The default value is 50 percent. The following example shows how to set the percentage of the maximum amount of memory used for the Java heap for small heaps:. Sets the maximum tenuring threshold for use in adaptive GC sizing. The largest value is The default value is 15 for the parallel throughput collector, and 6 for the CMS collector. Sets the minimum allowed percentage of free heap space 0 to after a GC event.
If free heap space falls below this value, then the heap is expanded. Try different values for these parameters until they're as low as possible, yet still retain acceptable performance. Sets the minimum size in bytes of the memory allocation pool. The following examples show how to set the mimimum size of allocated memory to 6 MB using various units:.
Sets the ratio between young and old generation sizes. By default, this option is set to 2. The following example shows how to set the young-to-old ratio to Sets the initial size in bytes of the heap for the young generation nursery.
If the size for the young generation is too low, then a large number of minor GCs are performed. If the size is too high, then only full GCs are performed, which can take a long time to complete. The following examples show how to set the initial size of the young generation to MB using various units:. Sets the number of the stop-the-world STW worker threads. Sets the amount of time in milliseconds a softly reachable object is kept active on the heap after the last time it was referenced.
The default value is one second of lifetime per free megabyte in the heap. This difference means that the Client VM tends to flush soft references rather than grow the heap, whereas the Server VM tends to grow the heap rather than flush soft references. In the latter case, the value of the -Xmx option has a significant effect on how quickly soft references are garbage collected.
This option is enabled by default. If disabled, then it immediately reduces the Java heap to the target size instead of requiring multiple garbage collection cycles. Disable this option if you want to minimize the Java heap size.
You will likely encounter performance degradation when this option is disabled. See Performance Tuning Examples for a description of using the MaxHeapFreeRatio option to keep the Java heap small by reducing the dynamic footprint for embedded applications. Identifies String objects reaching the specified age that are considered candidates for deduplication. An object's age is a measure of how many times it has survived garbage collection.
This is sometimes referred to as tenuring. Note: String objects that are promoted to an old heap region before this age has been reached are always considered candidates for deduplication. The default value for this option is 3.
Sets the ratio between eden space size and survivor space size. By default, this option is set to 8. Sets the desired percentage of survivor space 0 to used after young garbage collection. Sets the initial size in bytes of a thread-local allocation buffer TLAB.
If this option is set to 0, then the JVM selects the initial size automatically. Enables the use of the parallel scavenge garbage collector also known as the throughput collector to improve the performance of your application by leveraging multiple processors. By default, this option is disabled and the default collector is used. Enables string deduplication. By default, this option is disabled.
To use this option, you must enable the garbage-first G1 garbage collector. String deduplication reduces the memory footprint of String objects on the Java heap by taking advantage of the fact that many String objects are identical. Instead of each String object pointing to its own character array, identical String objects can point to and share the same character array. Enables the use of the Z garbage collector. This garbage collector is best for providing lowest latency with large Java heaps at some throughput cost.
These java options are deprecated and might be removed in a future JDK release. They're still accepted and acted upon, but a warning is issued when they're used.
Sets the file to which verbose GC events information should be redirected for logging. The -Xloggc option overrides -verbose:gc if both are given with the same java command. Sets the initial amount of memory that the JVM may use for the Java heap before applying ergonomics heuristics as a ratio of the maximum amount determined as described in the -XX:MaxRAM option.
The default value is Sets the maximum amount of memory that the JVM may use for the Java heap before applying ergonomics heuristics as a fraction of the maximum amount determined as described in the -XX:MaxRAM option. The default value is 4. Sets the maximum amount of memory that the JVM may use for the Java heap before applying ergonomics heuristics as a fraction of the maximum amount determined as described in the -XX:MaxRAM option for small heaps.
The default value is 2. Enables tracing of classes as they are loaded. By default, this option is disabled and classes aren't traced. Enables tracing of all loaded classes in the order in which they're referenced.
Enables tracing of constant pool resolutions. By default, this option is disabled and constant pool resolutions aren't traced. Enables tracing of the loader constraints recording. By default, this option is disabled and loader constraints recording isn't traced. These java options are still accepted but ignored, and a warning is issued when they're used.
These java options have been removed in JDK 13 and using them results in an error of:. For the lists and descriptions of options removed in previous releases see the Removed Java Options section in:. You can shorten or simplify the java command by using argument files to specify one or more text files that contain arguments, such as options and class names, which are passed to the java command. This let's you to create java commands of any length on any operating system. In the command line, use the at sign prefix to identify an argument file that contains java options and class names.
When the java command encounters a file beginning with the at sign , it expands the contents of that file into an argument list just as they would be specified on the command line. The java launcher expands the argument file contents until it encounters the --disable- files option. You can use the --disable- files option anywhere on the command line, including in an argument file, to stop argument files expansion. Any option that contains spaces, such as a path component, must be within quotation marks using quotation '"' characters in its entirety.
File names in an argument file are relative to the current directory, not to the location of the argument file. Use the number sign in the argument file to identify comments. All characters following the are ignored until the end of line. Additional at sign prefixes to prefixed options act as an escape, the first is removed and the rest of the arguments are presented to the launcher literally.
The two lines are concatenated with the leading white spaces trimmed. To prevent trimming the?? You can use a single argument file, such as myargumentfile in the following example, to hold all required java arguments:.
You can include relative paths in argument files; however, they're relative to the current working directory and not to the paths of the argument files themselves. Any relative paths that they contain are relative to the current working directory and not to the argument files:. There are occasions when having insight into the current state of the JVM code heap would be helpful to answer questions such as:. To provide this insight, a code heap state analytics feature has been implemented that enables on-the-fly analysis of the code heap.
The analytics process is divided into two parts. The first part examines the entire code heap and aggregates all information that is believed to be useful or important.
The second part consists of several independent steps that print the collected information with an emphasis on different aspects of the data. Data collection and printing are done on an "on request" basis. If you are only interested in how the code heap looks like after running a sample workload, you can use the command line option:. To see the code heap state when a "CodeCache full" condition exists, start the VM with the command line option:.
See CodeHeap State Analytics OpenJDK for a detailed description of the code heap state analytics feature, the supported functions, and the granularity options. GC logging for the JVM has been changed to use the new logging framework. In addition, runtime logging has also been changed to use the JVM unified logging framework. The mapping of legacy runtime logging flags to the corresponding new Xlog configuration is described in Convert Runtime Logging Flags to Xlog. Applies multiple arguments in the order that they appear on the command line.
Multiple -Xlog arguments for the same output override each other in their given order. Omitting the tag-selection defaults to a tag-set of all and a level of info. The all tag is a meta tag consisting of all tag-sets available.
Matching with a wildcard selects all tag sets that contain at least the specified tags. Without the wildcard, only exact matches of the specified tag sets are selected. When the -Xlog option and nothing else is specified on the command line, the default configuration is used. The default configuration logs all messages with a level that matches either warning or error regardless of what tags the message is associated with.
The default configuration is equivalent to entering the following on the command line:. Logging can also be controlled at run time through Diagnostic Commands with the jcmd utility. Everything that can be specified on the command line can also be specified dynamically with the VM. As the diagnostic commands are automatically exposed as MBeans, you can use JMX to change logging configuration at run time.
Each log message has a level and a tag set associated with it. The level of the message corresponds to its details, and the tag set corresponds to what the message contains or which JVM component it involves such as, gc , jit , or os.
Mapping legacy runtime logging flags to the corresponding Xlog configuration is described in Convert Runtime Logging Flags to Xlog. There are literally dozens of log tags, which in the right combinations, will enable a range of logging output.
The full set of available log tags can be seen using -Xlog:help. Specifying all instead of a tag combination matches all tag combinations. You can also configure text files to handle file rotation based on file size and a number of files to rotate. The target size of the files isn't guaranteed to be exact, it's just an approximate value. Files are rotated by default with up to 5 rotated files of target size 20 MB, unless configured otherwise.
There's a possibility of the pre-existing log file getting overwritten. Logging messages are decorated with information about the message. You can configure each output to use a custom set of decorators. The order of the output is always the same as listed in the table. You can configure the decorations to be used at run time.
Decorations are prepended to the log message. For example:. Omitting decorators defaults to uptime , level , and tags. The none decorator is special and is used to turn off all decorations. Logs all messages by using the info level to stdout with uptime , levels , and tags decorations. This is equivalent to using:. Logs messages tagged with the gc tag using the trace level to a rotating file set with 5 files with size 1 MB with the base name gctrace.
The default configuration for all other messages at level warning is still in effect. You use values provided to all Java Virtual Machine JVM command-line flags for validation and, if the input value is invalid or out-of-range, then an appropriate error message is displayed.
Whether they're set ergonomically, in a command line, by an input tool, or through the APIs for example, classes contained in the package java. Range and constraints are validated either when all flags have their values set during JVM initialization or a flag's value is changed during runtime for example using the jcmd tool. The JVM is terminated if a value violates either the range or constraint check and an appropriate error message is printed on the error stream.
This flag allows automatic testing of the flags by the values provided by the ranges. For the flags that have the ranges specified, the type, name, and the actual range is printed in the output.
For the flags that don't have the range specified, the values aren't displayed in the print out. This helps to identify the flags that need to be implemented. The automatic testing framework can skip those flags that don't have values and aren't implemented.
You use large pages, also known as huge pages, as memory pages that are significantly larger than the standard memory page size which varies depending on the processor and operating system. Large pages optimize processor Translation-Lookaside Buffers. A Translation-Lookaside Buffer TLB is a page translation cache that holds the most-recently used virtual-to-physical address translations. A TLB is a scarce system resource. A TLB miss can be costly because the processor must then read from the hierarchical page table, which may require multiple memory accesses.
By using a larger memory page size, a single TLB entry can represent a larger memory range. This results in less pressure on a TLB, and memory-intensive applications may have better performance. However, large pages page memory can negatively affect system performance. For example, when a large mount of memory is pinned by an application, it may create a shortage of regular memory and cause excessive paging in other applications and slow down the entire system. Also, a system that has been up for a long time could produce excessive fragmentation, which could make it impossible to reserve enough large page memory.
No additional configuration is necessary. The 2. Some vendors have backported the code to their 2. To check if your system can support large page memory, try the following:. If the output shows the three "Huge" variables, then your system can support large page memory but it needs to be configured. If the command prints nothing, then your system doesn't support large pages. To configure the system to use large page memory, login as root , and then follow these steps:.
It must be larger than the Java heap size. These steps can allocate large pages for the following areas:. To use large pages support on Windows, the administrator must first assign additional privileges to the user who is running the application:.
Note that these steps are required even if it's the administrator who's running the application, because administrators by default don't have the privilege to lock pages in memory. Archiving application classes provides better start up time at runtime.
Prior to JDK 11, a non-empty directory was reported as a fatal error in the following conditions:. A non-empty directory is reported as a fatal error in the following conditions:. When an array in the class list is encountered, CDS dump time gives the explicit error message:. Anyway, I am away from having a Windows machine available to test on. I will try again in the AM and see if I can make this work right. Exception in thread "Thread-1" org. SWTException: Invalid thread access at org.
If it works, you might need to do more clever configuring so other platforms don't pass teh - XstartOnFirstThread param. I also added the dev library to surefire's classpath.
Here is the relevant part of my pom:. It looks like its looking in the wrong folder for the. Reply to author. Report message as abuse. Connect and share knowledge within a single location that is structured and easy to search. What does it mean? It seems to be that some process wants thread 0. Is this correct? Please note: I have a run method in my main class. It doesn't seem to be overriding anything and I'm not implementing runnable. The option causes the JVM to use thread 0 to start the application.
How are we doing? Please help us improve Stack Overflow. Take our short survey. View code. Window ; import static de. Caused by: java. IllegalStateException: GLFW windows may only be created on the main thread and that thread must be the first thread in the process. For offscreen rendering, make sure another window toolkit e.
Soon after that, the main game loop will start. About No description, website, or topics provided. Releases No releases published.
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