Spin count variable for use with -XX:+UseSpinning. (Introduced in 1.4.2 update 11) īump the number of file descriptors to max. The youngest generation collection does not require a guarantee of full promotion of all live objects. Note that the JVM still performs garbage collection when necessary.įail over to old verifier when the new type checker fails. Use -XX:+DisableExplicitGC to disable calls to System.gc(). (Relevant to Solaris only, removed from 5.0.)īy default calls to System.gc() are enabled (-XX:-DisableExplicitGC).
(Relevant to Solaris and Linux only.)Īlternate signal stack size (in Kbytes). Debugging options generally enable tracing, printing, or output of VM information.ĭo not complain if the application installs signal handlers.Performance tuning options are knobs which can be used to tune VM performance.Garbage First (G1) Garbage Collection Options.
Behavioral options change the basic behavior of the VM. The options below are loosely grouped into categories. The manageable flags can also be set through jinfo -flag. In Monitoring and Managing Java SE 6 Platform Applications, Figure 3 shows an example. String options are set with -XX:=, are usually used to specify a file, a path, or a list of commandsįlags marked as manageable are dynamically writeable through the JDK management interface ( API) and also through JConsole. Numbers can include 'm' or 'M' for megabytes, 'k' or 'K' for kilobytes, and 'g' or 'G' for gigabytes (for example, 32k is the same as 32768). Boolean options are turned on with -XX:+ and turned off with -XX:-.Disa. Platforms with a differing default value are listed in the description. Some options may vary per architecture/OS/JVM version. Some Useful -XX Optionsĭefault values are listed for Java SE 6 for Solaris Sparc with -server. Users of JDKs older than 1.3.0 who wish to port to a Java HotSpot VM, should see Java HotSpot Equivalents of Exact VM flags. Options that are specified with -XX are not stable and are subject to change without notice. Options that begin with -X are non-standard (not guaranteed to be supported on all VM implementations), and are subject to change without notice in subsequent releases of the JDK. This document deals exclusively with non-standard options recognized by the Java HotSpot VM: Standard options recognized by the Java HotSpot VM are described on the Java Application Launcher reference pages for Windows and Solaris & Linux. Unless otherwise noted, all information in this document pertains to both the Java HotSpot Client VM and the Java HotSpot Server VM. This document provides information on typical command-line options and environment variables that can affect the performance characteristics of the Java HotSpot Virtual Machine. For JDK 8 please see the Windows, Solaris reference pages. Please note that this page only applies to JDK 7 and earlier releases.
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