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JDK Flight Recorder
JDK Flight Recorder is an event recorder built into the OpenJDK Java virtual machine. It can be thought of as the software equivalent of a Data Flight Recorder (Black Box) in a commercial aircraft. It captures information about the JVM itself, and the application running in the JVM. There is a wide variety of data captured, for example method profiling, allocation profiling and garbage collection related events. The JDK Flight Recorder was designed to minimize the Observer Effect in the profiled system, and is meant to be always on in production systems. The technology was open sourced in 2018. Analysis and visualization of flight recordings are normally done using JDK Mission Control. Technology A recording file consists of binary chunks of data. Each chunk is self describing and self contained. In other words, the metadata (such as the datatype and the content type of each attribute) needed to make use of the data (not only parse the events, but actually use them) is included i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Java Virtual Machine
A Java virtual machine (JVM) is a virtual machine that enables a computer to run Java programs as well as programs written in other languages that are also compiled to Java bytecode. The JVM is detailed by a specification that formally describes what is required in a JVM implementation. Having a specification ensures interoperability of Java programs across different implementations so that program authors using the Java Development Kit (JDK) need not worry about idiosyncrasies of the underlying hardware platform. The JVM reference implementation is developed by the OpenJDK project as open source code and includes a JIT compiler called HotSpot. The commercially supported Java releases available from Oracle are based on the OpenJDK runtime. Eclipse OpenJ9 is another open source JVM for OpenJDK. JVM specification The Java virtual machine is an abstract (virtual) computer defined by a specification. It is a part of java runtime environment. The garbage-collection algorit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Observer Effect (information Technology)
In information technology, the observer effect is the impact on the behaviour of a computer process caused by the act of observing the process while it is running. For example: if a process uses a log file to record its progress, the process could slow down. Furthermore, the act of viewing the file while the process is running could cause an I/O error in the process, which could, in turn, cause it to stop. Another example would be observing the performance of a CPU by running both the observed and observing programs on the same CPU, which will lead to inaccurate results because the observer program itself affects the CPU performance (modern, heavily cached and pipelined CPUs are particularly affected by this kind of observation). The observer effect could either have a positive or negative impact on the computer process behaviour. A positive impact can be software bugs, also known as Heisenbugs, which diminish or change their negative behavior when observation mechanisms, such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
JDK Mission Control
JDK Mission Control is an open source tools suite for the Java virtual machine. The tools help finding problems in, and optimizing, programs running on the JVM in production. JDK Mission Control supports OpenJDK 11 (and above) and Oracle JDK 7u40 (and above). JDK Mission Control primarily consists of the following tools: * A JFR ( JDK Flight Recorder) analyzer and visualizer * A JMX Console There are also various plug-ins available, such as: * A heap dump (hprof format) analyzer (JOverflow) History JDK Mission Control started out as JRockit Mission Control, a production time profiling and diagnostics tools suite which was delivered as a part of the JRockit JVM distribution. After Oracle acquired Sun Microsystems, JRockit Flight Recorder and JRockit Mission Control were rebranded Java Flight Recorder and Java Mission Control. In 2018 both Java Flight Recorder and Java Mission Control were open sourced. When open sourced they were rebranded JDK Mission Control and JDK Flight Rec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time Stamp Counter
The Time Stamp Counter (TSC) is a 64-bit register present on all x86 processors since the Pentium. It counts the number of CPU cycles since its reset. The instruction RDTSC returns the TSC in EDX:EAX. In x86-64 mode, RDTSC also clears the upper 32 bits of RAX and RDX. Its opcode is 0F 31. Pentium competitors such as the Cyrix 6x86 did not always have a TSC and may consider RDTSC an illegal instruction. Cyrix included a Time Stamp Counter in their MII. Use The Time Stamp Counter was once an excellent high-resolution, low-overhead way for a program to get CPU timing information. With the advent of multi-core/hyper-threaded CPUs, systems with multiple CPUs, and hibernating operating systems, the TSC cannot be relied upon to provide accurate results — unless great care is taken to correct the possible flaws: rate of tick and whether all cores (processors) have identical values in their time-keeping registers. There is no promise that the timestamp counters of multiple CPUs on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
JSON
JSON (JavaScript Object Notation, pronounced ; also ) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other serializable values). It is a common data format with diverse uses in electronic data interchange, including that of web applications with servers. JSON is a language-independent data format. It was derived from JavaScript, but many modern programming languages include code to generate and parse JSON-format data. JSON filenames use the extension .json. Any valid JSON file is a valid JavaScript (.js) file, even though it makes no changes to a web page on its own. Douglas Crockford originally specified the JSON format in the early 2000s. He and Chip Morningstar sent the first JSON message in April 2001. Naming and pronunciation The 2017 international standard (ECMA-404 and ISO/IEC 21778:2017) specifies "Pronounced , as in ' Jaso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Java Platform
Java is a set of computer software and specifications developed by James Gosling at Sun Microsystems, which was later acquired by the Oracle Corporation, that provides a system for developing application software and deploying it in a cross-platform computing environment. Java is used in a wide variety of computing platforms from embedded devices and mobile phones to enterprise servers and supercomputers. Java applets, which are less common than standalone Java applications, were commonly run in secure, sandboxed environments to provide many features of native applications through being embedded in HTML pages. Writing in the Java programming language is the primary way to produce code that will be deployed as byte code in a Java virtual machine (JVM); byte code compilers are also available for other languages, including Ada, JavaScript, Python, and Ruby. In addition, several languages have been designed to run natively on the JVM, including Clojure, Groovy, and S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Java Version History
The Java language has undergone several changes since JDK 1.0 as well as numerous additions of classes and packages to the standard library. Since J2SE 1.4, the evolution of the Java language has been governed by the Java Community Process (JCP), which uses ''Java Specification Requests'' (JSRs) to propose and specify additions and changes to the Java platform. The language is specified by the ''Java Language Specification'' (JLS); changes to the JLS are managed undeJSR 901 In September 2017, Mark Reinhold, chief Architect of the Java Platform, proposed to change the release train to "one feature release every six months" rather than the then-current two-year schedule. This proposal took effect for all following versions, and is still the current release schedule. In addition to the language changes, other changes have been made to the Java Class Library over the years, which has grown from a few hundred classes in JDK 1.0 to over three thousand in J2SE&n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
JRockit
JRockit was a proprietary Java virtual machine (JVM) originally developed by Appeal Virtual Machines, acquired by BEA Systems in 2002, and became part of Oracle Fusion Middleware as part of acquisition of BEA Systems in 2008. The JRockit code base was discontinued by Oracle, with some features being integrated into the HotSpot virtual machine as part of the mainline development of the Java platform. JRockit only ever supported Java 6, which is now considered an obsolete release. History Following the finalization of the acquisition of Sun Microsystems, Oracle announced in JavaOne 2010 that the best features of JRockit would be implemented in OpenJDK. In May 2011, Oracle announced that JRockit has become free, and confirmed the plan to port JRockit features on OpenJDK OpenJDK (Open Java Development Kit) is a free and open-source implementation of the Java Platform, Standard Edition (Java SE). It is the result of an effort Sun Microsystems began in 2006. The implementation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Java (programming Language) Software
Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's most populous island, home to approximately 56% of the Indonesian population. Indonesia's capital city, Jakarta, is on Java's northwestern coast. Many of the best known events in Indonesian history took place on Java. It was the centre of powerful Hindu-Buddhist empires, the Islamic sultanates, and the core of the colonial Dutch East Indies. Java was also the center of the Indonesian struggle for independence during the 1930s and 1940s. Java dominates Indonesia politically, economically and culturally. Four of Indonesia's eight UNESCO world heritage sites are located in Java: Ujung Kulon National Park, Borobudur Temple, Prambanan Temple, and Sangiran Early Man Site. Formed by volcanic eruptions due to geologic subduction of the Australi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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