A Collection of JVM Options

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A Collection of JVM Options compiled by: Joseph D. Mocker (Sun Microsystems, Inc.) revision: 13.Dec.2005

This document is a compilation of all the JVM options for various versions of the JVM on primarily SPARC/Solaris Platform. The descriptions for each option are taken mostly verbatim from the reference documents.

The JavaTM HotSpot VM Options page makes some good points regarding the different types of options, which should be followed when reading this document as well. To paraphrase:

• Standard options recognized by the Java HotSpot VM are described on the Java Application Launcher reference pages.



• 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 Java 2 SDK.



• Because the -XX options have specific system requirements for correct operation and may require privileged access to system configuration parameters, they are not recommended for casual use. These options are also subject to change without notice.
  

Please submit any comments, corrections, additions to jvm-options-list@sun.com.

Caveats: I am not associated with any Java Platform development group, I simply put this list together from the various reference sources I could find and without referring to any source code. I have done my best to ensure the options are valid for representative JVMs, however I have not tested every version of every JVM so it is quite possible that options may not be valid in all cases.

Option Type 1.3.1 1.4.0 1.4.1 1.4.2 1.5.0 Description -client bool Y Y Y Y Y Use Client HotSpot VM. Must be first option. -server bool Y Y Y Y Y Use Server HotSpot VM. Must be first option. -verbose[:class|gc|jni] bool Y Y Y Y Y enable output of various pieces of the VM. specifying options twice may produce more detailed output. -cp path Y Y Y Y Y set search path for application classes and resources -classpath path Y Y Y Y Y set search path for application classes and resources -version bool Y Y Y Y Y print product version and exit -showversion bool Y Y Y Y Y print product version and continue -fullversion bool Y Y Y Y Y print full java version and exit -d32 bool   Y Y Y Y use a 32-bit data model if available -d64 bool   Y Y Y Y use a 64-bit data model if available -ea[:packagename...|:classname] list   Y Y Y Y enable assertions -enableassertions[:packagename...|:classname] list   Y Y Y Y enable assertions -da[:packagename...|:classname] list   Y Y Y Y disable assertions -disableassertions[:packagename...|:classname] list   Y Y Y Y disable assertions -esa bool   Y Y Y Y enable system assertions -enablesystemassertions bool   Y Y Y Y enable system assertions -dsa bool   Y Y Y Y disable system assertions -disablesystemassertions bool   Y Y Y Y disable system assertions -Dname=value nv Y Y Y Y Y set a system property -jre-restrict-search bool         Y include user private JREs in the version search -jre-no-restrict-search bool         Y exclude user private JREs in the version search -Xt bool O O O O O turn on instruction tracing -Xtm bool O O O O O turn on method tracing -Xbootclasspath[/a|/p]:<path> list Y Y Y Y Y set, append to, or prepend to boot class path -Xdebug bool Y Y Y Y Y enable remote debugging -Xfuture bool Y Y Y Y Y enable strictest checks, anticipating future default -Xcheck:jni bool Y Y Y Y Y perform additional checks for JNI functions -Xnoclassgc bool Y Y Y Y Y disable class garbage collection -Xss<size> size Y Y Y Y Y set maximum native stack size for any thread -Xoss<size> size Y Y Y Y Y set maximum Java stack size for any thread. Note: This option is useless with HotSpot as HotSpot doesn't have separate native and Java stacks. -Xms<size> size Y Y Y Y Y set initial Java heap size -Xmx<size> size Y Y Y Y Y set maximum Java heap size -Xmn<size> size   Y Y Y Y Size of young generation -Xrs bool Y Y Y Y Y reduce the use of OS signals -Xrunhprof[:help]|[:option=value, ...] list Y Y   Y Y perform heap or cpu profiling -Xmaxjitcodesize<size> size Y Y Y Y Y set the maximum size (in bytes) for the JIT code area -Xsqnopause bool Y Y Y Y Y do not pause for user interaction on SIGQUIT -Xoptimize bool Y Y Y Y Y Use optimizing JIT compiler (SPARC only). Replaced by -server in later VMs -Xmixed bool Y Y Y Y Y mixed mode execution (default) -Xint bool Y Y Y Y Y interpreted mode execution only -Xincgc bool Y Y Y Y Y Incremental GC -Xconcgc bool     Y Y Y Concurrent GC. Replaced by -XX:+UseConcMarkSweepGC (available beginning with J2SE 1.4.1) -Xprof bool Y Y Y Y Y Precursor to -Xrunprof. -Xaprof path Y Y Y Y Y Simple allocation profiler. unstable. debug only. -Xloggc:<file> path   Y Y Y Y Log garbage collection actions to a specified file. -Xcomp bool Y Y Y Y Y Forces HotSpot to compile 100% of the code with maximum optimization. -Xbatch bool Y Y Y Y Y Forces HotSpot to compile methods in the foreground. Normally method compilation is moved from the foreground to a background process if they take long. This allows allows the interpreted version to continue to run until the compiled version is complete. This option prevents background compiling. -Xconcurrentio bool Y Y Y Y Y The main feature turned on with -Xconcurrentio is to use LWP based synchronization instead of thread based synchronization. We have found certain applications to speed up by over 40%. In 1.4, LWP based synchronization is the default, but -Xconcurrentio can still help since it turns on some other internal options. -Xgenconfig bool           1.2 option only -Xverifyheap bool O O O O O Verify heap integrity. Replaced by -XX:+VerifyBeforeGC -XX:+VerifyAfterGC -XX:+VerifyTLE (-XX:+VerifyTLAB in J2SE 1.4) -XX:+VerifyBeforeScavenge -XX:+VerifyAfterScavenge (all debug only) -XX:+PrintHeapUsageOverTime bool           Print heap usage and capacity with timestamps   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 -XX:+PrintInlining bool           Print message about inlined methods (debug only)   Java HotSpot VM Options -XX:+DontYieldALotInterval bool           Interval in milliseconds between yields. (debug only)   Java HotSpot VM Options -XX:+VerifyBeforeGC bool               Java HotSpot VM Options -XX:+VerifyAfterGC bool               Java HotSpot VM Options -XX:+VerifyTLE bool               Java HotSpot VM Options -XX:+VerifyTLAB bool       Y       Java HotSpot VM Options -XX:+VerifyBeforeScavenge bool               Java HotSpot VM Options -XX:+VerifyAfterScavenge bool               Java HotSpot VM Options -XX:+AggressiveHeap bool Y Y Y Y Y This option instructs the JVM to push memory use to the limit: the overall heap is more than 3850MB, the allocation area of each thread is 256K, the memory management policy defers collection as long as possible, and (beginning with J2SE 1.3.1_02) some GC activity is done in parallel.   Big Heaps and Intimate Shared Memory (ISM) Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine -XX:AdaptivePermSizeWeight=<value> uintx     Y Y Y   -XX:AdaptiveSizeDecrementScaleFactor=<value> uintx         Y   -XX:AdaptiveSizePolicyCollectionCostMargin=<value> uintx         Y   -XX:AdaptiveSizePolicyFootprintThreshold=<value> uintx         Y   -XX:AdaptiveSizePolicyInitializingSteps=<value> uintx         Y   -XX:AdaptiveSizePolicyWeight=<value> uintx     Y Y Y   -XX:AdaptiveSizeThroughPutPolicy=<value> uintx         Y   -XX:AdaptiveTimeWeight=<value> uintx     Y Y Y   -XX:+AdjustConcurrency bool Y Y Y Y Y     HotSpot Performance Tuning -XX:AliasLevel=<value> intx Y Y Y Y Y   -XX:+AllowUserSignalHandlers bool Y Y Y Y Y Do not complain if the application installs signal handlers (Solaris Only)   Java HotSpot VM Options -XX:AltStackSize=<value> intx Y Y Y Y   Alternate signal stack size (in Kbytes, Solaris Only)   Java HotSpot VM Options -XX:+AlwaysCompileLoopMethods bool Y Y Y Y Y   -XX:+AlwaysTenure bool     Y Y Y   -XX:AppendRatio=<value> intx         Y   -XX:+BackgroundCompilation bool Y Y Y Y Y Enables or disables JIT compilation in the background. When enabled, interpreted methods are still executed until background compilation is complete.   The Java HotSpot Virtual Machine Client Compiler -XX:BaseFootPrintEstimate=<value> uintx     Y Y Y   -XX:+BindGCTaskThreadsToCPUs bool     Y Y Y   -XX:+BindScavengeThreads bool Y           -XX:+BlockOffsetArrayUseUnallocatedBlock bool     Y Y Y   -XX:+BytecodeVerificationLocal bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+BytecodeVerificationRemote bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:CICompilerCount=<value> intx Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+CICompilerCountPerCPU bool       Y Y   -XX:+CIDynamicCompilePriority bool Y Y Y       -XX:+CIMaxPriority bool   Y Y       -XX:+CITime bool   Y Y Y Y Time spent in JIT Compiler   Java HotSpot VM Options -XX:CMSAbortablePrecleanMinWorkPerIteration=<value> uintx         Y   -XX:CMSAbortablePrecleanWaitMillis=<value> intx         Y   -XX:CMSBitMapYieldQuantum=<value> uintx       Y Y   -XX:CMSBootstrapOccupancy=<value> intx         Y   -XX:+CMSClassUnloadingEnabled bool     Y Y Y It has been reported that for 1.5, this apparently needs to be combined with -XX:+CMSPermGenSweepingEnabled in order to take effect.   Java Developer Connection Bug Parade -XX:+CMSCompactWhenClearAllSoftRefs bool     Y Y Y   -XX:CMSDictionaryChoice=<value> intx   Y         -XX:CMSExpAvgFactor=<value> uintx       Y Y   -XX:CMSFullGCsBeforeCompaction=<value> uintx     Y Y Y Parameter that affects compaction of the old generation. If at least this number of concurrent collections has not succeeded between full collection, do a compaction on full collections. If 0, always do compactions on full collections when UseCMSCompactAtFullCollection is true   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:CMSIncrementalDutyCycle=<value> uintx       Y Y   -XX:CMSIncrementalDutyCycleMin=<value> uintx       Y Y   -XX:+CMSIncrementalMode bool       Y Y   -XX:CMSIncrementalOffset=<value> uintx       Y Y   -XX:+CMSIncrementalPacing bool       Y Y   -XX:CMSIncrementalSafetyFactor=<value> uintx       Y Y   -XX:CMSIndexedFreeListReplenish=<value> uintx     Y Y Y   -XX:CMSInitiatingOccupancyFraction=<value> intx     Y Y Y Sets the threshold percentage of the used heap in the old generation at which the CMS collection takes place. For example, if set to 60, the CMS collector will be initiated every time the old generation becomes 60% full. By default, this threshold is calculated at run time, and the CMS collector might be triggered only when the old generation heap is about 80-90% full. Tuning this value can improve performance in many cases. Since the CMS collector does not suspend the mutators as it sweeps and frees memory, setting this switch can ensure that enough free memory is available for object promotion from the young generation as more data is allocated by the application. Sometimes, if this switch is not tuned, CMS collection might not be able to keep up and may fail, eventually triggering the default stop-the-world mark-compact collector. Available from J2SE1.4.1.   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine Turbo-charging Java HotSpot Virtual Machine -XX:+CMSLoopWarn bool     Y Y Y   -XX:CMSMarkStackSize=<value> uintx   Y Y Y Y   -XX:CMSMarkStackSizeMax=<value> uintx         Y   -XX:CMSMaxAbortablePrecleanLoops=<value> uintx         Y   -XX:CMSMaxAbortablePrecleanTime=<value> intx         Y   -XX:+CMSNoWarning bool   Y Y         Java Developer Connection Bug Parade -XX:+CMSParallelRemarkEnabled bool       Y Y Attempt to descrease remark pauses when used with -XX:+UseParNewGC.   Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:+CMSPermGenPrecleaningEnabled bool     Y Y Y   -XX:+CMSPermGenSweepingEnabled bool     Y Y Y It has been reported that for 1.5, this apparently needs to be combined with -XX:+CMSClassUnloadingEnabled in order to take effect. -XX:CMSPrecleanDenominator=<value> uintx   Y Y Y Y   -XX:CMSPrecleanIter=<value> uintx   Y Y Y Y   -XX:CMSPrecleanNumerator=<value> uintx   Y Y Y Y   -XX:+CMSPrecleanRefLists1 bool         Y   -XX:+CMSPrecleanRefLists2 bool         Y   -XX:CMSPrecleanThreshold=<value> uintx   Y Y Y Y   -XX:+CMSPrecleaningEnabled bool   Y Y Y Y   -XX:CMSRescanMultiple=<value> uintx       Y Y   -XX:CMSRevisitStackSize=<value> uintx     Y Y Y   -XX:CMSSamplingGrain=<value> uintx         Y   -XX:CMSScheduleRemarkEdenPenetration=<value> uintx         Y   -XX:CMSScheduleRemarkEdenSizeThreshold=<value> uintx         Y   -XX:CMSScheduleRemarkSamplingRatio=<value> uintx         Y   -XX:CMSTriggerRatio=<value> intx     Y Y Y   -XX:CMSWaitDuration=<value> intx     Y Y Y   -XX:CMSWorkQueueDrainThreshold=<value> uintx       Y Y   -XX:+CMSYield bool   Y Y Y Y   -XX:CMSYieldQuantum=<value> intx   Y Y       -XX:+CheckJNICalls bool Y Y Y Y Y   -XX:+CheckUnsafeOps bool   Y Y Y Y   -XX:+ClassUnloading bool Y Y Y Y Y   -XX:+ClipInlining bool Y Y Y Y Y   -XX:CodeCacheExpansionSize=<value> intx Y Y Y Y Y   -XX:CodeCacheMinimumFreeSpace=<value> uintx Y Y Y Y Y   -XX:+CodeForP6 bool Y             Java Developer Connection Bug Parade -XX:+CollectGen0First bool   Y Y Y Y   -XX:CompilationPolicyChoice=<value> intx   Y Y Y Y   -XX:CompilationRepeat=<value> intx       Y Y   -XX:CompileCommand=<value> ccstr       Y Y   -XX:CompileCommandFile=<value> ccstr       Y Y Allows you to specify alternate compiler command files. When used, this overrides the default behavior of the VM and the VM will NOT scan either the libjvm.sl directory or the current directory for a .hotspot_compiler file.   SDK release notes 1.3.1.12 -XX:CompileOnly=<value> ccstr       Y Y   -XX:CompileThreshold=<value> intx Y Y Y Y Y number of method invocations/branches before (re-)compiling [10,000 -server, 1,500 -client]   Java HotSpot VM Options -XX:+CompilerThreadHintNoPreempt bool       Y Y   -XX:CompilerThreadPriority=<value> intx       Y Y   -XX:CompilerThreadStackSize=<value> intx Y Y Y Y Y   -XX:+ConvertSleepToYield bool Y Y Y Y Y   -XX:+ConvertYieldToSleep bool Y Y Y Y Y   -XX:DefaultInitialRAMFraction=<value> uintx         Y   -XX:DefaultMaxRAM=<value> uintx         Y   -XX:DefaultMaxRAMFraction=<value> uintx         Y   -XX:DefaultThreadPriority=<value> intx       Y Y   -XX:DefaultTickInterval=<value> intx Y Y Y Y Y   -XX:+DefaultUseSpecLock bool Y Y           Java Developer Connection Bug Parade -XX:DeferThrSuspendLoopCount=<value> intx Y Y Y Y Y   -XX:DelayTickAdjustment=<value> intx Y Y Y Y Y   -XX:+DisableExplicitGC bool Y Y Y Y Y Disable calls to System.gc(), JVM still performs garbage collection when necessary   Java HotSpot VM Options Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine -XX:+DisplayVMOutput bool       Y Y   -XX:+DisplayVMOutputToStderr bool         Y   -XX:+DisplayVMOutputToStdout bool         Y   -XX:+DontCompileHugeMethods bool Y Y Y Y Y   -XX:+DontYieldALot bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+DumpSharedSpaces bool         Y   -XX:+EagerInitialization bool     Y         Java Developer Connection Bug Parade -XX:+EagerXrunInit bool       Y Y   -XX:+EnableJVMPIInstructionStartEvent bool Y Y Y Y Y Enables or disables the JVMPI event, JVMPI_EVENT_INSTRUCTION_START, which is sent when each instruction is issued by the interpreter   JavaTM Virtual Machine Profiler Interface (JVMPI) -XX:EventLogLength=<value> intx Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+ExitOnBadLibThread bool Y Y Y Y Y   -XX:+FastNMethodDependencies bool     Y Y Y     Java Developer Connection Bug Parade -XX:+FastTLABRefill bool         Y   -XX:+FasterSync bool Y           -XX:+FilterSpuriousWakeups bool Y Y Y Y Y   -XX:FloatCacheThreshold=<value> intx   Y         -XX:+ForceSharedSpaces bool         Y   -XX:+ForceTimeHighResolution bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+ForceUseSpecLock bool Y Y           Java Developer Connection Bug Parade -XX:FreqInlineSize=<value> intx Y Y Y Y Y Integer specifying maximum number of bytecode instructions in a frequently executed method which gets inlined.   Java HotSpot VM Options -XX:+FullSpeedJVMDI bool   Y Y Y       Java Developer Connection Bug Parade -XX:GCHeapFreeLimit=<value> uintx     Y Y Y Used with -XX:+UseParallelGC to help prevent out-of-memory exceptions from occuring during garbage collection. This parameter specifies the lower limit on the amount of space freed during a garbage collection in per cent of the maximum heap (default is 5).   Garbage Collector Ergonomics -XX:GCTaskTimeStampEntries=<value> uintx       Y Y   -XX:GCTimeLimit=<value> uintx     Y Y Y Used with -XX:+UseParallelGC to help prevent out-of-memory exceptions from occuring during garbage collection. This parameter specifies the upper limit on the amount of time spent in garbage collection in per cent of total time (default is 90)   Garbage Collector Ergonomics -XX:GCTimeRatio=<value> uintx         Y The ratio of GC time to application time, ratio being: 1 / (1 + nnn). For example -XX:GCTimeRatio=19 sets a goal of 5% of the total time for GC.   Garbage Collector Ergonomics -XX:+HandlePromotionFailure bool         Y   -XX:InitialCodeCacheSize=<value> intx Y Y Y Y Y     Java Developer Connection Bug Parade -XX:InitialSurvivorRatio=<value> uintx     Y Y Y     Java Developer Connection Bug Parade -XX:InitialTenuringThreshold=<value> intx     Y Y Y   -XX:+Inline bool Y   Y Y Y     Java Developer Connection Bug Parade -XX:InlineSmallCode=<value> intx Y     Y     -XX:+InlineUnreachedCalls bool Y Y Y Y Y   -XX:+InstallMethods bool Y           -XX:InterpreterProfilePercentage=<value> intx   Y Y Y Y   -XX:+JVMPICheckGCCompatibility bool         Y   -XX:+JavaMonitorsInStackTrace bool Y Y Y Y Y Useful to display more stack trace information about monitors   Java Developer Connection Forums -XX:JavaPriority10_To_OSPriority=<value> intx       Y Y     Java Developer Connection Bug Parade -XX:JavaPriority1_To_OSPriority=<value> intx       Y Y   -XX:JavaPriority2_To_OSPriority=<value> intx       Y Y     Java Developer Connection Bug Parade -XX:JavaPriority3_To_OSPriority=<value> intx       Y Y     Java Developer Connection Bug Parade -XX:JavaPriority4_To_OSPriority=<value> intx       Y Y     Java Developer Connection Bug Parade -XX:JavaPriority5_To_OSPriority=<value> intx       Y Y     Java Developer Connection Bug Parade -XX:JavaPriority6_To_OSPriority=<value> intx       Y Y     Java Developer Connection Bug Parade -XX:JavaPriority7_To_OSPriority=<value> intx       Y Y     Java Developer Connection Bug Parade -XX:JavaPriority8_To_OSPriority=<value> intx       Y Y     Java Developer Connection Bug Parade -XX:JavaPriority9_To_OSPriority=<value> intx       Y Y     Java Developer Connection Bug Parade -XX:+LIRCacheLocals bool   Y Y Y Y     Java Developer Connection Bug Parade -XX:+LIRFillDelaySlots bool   Y Y Y Y   -XX:+LIROptimize bool   Y         -XX:+LIROptimizeDeleteOps bool   Y         -XX:+LIROptimizeFloats bool   Y         -XX:+LIROptimizeStack bool   Y         -XX:LargePageHeapSizeThreshold=<value> uintx         Y   -XX:LargePageSizeInBytes=<value> uintx   Y Y Y Y   -XX:LocalCacheThreshold=<value> intx   Y         -XX:+LogCompilation bool       Y Y     Java Developer Connection Bug Parade -XX:LogFile=<value> ccstr       Y Y     Java Developer Connection Bug Parade -XX:+LogVMOutput bool       Y Y     Java Developer Connection Bug Parade -XX:+ManagementServer bool         Y   -XX:MarkSweepAlwaysCompactCount=<value> intx Y Y Y Y Y     Java Developer Connection Bug Parade -XX:MarkSweepDeadRatio=<value> intx Y Y Y Y Y     Java Developer Connection Bug Parade -XX:MaxDirectMemorySize=<value> intx       Y Y     Java Developer Connection Bug Parade -XX:+MaxFDLimit bool Y Y Y Y Y Bump the number of file descriptors to max. (Solaris only)   Java HotSpot VM Options -XX:MaxGCMinorPauseMillis=<value> uintx         Y   -XX:MaxGCPauseMillis=<value> uintx         Y A hint to the virtual machine that pause times of nnn milliseconds or less are desired. The vm will adjust the java heap size and other gc-related parameters in an attempt to keep gc-induced pauses shorter than nnn milliseconds. Note that this may cause the vm to reduce overall throughput, and in some cases the vm will not be able to meet the desired pause time goal.   Garbage Collector Ergonomics -XX:MaxHeapFreeRatio=<value> intx Y Y Y Y Y heap free percentage (default 70)   Java HotSpot VM Options Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine HotSpot Performance Tuning -XX:MaxHeapSize=<value> uintx Y Y Y Y Y   -XX:MaxInlineLevel=<value> intx Y     Y       Java Developer Connection Bug Parade -XX:MaxInlineSize=<value> intx Y Y Y Y Y Integer specifying maximum number of bytecode instructions in a method which gets inlined.   Java HotSpot VM Options -XX:MaxJavaStackTraceDepth=<value> intx Y Y Y Y Y     Java Developer Connection Bug Parade -XX:MaxLiveObjectEvacuationRatio=<value> uintx Y Y Y Y Y     Java Developer Connection Forums -XX:MaxNewSize=<value> uintx Y Y Y Y Y Maximum size of new generation (in bytes) [32m sparc, 2.5m intel for 1.3, no limit for 1.4 as NewRatio is now used to determine MaxNewSize]   Frequently Asked Questions About the Java HotSpot VM Turbo-charging Java HotSpot Virtual Machine Java HotSpot VM Options -XX:MaxPermHeapExpansion=<value> uintx Y Y Y Y Y   -XX:MaxPermSize=<value> uintx Y Y Y Y Y Size of the Permanent Generation   Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Java HotSpot VM Options Tuning Garbage Collection with the 1.3.1 Java Virtual Machine -XX:MaxRecursiveInlineLevel=<value> intx Y     Y     -XX:MaxSurvivorShrinkRatio=<value> size_t Y           -XX:MaxTLABRatio=<value> uintx   Y Y Y     -XX:MaxTLERatio=<value> Y           -XX:MaxTenuringThreshold=<value> intx Y Y Y Y Y This switch determines how much the objects may age in the young generation before getting promoted to the older generation. The default value is 31. For a big enough young generation and "survivor space", the long-lived objects may be copied up to 31 times between the survivor spaces before they are finally promoted to the old generation.   Turbo-charging Java HotSpot Virtual Machine Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:MaxTickInterval=<value> intx Y Y Y Y Y   -XX:MinHeapDeltaBytes=<value> uintx   Y Y Y Y   -XX:MinHeapFreeRatio=<value> intx Y Y Y Y Y heap free percentage (default 40)   Java HotSpot VM Options Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine Tuning Garbage Collection with the 1.3.1 Java Virtual Machine -XX:MinOldHeapExpansion=<value> size_t Y           -XX:MinPermHeapExpansion=<value> uintx Y Y Y Y Y   -XX:MinSurvivorRatio=<value> uintx     Y Y Y   -XX:MinTLABSize=<value> uintx         Y   -XX:MinTickInterval=<value> intx Y Y Y Y Y   -XX:NMethodSweepInterval=<value> Y           -XX:NativeSynchronization=<value> ccstr         Y   -XX:+NeverTenure bool     Y Y Y   -XX:NewRatio=<value> intx Y Y Y Y Y Ratio of new/old generation sizes [sparc -server: 2, sparc -client: 4 (1.3) 8 (1.3.1+), intel: 12] -XX:NewSize=<value> uintx Y Y Y Y Y Default size of new generation (in bytes) [sparc 2.125M, intel: 640k]   Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine Frequently Asked Questions About the Java HotSpot VM Java HotSpot VM Options Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 -XX:NewSizeThreadIncrease=<value> uintx Y Y Y Y Y As more threads are created in a server application, the object allocation rate may increase with the number of active threads. The number of active threads is considered when adjusting the size of the young space, after a garbage collection. This flag specifies, in Kilobytes, the increment in young object space size, per active thread, to accomodate potentially faster object allocation rate.   Java HotSpotTM Server VM Version 2.0 for Win32 Platforms -XX:NmethodSweepFraction=<value> intx Y Y Y Y Y   -XX:OldPLABSize=<value> uintx     Y Y Y   -XX:OldSize=<value> uintx Y Y Y Y Y   -XX:OnError=<value> ccstr         Y The Hotspot JVM includes a fatal error hander that can run a user-supplied script or program if the JVM aborts. A debug tool can also connect to a hung JVM or core file using the Hotspot JVM serviceability agent connector.   J2SE 1.5 in a Nutshell -XX:OnStackReplacePercentage=<value> intx   Y Y Y Y   -XX:OnStackReplaceThreshold=<value> Y           -XX:+OptimizeSinglePrecision bool   Y         -XX:+OverrideDefaultLibthread bool Y Y Y Y Y On Solaris 9, this option is not necessary. On Solaris 8, J2SE? versions 1.3.1_02+ and 1.4+ require this option when using the alternate threads library. This option is not possible on pre-Solaris 8 operating environments.   Java Developer Connection Forums Java HotSpot VM Options (docs.sun.com) -XX:OversizedCarThreshold=<value> uintx   Y Y Y Y   -XX:ParCMSPromoteBlocksToClaim=<value> intx     Y Y Y   -XX:ParGCArrayScanChunk=<value> intx         Y   -XX:ParGCDesiredObjsFromOverflowList=<value> intx     Y Y Y   -XX:ParGCMaxArrayAsNormalObject=<value> intx     Y Y     -XX:ParallelGCBufferWastePct=<value> intx     Y Y Y   -XX:ParallelGCG1AllocBufferSize=<value> intx     Y Y Y   -XX:ParallelGCOldGenAllocBufferSize=<value> intx     Y Y Y   -XX:+ParallelGCRetainPLAB bool         Y   -XX:ParallelGCTermSpinLoopMS=<value> intx     Y Y Y   -XX:ParallelGCThreads=<value> uintx     Y Y Y This switch sets the number of parallel GC threads that the JVM must run for performing garbage collection in the young generation. The default value of n is equal to the number of CPUs on the system. However, it has been observed that tweaking this number may improve performance in some cases. An example might be that of multiple instances of JVM running on a single multi-CPU system. In this case, the number of parallel GC threads for each JVM may need to be set to less than the number of CPUs by using this switch. Available from J2SE1.4.1.   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine Turbo-charging Java HotSpot Virtual Machine -XX:ParallelGCToSpaceAllocBufferSize=<value> intx     Y Y Y   -XX:+ParallelGCVerbose bool     Y Y Y   -XX:+ParallelRefProcEnabled bool         Y   -XX:+ParkTLE bool Y           -XX:+PassParametersInRegisters bool Y           -XX:+PerfAllowAtExitRegistration bool     Y Y Y   -XX:+PerfBypassFileSystemCheck bool       Y Y   -XX:PerfDataMemorySize=<value> intx     Y Y Y     Java Developer Connection Bug Parade -XX:PerfDataSamplingInterval=<value> intx     Y Y Y   -XX:+PerfDataSaveToFile bool     Y Y Y     -XX:+PerfDisableSharedMem bool     Y Y Y     1.4.2 HotSpot Instrumentation -XX:PerfMaxStringConstLength=<value> intx     Y Y Y   -XX:PermGenPadding=<value> uintx     Y Y Y   -XX:PermMarkSweepDeadRatio=<value> intx Y Y Y Y Y     Java Developer Connection Bug Parade -XX:PermSize=<value> uintx Y Y Y Y Y Initial size of permanent generation   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:+PostSpinYield bool Y Y Y Y Y   -XX:PreBlockSpin=<value> intx Y Y Y Y Y   -XX:PreInflateSpin=<value> intx Y Y Y Y Y   -XX:+PreSpinYield bool Y Y Y Y Y   -XX:+PreferInterpreterNativeStubs bool Y Y Y Y Y   -XX:PrefetchCopyIntervalInBytes=<value> intx Y Y Y Y Y Prefetch n bytes ahead for scavenge copy destination area. The default is 0. The ideal value may vary depending on the processor.   HotSpot Technology Tools and HP-Specific Features -XX:PrefetchFieldsAhead=<value> intx   Y Y Y Y   -XX:PrefetchScanIntervalInBytes=<value> intx Y Y Y Y Y Prefetch n bytes ahead for scavenge scan area. The default is 0. The ideal value may vary depending on the processor.   HotSpot Technology Tools and HP-Specific Features -XX:PrefetchScavengeFieldsAhead=<value> Y         Prefetch the next n fields of objects during scavenge. The default is 0. The ideal value may vary depending on the processor.   HotSpot Technology Tools and HP-Specific Features -XX:+PreserveAllAnnotations bool         Y   -XX:PreserveMarkStackSize=<value> uintx         Y   -XX:PretenureSizeThreshold=<value> uintx   Y Y Y Y Objects size greater than this is directly allocated in the older generation   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:+PrintAdaptiveSizePolicy bool     Y Y Y Prints information about adaptive size policy   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 -XX:PrintCMSStatistics=<value> intx   Y Y Y Y If > 0, Print statistics about the concurrent collections. For example, the number of times the concurrent collection yield to a young generation collection and the number of cards precleaned   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 -XX:+PrintClassHistogram bool       Y Y Prints the all the java heap objects, their instance count and total space they occupy in the heap. The only downside is that you need to issue a SIGQUIT (see -Xsqnopause) which will leave the app running but will dump all of this data to stdout. Very useful to assist in identifying memory problems for example on a production platform where an CPU intensive profiler cannot be used. -XX:+PrintCommandLineFlags bool         Y     Java Developer Connection Bug Parade -XX:+PrintCompilation bool Y Y Y Y Y traces methods as compiled   Java HotSpot VM Options -XX:PrintFLSCensus=<value> intx     Y Y Y if > 0, print the populations of the CMS free lists   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 -XX:PrintFLSStatistics=<value> intx   Y Y Y Y If > 0, print statistics about the concurrent free lists. For example, a fragmentation parameter   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 -XX:+PrintGC bool Y Y Y Y Y     Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 -XX:+PrintGCApplicationConcurrentTime bool       Y Y Measure the amount of time the applications runs between collection pauses   Diagnosing a Garbage Collection problem -XX:+PrintGCApplicationStoppedTime bool       Y Y Measure the length of the collection pauses.   Diagnosing a Garbage Collection problem -XX:+PrintGCDetails bool   Y Y Y Y Gives some details about the GCs, such as size of the young and old generation before and after GCs, size of total heap, time it takes for a GC to happen in young and old generation, size of objects promoted at every GC etc.   Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Turbo-charging Java HotSpot Virtual Machine Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:+PrintGCTaskTimeStamps bool       Y Y   -XX:+PrintGCTimeStamps bool   Y Y Y Y Prints the times at which the GCs happen relative to the start of the application   Turbo-charging Java HotSpot Virtual Machine Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 GC Portal Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine -XX:+PrintHeapAtGC bool   Y Y Y Y Prints detailed GC info including heap occupancy before and after GC.   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 -XX:+PrintJNIResolving bool Y Y Y Y Y   -XX:+PrintParScavenge bool Y           -XX:+PrintScavenge bool Y             Java Developer Connection Bug Parade -XX:+PrintSharedSpaces bool         Y   -XX:+PrintTLAB bool   Y Y Y Y trace all the operations on TLAB's (Thread Allocation Buffers)   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:+PrintTLE bool Y           -XX:+PrintTenuringDistribution bool Y Y Y Y Y Gives the aging distribution of the allocated objects in the young generation. Tuning of -XX:NewSize, -XX:MaxNewSize, -XX:SurvivorRatio and -XX:MaxTenuringThreshold=0as described earlier, should be directed by the analysis of the output from this switch to determine that objects are not prematurely promoted to the old generation.   Turbo-charging Java HotSpot Virtual Machine Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine Tuning Garbage Collection with the 1.3.1 Java Virtual Machine GC Portal -XX:+PrintVMOptions bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:ProcessDistributionStride=<value> uintx     Y Y Y   -XX:ProcessingToTenuringRatio=<value> intx Y Y Y Y Y   -XX:+ProfileIntervals bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:ProfileIntervalsTicks=<value> intx Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+ProfileVM bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+ProfilerLight bool Y Y Y Y Y   -XX:+ProfilerPrintByteCodeStatistics bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+ProfilerRecordPC bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:PromotedPadding=<value> uintx         Y     Java Developer Connection Bug Parade -XX:QueuedAllocationWarningCount=<value> intx   Y Y Y Y     Java Developer Connection Bug Parade -XX:ReadSpinIterations=<value> intx Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+ReduceSignalUsage bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:RefDiscoveryPolicy=<value> intx     Y Y Y   -XX:+RequireSharedSpaces bool         Y   -XX:ReservedCodeCacheSize=<value> intx Y Y Y Y Y Reserved code cache size (in bytes) - maximum code cache size. [Solaris 64-bit: 1024m]   Java HotSpot VM Options -XX:+ResizeTLAB bool   Y Y Y Y Enable or disable resizing of TLABs. The -server VM has this option enabled by default.   Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:+ResizeTLE bool Y             Java Developer Connection Bug Parade -XX:+RewriteBytecodes bool   Y Y Y Y     Java Developer Connection Bug Parade -XX:+RewriteFrequentPairs bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+SafepointPolling bool         Y     Java Developer Connection Bug Parade -XX:+ScavengeBeforeFullGC bool     Y Y Y   -XX:ScavengeThreads=<value> Y           -XX:SelfDestructTimer=<value> intx Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+SerializeVMOutput bool       Y Y     Java Developer Connection Bug Parade -XX:SharedDummyBlockSize=<value> uintx         Y   -XX:SharedMiscDataSize=<value> uintx         Y   -XX:SharedReadOnlySize=<value> uintx         Y   -XX:SharedReadWriteSize=<value> uintx         Y   -XX:+ShowMessageBoxOnError bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:SliceSizeInCards=<value> Y           -XX:SoftRefLRUPolicyMSPerMB=<value> intx Y Y Y Y Y Starting with Java HotSpot VM implementations in J2SE 1.3.1, softly reachable objects will remain alive for some amount of time after the last time they were referenced. The default value is one second of lifetime per free megabyte in the heap. This value can be adjusted using the -XX:SoftRefLRUPolicyMSPerMB flag, which accepts integer values representing milliseconds per MB of free memory.   Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine Frequently Asked Questions About the Java HotSpot VM Tuning Garbage Collection with the 1.3.1 Java Virtual Machine Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine -XX:StackRedPages=<value> intx Y Y Y Y Y   -XX:StackShadowPages=<value> intx       Y Y     Java Developer Connection Bug Parade -XX:+StackTraceInThrowable bool Y Y Y Y Y Enable or disable stack traces in exceptions.   The Java HotSpot Virtual Machine Client Compiler -XX:StackYellowPages=<value> intx Y Y Y Y Y   -XX:Stage2CompileThreshold=<value> intx   Y         -XX:+StagedCompilation bool   Y         -XX:StarvationMonitorInterval=<value> intx Y Y Y Y Y   -XX:SurvivorPadding=<value> uintx     Y Y Y   -XX:SurvivorRatio=<value> intx Y Y Y Y Y Sets the ratio of the survivor spaces (there are two) to the whole of the young generation.   Turbo-charging Java HotSpot Virtual Machine A Test of Java Virtual Machine Performance Tuning Garbage Collection with the 1.3.1 Java Virtual Machine Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine Frequently Asked Questions About the Java HotSpot VM Java HotSpot VM Options Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:TLABAllocationWeight=<value> uintx         Y   -XX:TLABFragmentationRatio=<value> uintx   Y Y Y     -XX:TLABRefillWasteFraction=<value> uintx         Y   -XX:TLABSize=<value> uintx   Y Y Y Y Set the size of the TLAB in bytes.   Java and Solaris Threading -XX:+TLABStats bool         Y   -XX:TLABThreadRatio=<value> uintx   Y Y Y       Java Developer Connection Bug Parade -XX:TLABWasteIncrement=<value> uintx         Y   -XX:TLABWasteTargetPercent=<value> uintx         Y   -XX:TLEFragmentationRatio=<value> Y           -XX:TLESize=<value> size_t Y         Sets the size of the TLEs (in bytes)   Java and Solaris Threading -XX:TLEThreadRatio=<value> Y             Java Developer Connection Bug Parade -XX:TargetSurvivorOccupationRatio=<value> size_t Y           -XX:TargetSurvivorPadding=<value> size_t Y           -XX:TargetSurvivorRatio=<value> intx Y Y Y Y Y This flag sets the desired percentage of the survivor space heap which must be used before objects are promoted to the old generation. For example, setting z to 90 would mean that 90% of the survivor space must be used before the young generation is considered full and objects are promoted to the old generation. This would allow objects to age more in the young generation before being tenured. The default value is 50.   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine Java HotSpot VM Options -XX:TenuredGenerationSizeIncrement=<value> uintx         Y   -XX:TenuredGenerationSizeSupplement=<value> uintx         Y   -XX:TenuredGenerationSizeSupplementDecay=<value> uintx         Y   -XX:ThreadPriorityPolicy=<value> intx         Y   -XX:+ThreadPriorityVerbose bool       Y Y     Java Developer Connection Bug Parade -XX:ThreadSafetyMargin=<value> intx         Y   -XX:ThreadStackSize=<value> intx Y Y Y Y Y Thread Stack Size (in Kbytes) (0 means use default stack size) [Sparc: 512, Solaris Intel: 256, Sparc 64bit: 1024 all others 0]   Java HotSpot VM Options -XX:ThresholdTolerance=<value> uintx     Y Y Y   -XX:Tier2CompileThreshold=<value> intx     Y Y Y   -XX:+TieredCompilation bool     Y Y Y   -XX:+TraceClassLoading bool Y Y Y Y Y Display classes as they are loaded. Similar to -verbose:class -XX:+TraceClassLoadingPreorder bool       Y Y   -XX:+TraceClassResolution bool       Y Y   -XX:+TraceClassUnloading bool Y Y Y Y Y Display classes as they are unloaded.   Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:+TraceFailedVMTextSegmentRetarget bool   Y Y       -XX:+TraceGen0Time bool   Y Y Y Y   -XX:+TraceGen1Time bool   Y Y Y Y   -XX:TraceJVMTI=<value> ccstr         Y     Java Developer Connection Bug Parade -XX:+TraceJVMTIObjectTagging bool         Y   -XX:TypeProfileFailureLimit=<value> intx   Y Y Y Y   -XX:TypeProfileMinimumRatio=<value> intx   Y Y Y Y   -XX:Ultra3PrefetchCopyIntervalInBytes=<value> Y           -XX:Ultra3PrefetchScanIntervalInBytes=<value> Y           -XX:Ultra3PrefetchScavengeFieldsAhead=<value> Y           -XX:+UnlockDiagnosticVMOptions bool       Y Y     Java Developer Connection Bug Parade -XX:+Use486InstrsOnly bool   Y Y Y Y   -XX:+UseAdaptiveGCBoundary bool         Y   -XX:+UseAdaptiveGenerationSizePolicyAtMajorCollection bool         Y   -XX:+UseAdaptiveGenerationSizePolicyAtMinorCollection bool         Y   -XX:+UseAdaptiveSizePolicy bool     Y Y Y Automatically sizes the young generation and chooses an optimum survivor ratio to maximize performance.   Garbage Collector Ergonomics Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:+UseAdaptiveSizePolicyAggressiveFootprintGoal bool         Y   -XX:+UseAdaptiveSizePolicyFootprintGoal bool         Y   -XX:+UseAdaptiveSizePolicyWithSystemGC bool         Y   -XX:+UseAdaptiveSizeScaleFootprintChangeByRatio bool         Y   -XX:+UseAdaptiveSizeScaleThroughputChangeByRatio bool         Y   -XX:+UseAltSigs bool Y   Y Y Y On the Solaris operating environment, the VM uses SIGUSR1 by default, which can sometimes conflict with applications that signal-chain SIGUSR1. -XX:+UseAltSigs will cause the VM to use signals other than SIGUSR1 and SIGUSR2 as the default.   Java HotSpot VM Options -XX:+UseBiasedLocking bool         Y This option first appears in 1.5.0_06. Enables a technique for improving the performance of uncontended synchronization. Some applications with significant amounts of uncontended synchronization may attain significant speedups with this flag enabled.   Java Tuning White Paper -XX:+UseBoundThreads bool Y Y Y Y Y Bind user level threads (Solaris only)   A Test of Java Virtual Machine Performance Java HotSpot VM Options Java and Solaris Threading Frequently Asked Questions About the Java HotSpot VM -XX:+UseC2CallingConventions bool Y Y Y Y       Java Developer Connection Bug Parade -XX:+UseCMSBestFit bool     Y Y Y   -XX:+UseCMSCollectionPassing bool     Y Y Y   -XX:+UseCMSCompactAtFullCollection bool     Y Y Y Normally the concurrent low pause collector does not copy nor compact the live objects. A garbage collection is done without moving the live objects. If fragmentation becomes a problem, allocate a larger heap. In 1.4.2 if fragmentation in the tenured generation becomes a problem, a compaction of the tenured generation will be done although not concurrently. In 1.4.1 that compaction will occur if the UseCMSCompactAtFullCollection option is turned on.   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:+UseCMSInitiatingOccupancyOnly bool     Y Y Y Used to enabled/disable the use of the anticipated promotions to start a concurrent collection set   Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine -XX:+UseCompiler bool   Y Y Y Y   -XX:+UseCompilerSafepoints bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+UseConcMarkSweepGC bool   Y Y Y Y This flag turns on concurrent garbage collection in the old generation. Available from J2SE1.4.1.   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine Turbo-charging Java HotSpot Virtual Machine Java HotSpot VM Options -XX:+UseDefaultStackSize bool Y Y Y Y Y   -XX:+UseFastAccessorMethods bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+UseFastEmptyMethods bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+UseFastJNIAccessors bool         Y     Java Developer Connection Bug Parade -XX:+UseFixedFrameSize bool   Y Y Y       Java Developer Connection Bug Parade -XX:+UseForcedSuspension bool     Y Y       Java Developer Connection Bug Parade -XX:+UseGCTaskAffinity bool     Y Y Y   -XX:+UseHeavyMonitors bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+UseISM bool Y Y Y Y Y Intimate Shared Memory   Big Heaps and Intimate Shared Memory (ISM) Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Java HotSpot VM Options -XX:+UseInterpreter bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+UseLWPSynchronization bool Y Y Y Y Y Use LWP-based instead of thread based synchronization. Default is on in J2SE 1.4.0 or higher. (Solaris only)   Java and Solaris Threading Java HotSpot VM Options -XX:+UseLargePageSize bool   Y Y       -XX:+UseLoopCounter bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+UseMPSS bool   Y Y Y Y Use Multiple Page Size Support (Solaris 9 only) w/4mb pages for the heap. Do not use with ISM as this replaces the need for ISM.   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Java HotSpot VM Options -XX:+UseNewFeature1 bool       Y Y   -XX:+UseNewFeature2 bool       Y Y   -XX:+UseNewFeature3 bool       Y Y   -XX:+UseNewFeature4 bool       Y Y   -XX:+UseOnStackReplacement bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+UseOversizedCarHandling bool   Y Y Y Y   -XX:+UsePSAdaptiveSurvivorSizePolicy bool         Y   -XX:+UseParNewGC bool     Y Y Y This flag turns on parallel garbage collection in the young generation. It can be enabled together with the CMS collector in the old generation. Available in J2SE1.4.1 on an experimental basis.   Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine Diagnosing a Garbage Collection problem Turbo-charging Java HotSpot Virtual Machine -XX:+UseParallelGC bool     Y Y Y This flag also turns on parallel garbage collection policy in the young generation; however, it does not work with the CMS collector in the old generation. It is more suitable for enterprise applications which can benefit from very large young generation heaps.   Garbage Collector Ergonomics Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine Turbo-charging Java HotSpot Virtual Machine -XX:+UseParallelScavenge bool Y             Java Developer Connection Forums -XX:+UsePerfData bool     Y Y Y     1.4.2 HotSpot Instrumentation -XX:+UsePermISM bool Y Y Y Y Y     HotSpot Performance Tuning -XX:+UseRecompilation bool Y             Java Developer Connection Bug Parade -XX:+UseResizableSurvivorSpaces bool Y           -XX:+UseSerialGC bool         Y Enable the "legacy" serial garbage collector. The 1.5+ collectors are generally more robust now, and this garbage collector will not be supported much longer   Garbage Collector Ergonomics -XX:+UseSharedSpaces bool         Y     Java Developer Connection Bug Parade -XX:+UseSignalChaining bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+UseSpecLock bool Y Y           Java Developer Connection Bug Parade -XX:+UseSpinning bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+UseSplitVerifier bool         Y   -XX:UseSSE=<value> intx         Y From Bug 5108893, The option probably indicates whether the compiler should make use of the processor's SSEi instructions and is only available in server VMs. -XX:+UseSuspendResumeThreadLists bool       Y Y   -XX:+UseTLAB bool   Y Y Y Y Turn off thread-local object allocation   Java HotSpot VM Options Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Java and Solaris Threading -XX:+UseTLE bool Y         Turn off thread local portions of the heap in the young generation   Java HotSpot VM Options Java and Solaris Threading -XX:+UseThreadPriorities bool Y Y Y Y Y Use native thread priorities   HotSpot Performance Tuning Java HotSpot VM Options -XX:+UseTrainGC bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+UseTypeProfile bool Y Y Y Y Y     Java Developer Connection Bug Parade -XX:+VMThreadHintNoPreempt bool       Y Y   -XX:VMThreadPriority=<value> intx       Y Y   -XX:VMThreadStackSize=<value> intx Y Y Y Y Y     Java Developer Connection Bug Parade -XX:ValueMapBucketInitialSize=<value> intx   Y         -XX:ValueMapBucketMaxSize=<value> intx   Y         -XX:ValueMapMaxSize=<value> intx   Y         -XX:+VerifyBeforeIteration bool         Y   -XX:YoungGenerationSizeIncrement=<value> uintx         Y   -XX:YoungGenerationSizeSupplement=<value> uintx         Y   -XX:YoungGenerationSizeSupplementDecay=<value> uintx         Y   -XX:YoungPLABSize=<value> uintx     Y Y Y   -XX:+ZeroTLAB bool   Y Y Y Y     Java Developer Connection Bug Parade -XX:+ZeroTLE bool Y             Java Developer Connection Bug Parade

References: JVM Performance Documentation Analyzing Stack Traces Turbo-charging Java HotSpot Virtual Machine Java HotSpot VM Options Tuning Garbage Collection with the 1.3.1 Java Virtual Machine Java and Solaris Threading Frequently Asked Questions about Garbage Collection in the HotspotTM JavaTM Virtual Machine Tuning Garbage Collection with the 1.4.2 Java[tm] Virtual Machine Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1 Big Heaps and Intimate Shared Memory (ISM) A Test of Java Virtual Machine Performance HotSpot Performance Tuning The Java HotSpot Virtual Machine Client Compiler Java Developer Connection Bug Parade SDK release notes 1.3.1.12 JavaTM Virtual Machine Profiler Interface (JVMPI) Garbage Collector Ergonomics Java Developer Connection Forums Frequently Asked Questions About the Java HotSpot VM Java HotSpotTM Server VM Version 2.0 for Win32 Platforms J2SE 1.5 in a Nutshell 1.4.2 HotSpot Instrumentation HotSpot Technology Tools and HP-Specific Features Diagnosing a Garbage Collection problem GC Portal HotSpot Performance Tuning Java HotSpot VM Options (docs.sun.com) Java Tuning White Paper

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