraging: response time has improved by 40% or even doubled on some benchmarks. What's more important is that real-world Swing applications performed perceivably faster.

This article describes Excelsior JET JVM and JFCMark, free benchmark software by Excelsior that measures Swing-based GUI performance. Moreover, the authors share their technical experience in optimizing JFC/Swing and argue why ahead-of-time Java compilation has advantages over dynamic compilation for certain application types.

Two Recipes for Java

The definition of the term "virtual machine" has been revised in the past few years. Modern Java Virtual Machines are no longer just interpreters of the Java bytecode. High performance, state-of-the-art implementations are made up of optimizing compilers that translate bytecode instructions down to the native code that runs directly on the hardware. However, one technical decision distinguishes contemporary JVMs: what's the best time to run the performance engine, an optimizing native compiler? Two options exist: run it before or after the application starts.

Most JVMs initially interpret the program and then analyze how it runs by looking for hot spots, that is, frequently executed portions of bytecode. Hot spots are then compiled to optimized native code during program execution. This approach is called Just-In-Time (JIT) compilation. Other JVMs feature static native compilers similar to traditional C/C++ compilers, enabling developers to optimize their Java applications before execution. For Java, this old trick has a new name - Ahead-Of-Time (AOT) compilation. However, solely static compilation is not enough for Java compatibility. Remember that many Java applications use custom classloaders to load some components or plug-ins at runtime. To have the "J" in "JVM," such virtual machines must be supplied with an interpreter or JIT compiler to handle classes that could not be precompiled.

Either approach alone is not a silver bullet for Java performance. JIT-oriented JVMs can "see through" program execution, which may help them optimize hot code better than static compilers do. In return, AOT-oriented JVMs do not spend execution time on interpretation, profiling, and compilation, so optimized programs run fast from start-up. Not surprisingly, single-loop benchmarks fail to reveal a clear performance winner between the two approaches. Instead of carrying the "microbenchmark war" into the Linux camp, let's take a look at a vital example: the performance of Java GUI applications based on JFC/Swing.

Penguin-Driven JVMs

Both JIT and AOT-oriented implementations are available for Linux. The well-known Sun HotSpot Client and Server JVMs are powered by JIT compilers. BEA WebLogic JRockit and IBM Java 2 Runtime Environment also play in the JIT team. GCJ, the GNU compiler for Java, now supported by Red Hat, and Excelsior JET feature AOT compilation.

At the core of Excelsior JET is a static optimizing compiler that enables developers to transform their Java applications into native executables or shared libraries (.so) on a Linux flavor. The AOT compiler comes with a JET Control Panel (see Figure 1), a graphical front end that makes the product easy to learn and use. The command-line interface provides the integration of Excelsior JET into automated builds. The redistributable JET runtime system includes a JIT compiler to support Java dynamic classloading. Another graphical tool, JetPackII (see Figure 2), enables the rapid creation of installation packages for optimized applications. Excelsior JET supports all Java 2 platform packages up to version 1.4.2.

Another static Java compiler is GCJ, a member of the GNU Compiler Collection. Following the FSF philosophy, GCJ uses a clean-room, free implementation of the Java 2 Platform API. Although most packages are now supported, there are noticeable exceptions such as the Abstract Window Toolkit (AWT), Swing, and some of the APIs introduced to J2SE 1.4. Contributors to the GNU Classpath project are currently implementing the missing packages. The GNU Interpreter for Java complements GCJ to enable Java dynamic loading. The implementation of a JIT compiler is planned for the future.

Accelerated Swing Tempo

GUI response time is in the eye of the beholder. As a result, it's tough to obtain GUI performance scores. To address this problem, Excelsior has developed JFCMark, a free benchmark suite to measure the performance of the JFC/Swing API. The included tests are manipulating with frames, trees, and tables; switching look-and-feels; decoding and drawing images; displaying and scrolling HTML texts; and using Swing layout managers. JFCMark requires JVMs that support the Java 2 Platform at the level of J2SE 1.3, 1.4, or 1.5.

Each test performs its scenario in the main loop through a given number of iterations. This allows you to obtain performance scores in short- and long-running modes. Upon completion, these tests report performance measured in units specific to their specific scenarios, for instance, frames opened per second. When designing JFCMark, we paid close attention to benchmarking accuracy. For a particular configuration, every benchmark always performs the same number of operations independently of the JVM under test. This requirement is achieved through synchronous processing of Swing events, that is, a next event is sent only after the previous one is processed. Therefore, a possible difference in reported speed depends solely on the time of the benchmark execution.

Let's consider the performance of the Swing windowing system that provides operations with frames. We have used a part of JFCMark to test typical manipulations with frames such as opening/closing, dragging, and selecting. The testbed configuration was as follows.]

  • CPU: AMD Athlon running at 1,8 GHz
  • RAM: 512MB DDR SDRAM
  • Video: NVidia GeForce2 MX-200 at 1024x768x65536c
  • OS: Red Hat Linux release 8.0 (Psyche)
  • Linux Kernel: 2.4.18-14
We've run these benchmarks using a spectrum of JVMs available for Linux:
  • Excelsior JET 3.6 Professional Edition with JRE 1.4.2_04
  • Sun Java HotSpot Client VM 1.4.2_04
  • IBM J2RE 1.4.2 Classic with JIT enabled
  • Sun Java HotSpot Server VM 1.4.2_04
  • BEA WebLogic JRockit 8.1 with JRE 1.4.2_04
The server-oriented JVMs (Sun HotSpot Server and BEA WebLogic JRockit) are included for your reference. They're not expected to really shine in client-side application performance. GCJ is not included because it does not yet have support for JFC/Swing. To play fair, we provided results for both long- and short-running configuration of the benchmarks. Figures show the composite performance index in comparison with the reference implementation (Sun HotSpot Client VM). Longer bars mean better performance.

Figure 3 shows Swing performance scores for the long-playing version of JFCMark. For example, 600 frames are opened and closed by one of the tests. In this scenario, JIT-based JVMs have a chance to "warm up," that is, to optimize hot code for maximum speed. Note, however, that this level of performance may be reached only after doing a "good amount of mouse-clicking" in real-world Java GUI applications. Nevertheless, Excelsior JET still outperforms by 40% the first runner-up (HotSpot Client VM).

To see how Swing works on dynamic JVMs that have not been "warmed up" yet, look at Figure 4. It shows out-of-the-box performance scores for the short-running configuration. This case would correspond to the way Java GUI applications perform right after start-up. As can be seen, the JET-compiled Swing runs fast and it runs fast from the start. Other test participants work at least twice as slow for this scenario. Note that short-running benchmarks are mostly important for the client-side application's performance. For instance, if you start a GUI application and drag something with the mouse, you don't want to see it stumbling just because the JVM has not yet done its job. People talking about "snail Java" often ignore the fact that many JVMs take time to warm up. It's not an issue for server-side applications, which typically run for hours and days. However, the performance of client-side applications is most heavily impacted by the JVM warm-up cycle.

JEdit, a Practical Example

If you don't trust vendor benchmarks, check the results yourself. One of the samples that comes with Excelsior JET is a project for compiling jEdit, an open source, cross-platform text editor written in Java. jEdit has many advanced features that make text editing easier, such as syntax highlighting, auto indent, abbreviation expansion, registers, macros, regular expressions, and multiple file search/replace. It's a good example of a full-featured Swing-based application to evaluate GUI response time.

Behind the Performance Figures

An interesting question is why don't the JIT-powered JVMs hit the performance bar raised by Excelsior JET? Of course, aggressive static optimizations and the removal of bytecode interpretation make Swing work smoothly. However, it seems that the long-running mode of JFCMark should be comfortable for the JIT compilers. Where does the 40% performance win come from? We found the answer unexpectedly when we aimed at further improving Swing performance: the absence of hot methods.

Under the covers, JFC/Swing is quite a complex event-driven system implemented on top of AWT. The implementation consists of several hundred classes which, in turn, use a variety of other core classes. Many thousands of Java methods are executed when, for example, you open a Swing frame. When we obtained the Swing execution profile, it proved to be almost flat. Lots of methods were executed but each of them took hundredths of one percent in total execution time. Only a few methods took more than 1-2%. At this point, we encountered an interesting problem: what should we improve in the absence of clear performance bottlenecks? As you may have guessed, the same problem exists for profile-guided JIT compilers. Instead of a few hot spots to be aggressively optimized, there are plenty of "warm spots" that are left intact. The flat execution profile is an application-specific property that some JVMs cannot effectively manage to achieve top performance.

Conclusion

This article is not about fast and slow JVMs. Rather, it demonstrates that for some Java applications, a JVM with AOT compilation can work faster than JIT-based JVMs. The main lesson we have learned from this study is that one size does not fit all and JFC/Swing is not the only example. One way or another, the Java platform wins and we were happy to make Excelsior JET JVM available to Java/Linux developers.

Resources

  • Java Foundation Classes (JFC/Swing): http://java.sun.com/products/jfc/
  • Excelsior JET: www.excelsior-usa.com/jet.html
  • JFCMark: JFC/Swing benchmark with source code: www.excelsior-usa.com/jfcmark.html
  • Sun HotSpot JVMs: http://java.sun.com/j2se/1.4.2
  • IBM J2RE: www-106.ibm.com/developerworks/java/jdk/linux140/
  • BEA WebLogic JRockit: www.bea.com/framework.jsp?CNT=index.htm&FP=/content/products/jrockit
  • GCJ, the GNU compiler for Java: http://gcc.gnu.org/java/
  • GNU Classpath: www.gnu.org/software/classpath/
  • jEdit: www.jedit.org
  • More Stories By Vitaly Mikheev

    Vitaly Mikheev is the chief technology officer for Excelsior, LLC, a company focusing on design and development of optimizing compilers. Vitaly has been involved in software development since 1987 and focused on compiler construction technologies for the last decade. He started working with Java in 1998 as the architect of the Excelsior Java Virtual Machine. Before that, he worked on proprietary optimizing compilers for Nortel Networks. Vitaly is a member of ACM and a co-author of the patent on the garbage collector algorithm implemented in the Samsung's J2ME CDC virtual machine. He holds an MS in computer science from the Novosibirsk State University, Russia.

    Comments (5) View Comments

    Share your thoughts on this story.

    Add your comment
    You must be signed in to add a comment. Sign-in | Register

    In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


    Most Recent Comments
    Blind Earl 11/08/04 09:04:35 AM EST

    Once I actually found the article it was an interesting read. However, this website looks *terrible*. When a column is only 11 characters wide due to advertising squishing it down, it is time to find some other magazine to read.

    the author 11/08/04 07:14:08 AM EST

    To angel'o'sphere:

    1)

    >>A VM based on a JIT compiler loads always only byte code
    >>and compiles the byte-code to native code on the fly
    >>depending on several algorithms/heuristics.
    >>A AOT compiler does JUST THE SAME on the first invocation
    >>of the byte code program, but it saves the generated
    >>native code to be available for later invocations of the
    >>same program. So for the later invocations, the
    >>compilation was ahead of time, not for the first one

    The thing you are talking about is called Caching JIT compilation (at least HotSpot and BEA engineers called it so when I talked with them at JavaOne 2004)

    Besides, Caching JIT compilation does not occur on the first invocation - it would take long long time and miss profile information useful for optimizations.

    2)

    >>The Excelsior JET is no AOT compiler but just a static
    >>compiler. However they seem to jump on the bandwagon
    >>of a new buzzword, because the term AOT is only used
    >>in academic circles currently

    visit http://gcc.gnu.org/java/ (GNU compiler for Java). It's described as an AOT compiler...

    3)

    >>The next flaw is this: they measure a GUI application
    >>over only 600 "loops". As the exact form of the loop
    >>is not published, I have the impression they made the
    >>loop in a way that a "standard" HotSpot JIT does
    >>predictable not even attempt to compile much of the
    >>covered code

    In this test, HotSpot shows 28,9 frames/sec for short-running configuration and 44,6 frames/sec for long-running one. It does not look like "not even attempt to compile much of the covered code". Increasing the number of iteration to open more frames does not improve the HotSpot results. BTW, did you ever open 600+ frames in a Java application?

    4)

    >>In the "benchmark" of the article,
    >>you neither have a loop (that one is in the external
    >>driver program hidden) nor stack samples which occur
    >>often enough to cause a JIT compilation.

    Check the source code of the benchmark. It includes the loop

    for(int j=0;j>IMHO: the Excelsior people tricked the HotSpot/JIT VMs
    >>in not doing their job, and thus you see the big
    >>performance gain.
    >> There are other tricks thinkable, e.g. not using
    >>the standard SWING library but a tweaked one,
    >>just remove some "synchronized" keywords if
    >> you are sure the benchmark does not need them,
    >> and voila ...

    The standard Swing library and the public JET version were used for benchmarking. As for "synchronized" keywords - some of them are *safely* removed by the JET compiler during the course of escape analysis. There is excellent literature about this optimization technique (for example, see ACM OOPSLA'99 - about 5 papers were devoted to it).

    Take care,

    --Vitaly

    P.S. JITs work well on servers and reusing the same machinery on the desktop is not always appropriate.

    angel'o'sphere 11/08/04 05:28:31 AM EST

    I don't like the article.
    For several reasons I think they cheated and they coin old terms into new terms for no reason (except publicity). E.g. they mix up AOT with static compilation.
    AOT is an extension of JIT compilation, and not a compilation done ahead of the first execution.
    A VM based on a JIT compiler loads always only byte code and compiles the byte-code to native code on the fly depending on several algorithms/heuristics.
    A AOT compiler does JUST THE SAME on the first invocation of the byte code program, but it saves the generated native code to be available for later invocations of the same program. So for the later invocations, the compilation was ahead of time, not for the first one.
    The Excelsior JET is no AOT compiler but just a static compiler. However they seem to jump on the bandwagon of a new buzzword, because the term AOT is only used in academic circles currently (besides that Java 5.0 tries to cash compile informations and even native code over invocations).
    The next flaw is this: they measure a GUI application over only 600 "loops". As the exact form of the loop is not published, I have the impression they made the loop in a way that a "standard" HotSpot JIT does predictable not even attempt to compile much of the covered code.
    To understand that you have to know how a HotSpot JIT works. Two "big" strategies are used: fiddling with loops, this is a short code fragment, inside of one method, consider it as a for loop or while loop. You can do different things with it ... not interesting here.
    The second big thing is call stack sampling. Suppose you have very often the method calls A, B, C on the call stack, the VM decides to check if anything can be inlined or if any of those methods is jitted.
    In the "benchmark" of the article, you neither have a loop (that one is in the external driver program hidden) nor stack samples which occur often enough to cause a JIT compilation.
    Excellent literature about JIT compilation and strategies can be found here: http://www.research.ibm.com/jalapeno/publication.h tml and here: http://www-124.ibm.com/developerworks/oss/jikesrvm /info/papers.shtml
    IMHO: the Excelsior people tricked the HotSpot/JIT VMs in not doing their job, and thus you see the big performance gain. There are other tricks thinkable, e.g. not using the standard SWING library but a tweaked one, just remove some "synchronized" keywords if you are sure the benchmark does not need them, and voila ...

    Seun Osewa 11/07/04 02:32:53 PM EST

    combining the two approaches will lead to overhead similar to a JIT approach (hence, there's nothing to be gained for a long-running program)

    RAMMS+EIN 11/06/04 05:40:50 AM EST

    Why compare JIT against AOT? Why not have both?

    AOT compilation makes for fast start up time and fast run time. JIT advocates claim that it can lead to better performance, as more optimizations can be performed with run-time information. So why not combine the two? Compile it before the first run, and further optimize it at run-time where appropriate. That way, you get the best of both worlds.

    @ThingsExpo Stories
    The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportuni...
    19th Cloud Expo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Meanwhile, 94% of enterpri...
    Personalization has long been the holy grail of marketing. Simply stated, communicate the most relevant offer to the right person and you will increase sales. To achieve this, you must understand the individual. Consequently, digital marketers developed many ways to gather and leverage customer information to deliver targeted experiences. In his session at @ThingsExpo, Lou Casal, Founder and Principal Consultant at Practicala, discussed how the Internet of Things (IoT) has accelerated our abil...
    With so much going on in this space you could be forgiven for thinking you were always working with yesterday’s technologies. So much change, so quickly. What do you do if you have to build a solution from the ground up that is expected to live in the field for at least 5-10 years? This is the challenge we faced when we looked to refresh our existing 10-year-old custom hardware stack to measure the fullness of trash cans and compactors.
    The emerging Internet of Everything creates tremendous new opportunities for customer engagement and business model innovation. However, enterprises must overcome a number of critical challenges to bring these new solutions to market. In his session at @ThingsExpo, Michael Martin, CTO/CIO at nfrastructure, outlined these key challenges and recommended approaches for overcoming them to achieve speed and agility in the design, development and implementation of Internet of Everything solutions wi...
    DevOps at Cloud Expo, taking place Nov 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long dev...
    Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is expected in the amount of information being processed, managed, analyzed, and acted upon by enterprise IT. This amazing is not part of some distant future - it is happening today. One report shows a 650% increase in enterprise data by 2020. Other estimates are even higher....
    I wanted to gather all of my Internet of Things (IOT) blogs into a single blog (that I could later use with my University of San Francisco (USF) Big Data “MBA” course). However as I started to pull these blogs together, I realized that my IOT discussion lacked a vision; it lacked an end point towards which an organization could drive their IOT envisioning, proof of value, app dev, data engineering and data science efforts. And I think that the IOT end point is really quite simple…
    Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more business becomes digital the more stakeholders are interested in this data including how it relates to business. Some of these people have never used a monitoring tool before. They have a question on their mind like “How is my application doing” but no id...
    Identity is in everything and customers are looking to their providers to ensure the security of their identities, transactions and data. With the increased reliance on cloud-based services, service providers must build security and trust into their offerings, adding value to customers and improving the user experience. Making identity, security and privacy easy for customers provides a unique advantage over the competition.
    Is the ongoing quest for agility in the data center forcing you to evaluate how to be a part of infrastructure automation efforts? As organizations evolve toward bimodal IT operations, they are embracing new service delivery models and leveraging virtualization to increase infrastructure agility. Therefore, the network must evolve in parallel to become equally agile. Read this essential piece of Gartner research for recommendations on achieving greater agility.
    Smart Cities are here to stay, but for their promise to be delivered, the data they produce must not be put in new siloes. In his session at @ThingsExpo, Mathias Herberts, Co-founder and CTO of Cityzen Data, will deep dive into best practices that will ensure a successful smart city journey.
    Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - comp...
    SYS-CON Events announced today that Venafi, the Immune System for the Internet™ and the leading provider of Next Generation Trust Protection, will exhibit at @DevOpsSummit at 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Venafi is the Immune System for the Internet™ that protects the foundation of all cybersecurity – cryptographic keys and digital certificates – so they can’t be misused by bad guys in attacks...
    SYS-CON Events announced today Telecom Reseller has been named “Media Sponsor” of SYS-CON's 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.
    For basic one-to-one voice or video calling solutions, WebRTC has proven to be a very powerful technology. Although WebRTC’s core functionality is to provide secure, real-time p2p media streaming, leveraging native platform features and server-side components brings up new communication capabilities for web and native mobile applications, allowing for advanced multi-user use cases such as video broadcasting, conferencing, and media recording.
    Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at Cloud Expo, Ed Featherston, a director and senior enterprise architect at Collaborative Consulting, will discuss the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
    Pulzze Systems was happy to participate in such a premier event and thankful to be receiving the winning investment and global network support from G-Startup Worldwide. It is an exciting time for Pulzze to showcase the effectiveness of innovative technologies and enable them to make the world smarter and better. The reputable contest is held to identify promising startups around the globe that are assured to change the world through their innovative products and disruptive technologies. There w...
    Akana has announced the availability of version 8 of its API Management solution. The Akana Platform provides an end-to-end API Management solution for designing, implementing, securing, managing, monitoring, and publishing APIs. It is available as a SaaS platform, on-premises, and as a hybrid deployment. Version 8 introduces a lot of new functionality, all aimed at offering customers the richest API Management capabilities in a way that is easier than ever for API and app developers to use.
    SYS-CON Events announced today that 910Telecom will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Housed in the classic Denver Gas & Electric Building, 910 15th St., 910Telecom is a carrier-neutral telecom hotel located in the heart of Denver. Adjacent to CenturyLink, AT&T, and Denver Main, 910Telecom offers connectivity to all major carriers, Internet service providers, Internet backbones and ...