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What command-line options does the Java HotSpot VM provide
« on: October 25, 2008, 02:49:55 PM »
Categories of Java HotSpot VM Options
 
Standard options recognized by the Java HotSpot VM are described on the Java Application Launcher reference pages for Windows, Solaris and Linux. This document deals exclusively with non-standard options recognized by the Java HotSpot VM:

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.
Options that are specified with -XX are not stable and are not recommended for casual use. These options are subject to change without notice.
 
Some Useful -XX Options
 
Default values are listed for Java SE 6 for Solaris Sparc with -server. Some options may vary per architecture/OS/JVM version. Platforms with a differing default value are listed in the description.

Boolean options are turned on with -XX:+<option> and turned off with -XX:-<option>.
Numeric options are set with -XX:<option>=<number>. 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).
String options are set with -XX:<option>=<string>, are usually used to specify a file, a path, or a list of commands
Flags marked as manageable are dynamically writeable through the JDK management interface (com.sun.management.HotSpotDiagnosticMXBean API) and also through JConsole. In Monitoring and Managing Java SE 6 Platform Applications, Figure 3 shows an example. The manageable flags can also be set through jinfo -flag.

The options below are loosely grouped into three categories.

Behavioral options change the basic behavior of the VM.
Performance tuning options are knobs which can be used to tune VM performance.
Debugging options generally enable tracing, printing, or output of VM information.
 
Behavioral Options

Option and Default Value
Description
-XX:-AllowUserSignalHandlers   Do not complain if the application installs signal handlers. (Relevant to Solaris and Linux only.)

-XX:AltStackSize=16384   Alternate signal stack size (in Kbytes). (Relevant to Solaris only, removed from 5.0.)

-XX:-DisableExplicitGC   Disable calls to System.gc(), JVM still performs garbage collection when necessary.

-XX:+FailOverToOldVerifier   Fail over to old verifier when the new type checker fails. (Introduced in 6.)

-XX:+HandlePromotionFailure   The youngest generation collection does not require a guarantee of full promotion of all live objects. (Introduced in 1.4.2 update 11) [5.0 and earlier: false.]

-XX:+MaxFDLimit   Bump the number of file descriptors to max. (Relevant  to Solaris only.)

-XX:PreBlockSpin=10   Spin count variable for use with -XX:+UseSpinning. Controls the maximum spin iterations allowed before entering operating system thread synchronization code. (Introduced in 1.4.2.)

-XX:-RelaxAccessControlCheck   Relax the access control checks in the verifier. (Introduced in 6.)

-XX:+ScavengeBeforeFullGC   Do young generation GC prior to a full GC. (Introduced in 1.4.1.)

-XX:+UseAltSigs   Use alternate signals instead of SIGUSR1 and SIGUSR2 for VM internal signals. (Introduced in 1.3.1 update 9, 1.4.1. Relevant to Solaris only.)

-XX:+UseBoundThreads   Bind user level threads to kernel threads. (Relevant to Solaris only.)

-XX:-UseConcMarkSweepGC   Use concurrent mark-sweep collection for the old generation. (Introduced in 1.4.1)

-XX:+UseGCOverheadLimit   Use a policy that limits the proportion of the VM\'s time that is spent in GC before an OutOfMemory error is thrown. (Introduced in 6.)

-XX:+UseLWPSynchronization   Use LWP-based instead of thread based synchronization. (Introduced in 1.4.0. Relevant to Solaris only.)

-XX:-UseParallelGC   Use parallel garbage collection for scavenges. (Introduced in 1.4.1)

-XX:-UseParallelOldGC   Use parallel garbage collection for the full collections. Enabling this option automatically sets -XX:+UseParallelGC. (Introduced in 5.0 update 6.)

-XX:-UseSerialGC   Use serial garbage collection. (Introduced in 5.0.)

-XX:-UseSpinning   Enable naive spinning on Java monitor before entering operating system thread synchronizaton code. (Relevant to 1.4.2 and 5.0 only.) [1.4.2, multi-processor Windows platforms: true]

-XX:+UseTLAB   Use thread-local object allocation (Introduced in 1.4.0, known as UseTLE prior to that.) [1.4.2 and earlier, x86 or with -client: false]

-XX:+UseSplitVerifier   Use the new type checker with StackMapTable attributes. (Introduced in 5.0.)[5.0: false]

-XX:+UseThreadPriorities   Use native thread priorities.

-XX:+UseVMInterruptibleIO   Thread interrupt before or with EINTR for I/O operations results in OS_INTRPT. (Introduced in 6. Relevant to Solaris only.)


Back to Options
 
Performance Options

Option and Default Value
Description
-XX:+AggressiveOpts   Turn on point performance compiler optimizations that are expected to be default in upcoming releases. (Introduced in 5.0 update 6.)

-XX:CompileThreshold=10000   Number of method invocations/branches before compiling [-client: 1,500]

-XX:LargePageSizeInBytes=4m   Sets the large page size used for the Java heap. (Introduced in 1.4.0 update 1.) [amd64: 2m.]

-XX:MaxHeapFreeRatio=70   Maximum percentage of heap free after GC to avoid shrinking.

-XX:MaxNewSize=size   Maximum size of new generation (in bytes). Since 1.4, MaxNewSize is computed as a function of NewRatio. [1.3.1 Sparc: 32m; 1.3.1 x86: 2.5m.]

-XX:MaxPermSize=64m   Size of the Permanent Generation.  [5.0 and newer: 64 bit VMs are scaled 30% larger; 1.4 amd64: 96m; 1.3.1 -client: 32m.]

-XX:MinHeapFreeRatio=40   Minimum percentage of heap free after GC to avoid expansion.

-XX:NewRatio=2   Ratio of new/old generation sizes. [Sparc -client: 8; x86 -server: 8; x86 -client: 12.]-client: 4 (1.3) 8 (1.3.1+), x86: 12]

-XX:NewSize=2.125m   Default size of new generation (in bytes) [5.0 and newer: 64 bit VMs are scaled 30% larger; x86: 1m; x86, 5.0 and older: 640k]

-XX:ReservedCodeCacheSize=32m   Reserved code cache size (in bytes) - maximum code cache size. [Solaris 64-bit, amd64, and -server x86: 48m; in 1.5.0_06 and earlier, Solaris 64-bit and and64: 1024m.]

-XX:SurvivorRatio=8   Ratio of eden/survivor space size [Solaris amd64: 6; Sparc in 1.3.1: 25; other Solaris platforms in 5.0 and earlier: 32]

-XX:TargetSurvivorRatio=50   Desired percentage of survivor space used after scavenge.

-XX:ThreadStackSize=512   Thread Stack Size (in Kbytes). (0 means use default stack size) [Sparc: 512; Solaris x86: 320 (was 256 prior in 5.0 and earlier); Sparc 64 bit: 1024; Linux amd64: 1024 (was 0 in 5.0 and earlier); all others 0.]

-XX:+UseBiasedLocking   Enable biased locking. For more details, see this tuning example. (Introduced in 5.0 update 6.) [5.0: false]

-XX:+UseFastAccessorMethods   Use optimized versions of Get<Primitive>Field.

-XX:-UseISM   Use Intimate Shared Memory. [Not accepted for non-Solaris platforms.] For details, see Intimate Shared Memory.

-XX:+UseLargePages   Use large page memory. (Introduced in 5.0 update 5.) For details, see Java Support for Large Memory Pages.

-XX:+UseMPSS   Use Multiple Page Size Support w/4mb pages for the heap. Do not use with ISM as this replaces the need for ISM. (Introduced in 1.4.0 update 1, Relevant to Solaris 9 and newer.) [1.4.1 and earlier: false]

-XX:+StringCache   Enables caching of commonly allocated strings.


Back to Options
 
Debugging Options

Option and Default Value
Description
-XX:-CITime   Prints time spent in JIT Compiler. (Introduced in 1.4.0.)

-XX:ErrorFile=./hs_err_pid<pid>.log   If an error occurs, save the error data to this file. (Introduced in 6.)

-XX:-ExtendedDTraceProbes   Enable performance-impacting dtrace probes. (Introduced in 6. Relevant to Solaris only.)

-XX:HeapDumpPath=./java_pid<pid>.hprof   Path to directory or filename for heap dump. Manageable. (Introduced in 1.4.2 update 12, 5.0 update 7.)

-XX:-HeapDumpOnOutOfMemoryError   Dump heap to file when java.lang.OutOfMemoryError is thrown. Manageable. (Introduced in 1.4.2 update 12, 5.0 update 7.)

-XX:OnError="<cmd args>;<cmd args>"   Run user-defined commands on fatal error. (Introduced in 1.4.2 update 9.)

-XX:OnOutOfMemoryError="<cmd args>;
<cmd args>"   Run user-defined commands when an OutOfMemoryError is first thrown. (Introduced in 1.4.2 update 12, 6)

-XX:-PrintClassHistogram   Print a histogram of class instances on Ctrl-Break. Manageable. (Introduced in 1.4.2.) The jmap -histo command provides equivalent functionality.

-XX:-PrintConcurrentLocks   Print java.util.concurrent locks in Ctrl-Break thread dump. Manageable. (Introduced in 6.) The jstack -l command provides equivalent functionality.

-XX:-PrintCommandLineFlags   Print flags that appeared on the command line. (Introduced in 5.0.)

-XX:-PrintCompilation   Print message when a method is compiled.

-XX:-PrintGC   Print messages at garbage collection. Manageable.

-XX:-PrintGCDetails   Print more details at garbage collection. Manageable. (Introduced in 1.4.0.)

-XX:-PrintGCTimeStamps   Print timestamps at garbage collection. Manageable (Introduced in 1.4.0.)

-XX:-PrintTenuringDistribution   Print tenuring age information.

-XX:-TraceClassLoading   Trace loading of classes.

-XX:-TraceClassLoadingPreorder   Trace all classes loaded in order referenced (not loaded). (Introduced in 1.4.2.)

-XX:-TraceClassResolution   Trace constant pool resolutions. (Introduced in 1.4.2.)

-XX:-TraceClassUnloading   Trace unloading of classes.

-XX:-TraceLoaderConstraints   Trace recording of loader constraints. (Introduced in 6.)

source:http://java.sun.com/javase/technologies/hotspot/vmoptions.jsp

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What command-line options does the Java HotSpot VM provide
« on: October 25, 2008, 02:49:55 PM »

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