想写一篇jvm的工具入门

为什么要写一个jvm的工具入门呢，一是自己也不会，二是因为不会所以想学一下，还有就是这个确实很重要，对学习jvm有很多的用处，对定位问题有很大的便利，以前毕业那会我记得有个笔试，知道JAVA_HOME/bin目录的工具吗，例举下3个以上，并说说有什么用，可以怎么使用，，，，我只能说呵呵了，写代码哪里要注意这么多哈

一、基础了解

我们一般安装java，首先都会来一个java命令（现阶段java8和11用的人比较多，我这里还是8）

D:\Data\lugh1>java

用法: java [-options] class [args...]

           (执行类)

   或  java [-options] -jar jarfile [args...]

           (执行 jar 文件)

其中选项包括:

    -d32          使用  位数据模型 (如果可用)

    -d64          使用  位数据模型 (如果可用)

    -server       选择 "server" VM

                  默认 VM 是 server.

    -cp <目录和 zip/jar 文件的类搜索路径>

    -classpath <目录和 zip/jar 文件的类搜索路径>

                  用 ; 分隔的目录, JAR 档案

                  和 ZIP 档案列表, 用于搜索类文件。

    -D<名称>=<值>

                  设置系统属性

    -verbose:[class|gc|jni]

                  启用详细输出

    -version      输出产品版本并退出

    -version:<值>

                  警告: 此功能已过时, 将在

                  未来发行版中删除。

                  需要指定的版本才能运行

    -showversion  输出产品版本并继续

    -jre-restrict-search | -no-jre-restrict-search

                  警告: 此功能已过时, 将在

                  未来发行版中删除。

                  在版本搜索中包括/排除用户专用 JRE

    -? -help      输出此帮助消息

    -X            输出非标准选项的帮助

    -ea[:<packagename>...|:<classname>]

    -enableassertions[:<packagename>...|:<classname>]

                  按指定的粒度启用断言

    -da[:<packagename>...|:<classname>]

    -disableassertions[:<packagename>...|:<classname>]

                  禁用具有指定粒度的断言

    -esa | -enablesystemassertions

                  启用系统断言

    -dsa | -disablesystemassertions

                  禁用系统断言

    -agentlib:<libname>[=<选项>]

                  加载本机代理库 <libname>, 例如 -agentlib:hprof

                  另请参阅 -agentlib:jdwp=help 和 -agentlib:hprof=help

    -agentpath:<pathname>[=<选项>]

                  按完整路径名加载本机代理库

    -javaagent:<jarpath>[=<选项>]

                  加载 Java 编程语言代理, 请参阅 java.lang.instrument

    -splash:<imagepath>

                  使用指定的图像显示启动屏幕

参数分为三类，分别是：

标准参数（很稳定的）

-help

-version

-X参数（非标准参数，不能保证被所有的JVM实现都支持）

-Xint

-Xcomp

-XX参数（使用率较高）

-XX:newSize

-XX:+UseSerialGC

反正以前我是不知道-X，-XX，+UseSerialGC中的+号是什么，或许现在知道，好像也比较容易忘记，因为也没经常使用呀

来试一下java -X

D:\Data\lugh1>java -X

    -Xmixed           混合模式执行 (默认)

    -Xint             仅解释模式执行

    -Xbootclasspath:<用 ; 分隔的目录和 zip/jar 文件>

                      设置搜索路径以引导类和资源

    -Xbootclasspath/a:<用 ; 分隔的目录和 zip/jar 文件>

                      附加在引导类路径末尾

    -Xbootclasspath/p:<用 ; 分隔的目录和 zip/jar 文件>

                      置于引导类路径之前

    -Xdiag            显示附加诊断消息

    -Xnoclassgc       禁用类垃圾收集

    -Xincgc           启用增量垃圾收集

    -Xloggc:<file>    将 GC 状态记录在文件中 (带时间戳)

    -Xbatch           禁用后台编译

    -Xms<size>        设置初始 Java 堆大小

    -Xmx<size>        设置最大 Java 堆大小

    -Xss<size>        设置 Java 线程堆栈大小

    -Xprof            输出 cpu 配置文件数据

    -Xfuture          启用最严格的检查, 预期将来的默认值

    -Xrs              减少 Java/VM 对操作系统信号的使用 (请参阅文档)

    -Xcheck:jni       对 JNI 函数执行其他检查

    -Xshare:off       不尝试使用共享类数据

    -Xshare:auto      在可能的情况下使用共享类数据 (默认)

    -Xshare:on        要求使用共享类数据, 否则将失败。

    -XshowSettings    显示所有设置并继续

    -XshowSettings:all

                      显示所有设置并继续

    -XshowSettings:vm 显示所有与 vm 相关的设置并继续

    -XshowSettings:properties

                      显示所有属性设置并继续

    -XshowSettings:locale

                      显示所有与区域设置相关的设置并继续

-Xms<size> 设置初始 Java 堆大小
-Xmx<size> 设置最大 Java 堆大小
-Xss<size> 设置 Java 线程堆栈大小

是不是觉得上面几个参数很熟悉，就是日常调整堆和栈大小的参数呀，很好记吧，比如java ‐Xms2048m ‐Xmx2048m class_name

在解释模式(interpreted mode)下，-Xint标记会强制JVM执行所有的字节码，当然这会降低运行速度，通常低10倍或更多

-Xcomp参数与它（-Xint）正好相反，JVM在第一次使用时会把所有的字节码编译成本地代码，从而带来最大程度的优化。然而，很多应用在使用-Xcomp也会有一些性能损失，当然这比使用-Xint损失的少，原因是-xcomp没有让JVM启用JIT编译器的全部功能。JIT编译器可以对是否需要编译做判断，如果所有代码都进行编译的话，对于一些只执行一次的代码就没有意义了
-Xmixed是混合模式，将解释模式与编译模式进行混合使用，由jvm自己决定，这是jvm默认的模式，也是推荐使用的模式

接下来了解下-XX参数：

-XX参数的使用有2种方式，一种是boolean类型，一种是非boolean类型（好像有点废话）

boolean类型

格式：-XX:[+-]

如：-XX:+DisableExplicitGC 表示禁用手动调用gc操作，也就是说调用System.gc()无效，+表示启用，-表示禁止吧

非boolean类型

格式：-XX:

如：-XX:NewRatio= 表示新生代和老年代的比值

那么多参数怎么记得呢，可以使用java -XX:+PrintFlagsFinal查看所有参数呀

D:\MyData\lugh1>java -XX:+PrintFlagsFinal

[Global flags]

     intx ActiveProcessorCount                      = -                                  {product}

    uintx AdaptiveSizeDecrementScaleFactor          =                                    {product}

    uintx AdaptiveSizeMajorGCDecayTimeScale         =                                   {product}

    uintx AdaptiveSizePausePolicy                   =                                    {product}

    uintx AdaptiveSizePolicyCollectionCostMargin    =                                   {product}

    uintx AdaptiveSizePolicyInitializingSteps       =                                   {product}

    uintx AdaptiveSizePolicyOutputInterval          =                                    {product}

    uintx AdaptiveSizePolicyWeight                  =                                   {product}

    uintx AdaptiveSizeThroughPutPolicy              =                                    {product}

    uintx AdaptiveTimeWeight                        =                                   {product}

     bool AdjustConcurrency                         = false                               {product}

     bool AggressiveHeap                            = false                               {product}

     bool AggressiveOpts                            = false                               {product}

     intx AliasLevel                                =                                    {C2 product}

     bool AlignVector                               = false                               {C2 product}

     intx AllocateInstancePrefetchLines             =                                    {product}

     intx AllocatePrefetchDistance                  =                                  {product}

     intx AllocatePrefetchInstr                     =                                    {product}

     intx AllocatePrefetchLines                     =                                    {product}

     intx AllocatePrefetchStepSize                  =                                   {product}

     intx AllocatePrefetchStyle                     =                                    {product}

     bool AllowJNIEnvProxy                          = false                               {product}

     bool AllowNonVirtualCalls                      = false                               {product}

     bool AllowParallelDefineClass                  = false                               {product}

     bool AllowUserSignalHandlers                   = false                               {product}

     bool AlwaysActAsServerClassMachine             = false                               {product}

     bool AlwaysCompileLoopMethods                  = false                               {product}

     bool AlwaysLockClassLoader                     = false                               {product}

     bool AlwaysPreTouch                            = false                               {product}

     bool AlwaysRestoreFPU                          = false                               {product}

     bool AlwaysTenure                              = false                               {product}

     bool AssertOnSuspendWaitFailure                = false                               {product}

     bool AssumeMP                                  = false                               {product}

     intx AutoBoxCacheMax                           =                                  {C2 product}

    uintx AutoGCSelectPauseMillis                   =                                 {product}

     intx BCEATraceLevel                            =                                    {product}

     intx BackEdgeThreshold                         =                               {pd product}

     bool BackgroundCompilation                     = true                                {pd product}

    uintx BaseFootPrintEstimate                     =                            {product}

     intx BiasedLockingBulkRebiasThreshold          =                                   {product}

     intx BiasedLockingBulkRevokeThreshold          =                                   {product}

     intx BiasedLockingDecayTime                    =                                {product}

     intx BiasedLockingStartupDelay                 =                                 {product}

     bool BindGCTaskThreadsToCPUs                   = false                               {product}

     bool BlockLayoutByFrequency                    = true                                {C2 product}

     intx BlockLayoutMinDiamondPercentage           =                                   {C2 product}

     bool BlockLayoutRotateLoops                    = true                                {C2 product}

     bool BranchOnRegister                          = false                               {C2 product}

     bool BytecodeVerificationLocal                 = false                               {product}

     bool BytecodeVerificationRemote                = true                                {product}

     bool C1OptimizeVirtualCallProfiling            = true                                {C1 product}

     bool C1ProfileBranches                         = true                                {C1 product}

     bool C1ProfileCalls                            = true                                {C1 product}

     bool C1ProfileCheckcasts                       = true                                {C1 product}

     bool C1ProfileInlinedCalls                     = true                                {C1 product}

     bool C1ProfileVirtualCalls                     = true                                {C1 product}

     bool C1UpdateMethodData                        = true                                {C1 product}

     intx CICompilerCount                          :=                                    {product}

     bool CICompilerCountPerCPU                     = true                                {product}

     bool CITime                                    = false                               {product}

     bool CMSAbortSemantics                         = false                               {product}

    uintx CMSAbortablePrecleanMinWorkPerIteration   =                                  {product}

     intx CMSAbortablePrecleanWaitMillis            =                                  {manageable}

    uintx CMSBitMapYieldQuantum                     =                             {product}

    uintx CMSBootstrapOccupancy                     =                                   {product}

     bool CMSClassUnloadingEnabled                  = true                                {product}

    uintx CMSClassUnloadingMaxInterval              =                                    {product}

     bool CMSCleanOnEnter                           = true                                {product}

     bool CMSCompactWhenClearAllSoftRefs            = true                                {product}

    uintx CMSConcMarkMultiple                       =                                   {product}

     bool CMSConcurrentMTEnabled                    = true                                {product}

    uintx CMSCoordinatorYieldSleepCount             =                                   {product}

     bool CMSDumpAtPromotionFailure                 = false                               {product}

     bool CMSEdenChunksRecordAlways                 = true                                {product}

    uintx CMSExpAvgFactor                           =                                   {product}

     bool CMSExtrapolateSweep                       = false                               {product}

    uintx CMSFullGCsBeforeCompaction                =                                    {product}

    uintx CMSIncrementalDutyCycle                   =                                   {product}

    uintx CMSIncrementalDutyCycleMin                =                                    {product}

     bool CMSIncrementalMode                        = false                               {product}

    uintx CMSIncrementalOffset                      =                                    {product}

     bool CMSIncrementalPacing                      = true                                {product}

    uintx CMSIncrementalSafetyFactor                =                                   {product}

    uintx CMSIndexedFreeListReplenish               =                                    {product}

     intx CMSInitiatingOccupancyFraction            = -                                  {product}

    uintx CMSIsTooFullPercentage                    =                                   {product}

   double CMSLargeCoalSurplusPercent                = 0.950000                            {product}

   double CMSLargeSplitSurplusPercent               = 1.000000                            {product}

     bool CMSLoopWarn                               = false                               {product}

    uintx CMSMaxAbortablePrecleanLoops              =                                    {product}

     intx CMSMaxAbortablePrecleanTime               =                                 {product}

    uintx CMSOldPLABMax                             =                                 {product}

    uintx CMSOldPLABMin                             =                                   {product}

    uintx CMSOldPLABNumRefills                      =                                    {product}

    uintx CMSOldPLABReactivityFactor                =                                    {product}

     bool CMSOldPLABResizeQuicker                   = false                               {product}

    uintx CMSOldPLABToleranceFactor                 =                                    {product}

     bool CMSPLABRecordAlways                       = true                                {product}

    uintx CMSParPromoteBlocksToClaim                =                                   {product}

     bool CMSParallelInitialMarkEnabled             = true                                {product}

     bool CMSParallelRemarkEnabled                  = true                                {product}

     bool CMSParallelSurvivorRemarkEnabled          = true                                {product}

    uintx CMSPrecleanDenominator                    =                                    {product}

    uintx CMSPrecleanIter                           =                                    {product}

    uintx CMSPrecleanNumerator                      =                                    {product}

     bool CMSPrecleanRefLists1                      = true                                {product}

     bool CMSPrecleanRefLists2                      = false                               {product}

     bool CMSPrecleanSurvivors1                     = false                               {product}

     bool CMSPrecleanSurvivors2                     = true                                {product}

    uintx CMSPrecleanThreshold                      =                                 {product}

     bool CMSPrecleaningEnabled                     = true                                {product}

     bool CMSPrintChunksInDump                      = false                               {product}

     bool CMSPrintEdenSurvivorChunks                = false                               {product}

     bool CMSPrintObjectsInDump                     = false                               {product}

    uintx CMSRemarkVerifyVariant                    =                                    {product}

     bool CMSReplenishIntermediate                  = true                                {product}

    uintx CMSRescanMultiple                         =                                   {product}

    uintx CMSSamplingGrain                          =                                {product}

     bool CMSScavengeBeforeRemark                   = false                               {product}

    uintx CMSScheduleRemarkEdenPenetration          =                                   {product}

    uintx CMSScheduleRemarkEdenSizeThreshold        =                              {product}

    uintx CMSScheduleRemarkSamplingRatio            =                                    {product}

   double CMSSmallCoalSurplusPercent                = 1.050000                            {product}

   double CMSSmallSplitSurplusPercent               = 1.100000                            {product}

     bool CMSSplitIndexedFreeListBlocks             = true                                {product}

     intx CMSTriggerInterval                        = -                                  {manageable}

    uintx CMSTriggerRatio                           =                                   {product}

     intx CMSWaitDuration                           =                                 {manageable}

    uintx CMSWorkQueueDrainThreshold                =                                   {product}

     bool CMSYield                                  = true                                {product}

    uintx CMSYieldSleepCount                        =                                    {product}

    uintx CMSYoungGenPerWorker                      =                             {pd product}

    uintx CMS_FLSPadding                            =                                    {product}

    uintx CMS_FLSWeight                             =                                   {product}

    uintx CMS_SweepPadding                          =                                    {product}

    uintx CMS_SweepTimerThresholdMillis             =                                   {product}

    uintx CMS_SweepWeight                           =                                   {product}

     bool CheckEndorsedAndExtDirs                   = false                               {product}

     bool CheckJNICalls                             = false                               {product}

     bool ClassUnloading                            = true                                {product}

     bool ClassUnloadingWithConcurrentMark          = true                                {product}

     intx ClearFPUAtPark                            =                                    {product}

     bool ClipInlining                              = true                                {product}

    uintx CodeCacheExpansionSize                    =                                {pd product}

    uintx CodeCacheMinimumFreeSpace                 =                               {product}

     bool CollectGen0First                          = false                               {product}

     bool CompactFields                             = true                                {product}

     intx CompilationPolicyChoice                   =                                    {product}

ccstrlist CompileCommand                            =                                     {product}

    ccstr CompileCommandFile                        =                                     {product}

ccstrlist CompileOnly                               =                                     {product}

     intx CompileThreshold                          =                                {pd product}

     bool CompilerThreadHintNoPreempt               = true                                {product}

     intx CompilerThreadPriority                    = -                                  {product}

     intx CompilerThreadStackSize                   =                                    {pd product}

    uintx CompressedClassSpaceSize                  =                           {product}

    uintx ConcGCThreads                             =                                    {product}

     intx ConditionalMoveLimit                      =                                    {C2 pd product}

     intx ContendedPaddingWidth                     =                                  {product}

     bool ConvertSleepToYield                       = true                                {pd product}

     bool ConvertYieldToSleep                       = false                               {product}

     bool CrashOnOutOfMemoryError                   = false                               {product}

     bool CreateMinidumpOnCrash                     = false                               {product}

     bool CriticalJNINatives                        = true                                {product}

     bool DTraceAllocProbes                         = false                               {product}

     bool DTraceMethodProbes                        = false                               {product}

     bool DTraceMonitorProbes                       = false                               {product}

     bool Debugging                                 = false                               {product}

    uintx DefaultMaxRAMFraction                     =                                    {product}

     intx DefaultThreadPriority                     = -                                  {product}

     intx DeferPollingPageLoopCount                 = -                                  {product}

     intx DeferThrSuspendLoopCount                  =                                 {product}

     bool DeoptimizeRandom                          = false                               {product}

     bool DisableAttachMechanism                    = false                               {product}

     bool DisableExplicitGC                         = false                               {product}

     bool DisplayVMOutputToStderr                   = false                               {product}

     bool DisplayVMOutputToStdout                   = false                               {product}

     bool DoEscapeAnalysis                          = true                                {C2 product}

     bool DontCompileHugeMethods                    = true                                {product}

     bool DontYieldALot                             = false                               {pd product}

    ccstr DumpLoadedClassList                       =                                     {product}

     bool DumpReplayDataOnError                     = true                                {product}

     bool DumpSharedSpaces                          = false                               {product}

     bool EagerXrunInit                             = false                               {product}

     intx EliminateAllocationArraySizeLimit         =                                   {C2 product}

     bool EliminateAllocations                      = true                                {C2 product}

     bool EliminateAutoBox                          = true                                {C2 product}

     bool EliminateLocks                            = true                                {C2 product}

     bool EliminateNestedLocks                      = true                                {C2 product}

     intx EmitSync                                  =                                    {product}

     bool EnableContended                           = true                                {product}

     bool EnableResourceManagementTLABCache         = true                                {product}

     bool EnableSharedLookupCache                   = true                                {product}

     bool EnableTracing                             = false                               {product}

    uintx ErgoHeapSizeLimit                         =                                    {product}

    ccstr ErrorFile                                 =                                     {product}

    ccstr ErrorReportServer                         =                                     {product}

   double EscapeAnalysisTimeout                     = 20.000000                           {C2 product}

     bool EstimateArgEscape                         = true                                {product}

     bool ExitOnOutOfMemoryError                    = false                               {product}

     bool ExplicitGCInvokesConcurrent               = false                               {product}

     bool ExplicitGCInvokesConcurrentAndUnloadsClasses  = false                               {product}

     bool ExtendedDTraceProbes                      = false                               {product}

    ccstr ExtraSharedClassListFile                  =                                     {product}

     bool FLSAlwaysCoalesceLarge                    = false                               {product}

    uintx FLSCoalescePolicy                         =                                    {product}

   double FLSLargestBlockCoalesceProximity          = 0.990000                            {product}

     bool FailOverToOldVerifier                     = true                                {product}

     bool FastTLABRefill                            = true                                {product}

     intx FenceInstruction                          =                                    {ARCH product}

     intx FieldsAllocationStyle                     =                                    {product}

     bool FilterSpuriousWakeups                     = true                                {product}

    ccstr FlightRecorderOptions                     =                                     {product}

     bool ForceNUMA                                 = false                               {product}

     bool ForceTimeHighResolution                   = false                               {product}

     intx FreqInlineSize                            =                                  {pd product}

   double G1ConcMarkStepDurationMillis              = 10.000000                           {product}

    uintx G1ConcRSHotCardLimit                      =                                    {product}

    uintx G1ConcRSLogCacheSize                      =                                   {product}

     intx G1ConcRefinementGreenZone                 =                                    {product}

     intx G1ConcRefinementRedZone                   =                                    {product}

     intx G1ConcRefinementServiceIntervalMillis     =                                  {product}

    uintx G1ConcRefinementThreads                   =                                    {product}

     intx G1ConcRefinementThresholdStep             =                                    {product}

     intx G1ConcRefinementYellowZone                =                                    {product}

    uintx G1ConfidencePercent                       =                                   {product}

    uintx G1HeapRegionSize                          =                                    {product}

    uintx G1HeapWastePercent                        =                                    {product}

    uintx G1MixedGCCountTarget                      =                                    {product}

     intx G1RSetRegionEntries                       =                                    {product}

    uintx G1RSetScanBlockSize                       =                                   {product}

     intx G1RSetSparseRegionEntries                 =                                    {product}

     intx G1RSetUpdatingPauseTimePercent            =                                   {product}

     intx G1RefProcDrainInterval                    =                                   {product}

    uintx G1ReservePercent                          =                                   {product}

    uintx G1SATBBufferEnqueueingThresholdPercent    =                                   {product}

     intx G1SATBBufferSize                          =                                 {product}

     intx G1UpdateBufferSize                        =                                  {product}

     bool G1UseAdaptiveConcRefinement               = true                                {product}

    uintx GCDrainStackTargetSize                    =                                   {product}

    uintx GCHeapFreeLimit                           =                                    {product}

    uintx GCLockerEdenExpansionPercent              =                                    {product}

     bool GCLockerInvokesConcurrent                 = false                               {product}

    uintx GCLogFileSize                             =                                 {product}

    uintx GCPauseIntervalMillis                     =                                    {product}

    uintx GCTaskTimeStampEntries                    =                                  {product}

    uintx GCTimeLimit                               =                                   {product}

    uintx GCTimeRatio                               =                                   {product}

    uintx HeapBaseMinAddress                        =                           {pd product}

     bool HeapDumpAfterFullGC                       = false                               {manageable}

     bool HeapDumpBeforeFullGC                      = false                               {manageable}

     bool HeapDumpOnOutOfMemoryError                = false                               {manageable}

    ccstr HeapDumpPath                              =                                     {manageable}

    uintx HeapFirstMaximumCompactionCount           =                                    {product}

    uintx HeapMaximumCompactionInterval             =                                   {product}

    uintx HeapSizePerGCThread                       =                             {product}

     bool IgnoreEmptyClassPaths                     = false                               {product}

     bool IgnoreUnrecognizedVMOptions               = false                               {product}

    uintx IncreaseFirstTierCompileThresholdAt       =                                   {product}

     bool IncrementalInline                         = true                                {C2 product}

    uintx InitialBootClassLoaderMetaspaceSize       =                              {product}

    uintx InitialCodeCacheSize                      =                              {pd product}

    uintx InitialHeapSize                          :=                            {product}

    uintx InitialRAMFraction                        =                                   {product}

   double InitialRAMPercentage                      = 1.562500                            {product}

    uintx InitialSurvivorRatio                      =                                    {product}

    uintx InitialTenuringThreshold                  =                                    {product}

    uintx InitiatingHeapOccupancyPercent            =                                   {product}

     bool Inline                                    = true                                {product}

    ccstr InlineDataFile                            =                                     {product}

     intx InlineSmallCode                           =                                 {pd product}

     bool InlineSynchronizedMethods                 = true                                {C1 product}

     bool InsertMemBarAfterArraycopy                = true                                {C2 product}

     intx InteriorEntryAlignment                    =                                   {C2 pd product}

     intx InterpreterProfilePercentage              =                                   {product}

     bool JNIDetachReleasesMonitors                 = true                                {product}

     bool JavaMonitorsInStackTrace                  = true                                {product}

     intx JavaPriority10_To_OSPriority              = -                                  {product}

     intx JavaPriority1_To_OSPriority               = -                                  {product}

     intx JavaPriority2_To_OSPriority               = -                                  {product}

     intx JavaPriority3_To_OSPriority               = -                                  {product}

     intx JavaPriority4_To_OSPriority               = -                                  {product}

     intx JavaPriority5_To_OSPriority               = -                                  {product}

     intx JavaPriority6_To_OSPriority               = -                                  {product}

     intx JavaPriority7_To_OSPriority               = -                                  {product}

     intx JavaPriority8_To_OSPriority               = -                                  {product}

     intx JavaPriority9_To_OSPriority               = -                                  {product}

     bool LIRFillDelaySlots                         = false                               {C1 pd product}

    uintx LargePageHeapSizeThreshold                =                            {product}

    uintx LargePageSizeInBytes                      =                                    {product}

     bool LazyBootClassLoader                       = true                                {product}

     intx LiveNodeCountInliningCutoff               =                                {C2 product}

     bool LogCommercialFeatures                     = false                               {product}

     intx LoopMaxUnroll                             =                                   {C2 product}

     intx LoopOptsCount                             =                                   {C2 product}

     intx LoopUnrollLimit                           =                                   {C2 pd product}

     intx LoopUnrollMin                             =                                    {C2 product}

     bool LoopUnswitching                           = true                                {C2 product}

     bool ManagementServer                          = false                               {product}

    uintx MarkStackSize                             =                              {product}

    uintx MarkStackSizeMax                          =                            {product}

    uintx MarkSweepAlwaysCompactCount               =                                    {product}

    uintx MarkSweepDeadRatio                        =                                    {product}

     intx MaxBCEAEstimateLevel                      =                                    {product}

     intx MaxBCEAEstimateSize                       =                                  {product}

    uintx MaxDirectMemorySize                       =                                    {product}

     bool MaxFDLimit                                = true                                {product}

    uintx MaxGCMinorPauseMillis                     =                           {product}

    uintx MaxGCPauseMillis                          =                           {product}

    uintx MaxHeapFreeRatio                          =                                  {manageable}

    uintx MaxHeapSize                              :=                           {product}

     intx MaxInlineLevel                            =                                    {product}

     intx MaxInlineSize                             =                                   {product}

     intx MaxJNILocalCapacity                       =                                {product}

     intx MaxJavaStackTraceDepth                    =                                 {product}

     intx MaxJumpTableSize                          =                                {C2 product}

     intx MaxJumpTableSparseness                    =                                    {C2 product}

     intx MaxLabelRootDepth                         =                                 {C2 product}

     intx MaxLoopPad                                =                                   {C2 product}

    uintx MaxMetaspaceExpansion                     =                              {product}

    uintx MaxMetaspaceFreeRatio                     =                                   {product}

    uintx MaxMetaspaceSize                          =                           {product}

    uintx MaxNewSize                               :=                            {product}

     intx MaxNodeLimit                              =                                {C2 product}

 uint64_t MaxRAM                                    =                                    {pd product}

    uintx MaxRAMFraction                            =                                    {product}

   double MaxRAMPercentage                          = 25.000000                           {product}

     intx MaxRecursiveInlineLevel                   =                                    {product}

    uintx MaxTenuringThreshold                      =                                   {product}

     intx MaxTrivialSize                            =                                    {product}

     intx MaxVectorSize                             =                                   {C2 product}

    uintx MetaspaceSize                             =                             {pd product}

     bool MethodFlushing                            = true                                {product}

    uintx MinHeapDeltaBytes                        :=                               {product}

    uintx MinHeapFreeRatio                          =                                    {manageable}

     intx MinInliningThreshold                      =                                  {product}

     intx MinJumpTableSize                          =                                   {C2 pd product}

    uintx MinMetaspaceExpansion                     =                               {product}

    uintx MinMetaspaceFreeRatio                     =                                   {product}

    uintx MinRAMFraction                            =                                    {product}

   double MinRAMPercentage                          = 50.000000                           {product}

    uintx MinSurvivorRatio                          =                                    {product}

    uintx MinTLABSize                               =                                 {product}

     intx MonitorBound                              =                                    {product}

     bool MonitorInUseLists                         = false                               {product}

     intx MultiArrayExpandLimit                     =                                    {C2 product}

     bool MustCallLoadClassInternal                 = false                               {product}

    uintx NUMAChunkResizeWeight                     =                                   {product}

    uintx NUMAInterleaveGranularity                 =                              {product}

    uintx NUMAPageScanRate                          =                                  {product}

    uintx NUMASpaceResizeRate                       =                           {product}

     bool NUMAStats                                 = false                               {product}

    ccstr NativeMemoryTracking                      = off                                 {product}

     bool NeedsDeoptSuspend                         = false                               {pd product}

     bool NeverActAsServerClassMachine              = false                               {pd product}

     bool NeverTenure                               = false                               {product}

    uintx NewRatio                                  =                                    {product}

    uintx NewSize                                  :=                             {product}

    uintx NewSizeThreadIncrease                     =                                 {pd product}

     intx NmethodSweepActivity                      =                                   {product}

     intx NmethodSweepCheckInterval                 =                                    {product}

     intx NmethodSweepFraction                      =                                   {product}

     intx NodeLimitFudgeFactor                      =                                 {C2 product}

    uintx NumberOfGCLogFiles                        =                                    {product}

     intx NumberOfLoopInstrToAlign                  =                                    {C2 product}

     intx ObjectAlignmentInBytes                    =                                    {lp64_product}

    uintx OldPLABSize                               =                                 {product}

    uintx OldPLABWeight                             =                                   {product}

    uintx OldSize                                  :=                             {product}

     bool OmitStackTraceInFastThrow                 = true                                {product}

ccstrlist OnError                                   =                                     {product}

ccstrlist OnOutOfMemoryError                        =                                     {product}

     intx OnStackReplacePercentage                  =                                  {pd product}

     bool OptimizeFill                              = true                                {C2 product}

     bool OptimizePtrCompare                        = true                                {C2 product}

     bool OptimizeStringConcat                      = true                                {C2 product}

     bool OptoBundling                              = false                               {C2 pd product}

     intx OptoLoopAlignment                         =                                   {pd product}

     bool OptoScheduling                            = false                               {C2 pd product}

    uintx PLABWeight                                =                                   {product}

     bool PSChunkLargeArrays                        = true                                {product}

     intx ParGCArrayScanChunk                       =                                   {product}

    uintx ParGCDesiredObjsFromOverflowList          =                                   {product}

     bool ParGCTrimOverflow                         = true                                {product}

     bool ParGCUseLocalOverflow                     = false                               {product}

    uintx ParallelGCBufferWastePct                  =                                   {product}

    uintx ParallelGCThreads                         =                                    {product}

     bool ParallelGCVerbose                         = false                               {product}

    uintx ParallelOldDeadWoodLimiterMean            =                                   {product}

    uintx ParallelOldDeadWoodLimiterStdDev          =                                   {product}

     bool ParallelRefProcBalancingEnabled           = true                                {product}

     bool ParallelRefProcEnabled                    = false                               {product}

     bool PartialPeelAtUnsignedTests                = true                                {C2 product}

     bool PartialPeelLoop                           = true                                {C2 product}

     intx PartialPeelNewPhiDelta                    =                                    {C2 product}

    uintx PausePadding                              =                                    {product}

     intx PerBytecodeRecompilationCutoff            =                                  {product}

     intx PerBytecodeTrapLimit                      =                                    {product}

     intx PerMethodRecompilationCutoff              =                                  {product}

     intx PerMethodTrapLimit                        =                                  {product}

     bool PerfAllowAtExitRegistration               = false                               {product}

     bool PerfBypassFileSystemCheck                 = false                               {product}

     intx PerfDataMemorySize                        =                                {product}

     intx PerfDataSamplingInterval                  =                                   {product}

    ccstr PerfDataSaveFile                          =                                     {product}

     bool PerfDataSaveToFile                        = false                               {product}

     bool PerfDisableSharedMem                      = false                               {product}

     intx PerfMaxStringConstLength                  =                                 {product}

     intx PreInflateSpin                            =                                   {pd product}

     bool PreferInterpreterNativeStubs              = false                               {pd product}

     intx PrefetchCopyIntervalInBytes               =                                  {product}

     intx PrefetchFieldsAhead                       =                                    {product}

     intx PrefetchScanIntervalInBytes               =                                  {product}

     bool PreserveAllAnnotations                    = false                               {product}

     bool PreserveFramePointer                      = false                               {pd product}

    uintx PretenureSizeThreshold                    =                                    {product}

     bool PrintAdaptiveSizePolicy                   = false                               {product}

     bool PrintCMSInitiationStatistics              = false                               {product}

     intx PrintCMSStatistics                        =                                    {product}

     bool PrintClassHistogram                       = false                               {manageable}

     bool PrintClassHistogramAfterFullGC            = false                               {manageable}

     bool PrintClassHistogramBeforeFullGC           = false                               {manageable}

     bool PrintCodeCache                            = false                               {product}

     bool PrintCodeCacheOnCompilation               = false                               {product}

     bool PrintCommandLineFlags                     = false                               {product}

     bool PrintCompilation                          = false                               {product}

     bool PrintConcurrentLocks                      = false                               {manageable}

     intx PrintFLSCensus                            =                                    {product}

     intx PrintFLSStatistics                        =                                    {product}

     bool PrintFlagsFinal                          := true                                {product}

     bool PrintFlagsInitial                         = false                               {product}

     bool PrintGC                                   = false                               {manageable}

     bool PrintGCApplicationConcurrentTime          = false                               {product}

     bool PrintGCApplicationStoppedTime             = false                               {product}

     bool PrintGCCause                              = true                                {product}

     bool PrintGCDateStamps                         = false                               {manageable}

     bool PrintGCDetails                            = false                               {manageable}

     bool PrintGCID                                 = false                               {manageable}

     bool PrintGCTaskTimeStamps                     = false                               {product}

     bool PrintGCTimeStamps                         = false                               {manageable}

     bool PrintHeapAtGC                             = false                               {product rw}

     bool PrintHeapAtGCExtended                     = false                               {product rw}

     bool PrintHeapAtSIGBREAK                       = true                                {product}

     bool PrintJNIGCStalls                          = false                               {product}

     bool PrintJNIResolving                         = false                               {product}

     bool PrintOldPLAB                              = false                               {product}

     bool PrintOopAddress                           = false                               {product}

     bool PrintPLAB                                 = false                               {product}

     bool PrintParallelOldGCPhaseTimes              = false                               {product}

     bool PrintPromotionFailure                     = false                               {product}

     bool PrintReferenceGC                          = false                               {product}

     bool PrintSafepointStatistics                  = false                               {product}

     intx PrintSafepointStatisticsCount             =                                  {product}

     intx PrintSafepointStatisticsTimeout           = -                                  {product}

     bool PrintSharedArchiveAndExit                 = false                               {product}

     bool PrintSharedDictionary                     = false                               {product}

     bool PrintSharedSpaces                         = false                               {product}

     bool PrintStringDeduplicationStatistics        = false                               {product}

     bool PrintStringTableStatistics                = false                               {product}

     bool PrintTLAB                                 = false                               {product}

     bool PrintTenuringDistribution                 = false                               {product}

     bool PrintTieredEvents                         = false                               {product}

     bool PrintVMOptions                            = false                               {product}

     bool PrintVMQWaitTime                          = false                               {product}

     bool PrintWarnings                             = true                                {product}

    uintx ProcessDistributionStride                 =                                    {product}

     bool ProfileInterpreter                        = true                                {pd product}

     bool ProfileIntervals                          = false                               {product}

     intx ProfileIntervalsTicks                     =                                  {product}

     intx ProfileMaturityPercentage                 =                                   {product}

     bool ProfileVM                                 = false                               {product}

     bool ProfilerPrintByteCodeStatistics           = false                               {product}

     bool ProfilerRecordPC                          = false                               {product}

    uintx PromotedPadding                           =                                    {product}

    uintx QueuedAllocationWarningCount              =                                    {product}

    uintx RTMRetryCount                             =                                    {ARCH product}

     bool RangeCheckElimination                     = true                                {product}

     intx ReadPrefetchInstr                         =                                    {ARCH product}

     bool ReassociateInvariants                     = true                                {C2 product}

     bool ReduceBulkZeroing                         = true                                {C2 product}

     bool ReduceFieldZeroing                        = true                                {C2 product}

     bool ReduceInitialCardMarks                    = true                                {C2 product}

     bool ReduceSignalUsage                         = false                               {product}

     intx RefDiscoveryPolicy                        =                                    {product}

     bool ReflectionWrapResolutionErrors            = true                                {product}

     bool RegisterFinalizersAtInit                  = true                                {product}

     bool RelaxAccessControlCheck                   = false                               {product}

    ccstr ReplayDataFile                            =                                     {product}

     bool RequireSharedSpaces                       = false                               {product}

    uintx ReservedCodeCacheSize                     =                            {pd product}

     bool ResizeOldPLAB                             = true                                {product}

     bool ResizePLAB                                = true                                {product}

     bool ResizeTLAB                                = true                                {pd product}

     bool RestoreMXCSROnJNICalls                    = false                               {product}

     bool RestrictContended                         = true                                {product}

     bool RewriteBytecodes                          = true                                {pd product}

     bool RewriteFrequentPairs                      = true                                {pd product}

     intx SafepointPollOffset                       =                                  {C1 pd product}

     intx SafepointSpinBeforeYield                  =                                 {product}

     bool SafepointTimeout                          = false                               {product}

     intx SafepointTimeoutDelay                     =                                {product}

     bool ScavengeBeforeFullGC                      = true                                {product}

     intx SelfDestructTimer                         =                                    {product}

    uintx SharedBaseAddress                         =                                    {product}

    ccstr SharedClassListFile                       =                                     {product}

    uintx SharedMiscCodeSize                        =                               {product}

    uintx SharedMiscDataSize                        =                              {product}

    uintx SharedReadOnlySize                        =                             {product}

    uintx SharedReadWriteSize                       =                             {product}

     bool ShowMessageBoxOnError                     = false                               {product}

     intx SoftRefLRUPolicyMSPerMB                   =                                 {product}

     bool SpecialEncodeISOArray                     = true                                {C2 product}

     bool SplitIfBlocks                             = true                                {C2 product}

     intx StackRedPages                             =                                    {pd product}

     intx StackShadowPages                          =                                    {pd product}

     bool StackTraceInThrowable                     = true                                {product}

     intx StackYellowPages                          =                                    {pd product}

     bool StartAttachListener                       = false                               {product}

     intx StarvationMonitorInterval                 =                                  {product}

     bool StressLdcRewrite                          = false                               {product}

    uintx StringDeduplicationAgeThreshold           =                                    {product}

    uintx StringTableSize                           =                                {product}

     bool SuppressFatalErrorMessage                 = false                               {product}

    uintx SurvivorPadding                           =                                    {product}

    uintx SurvivorRatio                             =                                    {product}

     intx SuspendRetryCount                         =                                   {product}

     intx SuspendRetryDelay                         =                                    {product}

     intx SyncFlags                                 =                                    {product}

    ccstr SyncKnobs                                 =                                     {product}

     intx SyncVerbose                               =                                    {product}

    uintx TLABAllocationWeight                      =                                   {product}

    uintx TLABRefillWasteFraction                   =                                   {product}

    uintx TLABSize                                  =                                    {product}

     bool TLABStats                                 = true                                {product}

    uintx TLABWasteIncrement                        =                                    {product}

    uintx TLABWasteTargetPercent                    =                                    {product}

    uintx TargetPLABWastePct                        =                                   {product}

    uintx TargetSurvivorRatio                       =                                   {product}

    uintx TenuredGenerationSizeIncrement            =                                   {product}

    uintx TenuredGenerationSizeSupplement           =                                   {product}

    uintx TenuredGenerationSizeSupplementDecay      =                                    {product}

     intx ThreadPriorityPolicy                      =                                    {product}

     bool ThreadPriorityVerbose                     = false                               {product}

    uintx ThreadSafetyMargin                        =                             {product}

     intx ThreadStackSize                           =                                    {pd product}

    uintx ThresholdTolerance                        =                                   {product}

     intx Tier0BackedgeNotifyFreqLog                =                                   {product}

     intx Tier0InvokeNotifyFreqLog                  =                                    {product}

     intx Tier0ProfilingStartPercentage             =                                  {product}

     intx Tier23InlineeNotifyFreqLog                =                                   {product}

     intx Tier2BackEdgeThreshold                    =                                    {product}

     intx Tier2BackedgeNotifyFreqLog                =                                   {product}

     intx Tier2CompileThreshold                     =                                    {product}

     intx Tier2InvokeNotifyFreqLog                  =                                   {product}

     intx Tier3BackEdgeThreshold                    =                                {product}

     intx Tier3BackedgeNotifyFreqLog                =                                   {product}

     intx Tier3CompileThreshold                     =                                 {product}

     intx Tier3DelayOff                             =                                    {product}

     intx Tier3DelayOn                              =                                    {product}

     intx Tier3InvocationThreshold                  =                                  {product}

     intx Tier3InvokeNotifyFreqLog                  =                                   {product}

     intx Tier3LoadFeedback                         =                                    {product}

     intx Tier3MinInvocationThreshold               =                                  {product}

     intx Tier4BackEdgeThreshold                    =                                {product}

     intx Tier4CompileThreshold                     =                                {product}

     intx Tier4InvocationThreshold                  =                                 {product}

     intx Tier4LoadFeedback                         =                                    {product}

     intx Tier4MinInvocationThreshold               =                                  {product}

     bool TieredCompilation                         = true                                {pd product}

     intx TieredCompileTaskTimeout                  =                                   {product}

     intx TieredRateUpdateMaxTime                   =                                   {product}

     intx TieredRateUpdateMinTime                   =                                    {product}

     intx TieredStopAtLevel                         =                                    {product}

     bool TimeLinearScan                            = false                               {C1 product}

     bool TraceBiasedLocking                        = false                               {product}

     bool TraceClassLoading                         = false                               {product rw}

     bool TraceClassLoadingPreorder                 = false                               {product}

     bool TraceClassPaths                           = false                               {product}

     bool TraceClassResolution                      = false                               {product}

     bool TraceClassUnloading                       = false                               {product rw}

     bool TraceDynamicGCThreads                     = false                               {product}

     bool TraceGen0Time                             = false                               {product}

     bool TraceGen1Time                             = false                               {product}

    ccstr TraceJVMTI                                =                                     {product}

     bool TraceLoaderConstraints                    = false                               {product rw}

     bool TraceMetadataHumongousAllocation          = false                               {product}

     bool TraceMonitorInflation                     = false                               {product}

     bool TraceParallelOldGCTasks                   = false                               {product}

     intx TraceRedefineClasses                      =                                    {product}

     bool TraceSafepointCleanupTime                 = false                               {product}

     bool TraceSharedLookupCache                    = false                               {product}

     bool TraceSuspendWaitFailures                  = false                               {product}

     intx TrackedInitializationLimit                =                                   {C2 product}

     bool TransmitErrorReport                       = false                               {product}

     bool TrapBasedNullChecks                       = false                               {pd product}

     bool TrapBasedRangeChecks                      = false                               {C2 pd product}

     intx TypeProfileArgsLimit                      =                                    {product}

    uintx TypeProfileLevel                          =                                  {pd product}

     intx TypeProfileMajorReceiverPercent           =                                   {C2 product}

     intx TypeProfileParmsLimit                     =                                    {product}

     intx TypeProfileWidth                          =                                    {product}

     intx UnguardOnExecutionViolation               =                                    {product}

     bool UnlinkSymbolsALot                         = false                               {product}

     bool Use486InstrsOnly                          = false                               {ARCH product}

     bool UseAES                                    = true                                {product}

     bool UseAESIntrinsics                          = true                                {product}

     intx UseAVX                                    =                                    {ARCH product}

     bool UseAdaptiveGCBoundary                     = false                               {product}

     bool UseAdaptiveGenerationSizePolicyAtMajorCollection  = true                                {product}

     bool UseAdaptiveGenerationSizePolicyAtMinorCollection  = true                                {product}

     bool UseAdaptiveNUMAChunkSizing                = true                                {product}

     bool UseAdaptiveSizeDecayMajorGCCost           = true                                {product}

     bool UseAdaptiveSizePolicy                     = true                                {product}

     bool UseAdaptiveSizePolicyFootprintGoal        = true                                {product}

     bool UseAdaptiveSizePolicyWithSystemGC         = false                               {product}

     bool UseAddressNop                             = true                                {ARCH product}

     bool UseAltSigs                                = false                               {product}

     bool UseAutoGCSelectPolicy                     = false                               {product}

     bool UseBMI1Instructions                       = true                                {ARCH product}

     bool UseBMI2Instructions                       = true                                {ARCH product}

     bool UseBiasedLocking                          = true                                {product}

     bool UseBimorphicInlining                      = true                                {C2 product}

     bool UseBoundThreads                           = true                                {product}

     bool UseCLMUL                                  = true                                {ARCH product}

     bool UseCMSBestFit                             = true                                {product}

     bool UseCMSCollectionPassing                   = true                                {product}

     bool UseCMSCompactAtFullCollection             = true                                {product}

     bool UseCMSInitiatingOccupancyOnly             = false                               {product}

     bool UseCRC32Intrinsics                        = true                                {product}

     bool UseCodeCacheFlushing                      = true                                {product}

     bool UseCompiler                               = true                                {product}

     bool UseCompilerSafepoints                     = true                                {product}

     bool UseCompressedClassPointers               := true                                {lp64_product}

     bool UseCompressedOops                        := true                                {lp64_product}

     bool UseConcMarkSweepGC                        = false                               {product}

     bool UseCondCardMark                           = false                               {C2 product}

     bool UseCountLeadingZerosInstruction           = true                                {ARCH product}

     bool UseCountTrailingZerosInstruction          = true                                {ARCH product}

     bool UseCountedLoopSafepoints                  = false                               {C2 product}

     bool UseCounterDecay                           = true                                {product}

     bool UseDivMod                                 = true                                {C2 product}

     bool UseDynamicNumberOfGCThreads               = false                               {product}

     bool UseFPUForSpilling                         = true                                {C2 product}

     bool UseFastAccessorMethods                    = false                               {product}

     bool UseFastEmptyMethods                       = false                               {product}

     bool UseFastJNIAccessors                       = true                                {product}

     bool UseFastStosb                              = true                                {ARCH product}

     bool UseG1GC                                   = false                               {product}

     bool UseGCLogFileRotation                      = false                               {product}

     bool UseGCOverheadLimit                        = true                                {product}

     bool UseGCTaskAffinity                         = false                               {product}

     bool UseHeavyMonitors                          = false                               {product}

     bool UseInlineCaches                           = true                                {product}

     bool UseInterpreter                            = true                                {product}

     bool UseJumpTables                             = true                                {C2 product}

     bool UseLWPSynchronization                     = true                                {product}

     bool UseLargePages                             = false                               {pd product}

     bool UseLargePagesInMetaspace                  = false                               {product}

     bool UseLargePagesIndividualAllocation        := false                               {pd product}

     bool UseLockedTracing                          = false                               {product}

     bool UseLoopCounter                            = true                                {product}

     bool UseLoopInvariantCodeMotion                = true                                {C1 product}

     bool UseLoopPredicate                          = true                                {C2 product}

     bool UseMathExactIntrinsics                    = true                                {C2 product}

     bool UseMaximumCompactionOnSystemGC            = true                                {product}

     bool UseMembar                                 = false                               {pd product}

     bool UseMontgomeryMultiplyIntrinsic            = true                                {C2 product}

     bool UseMontgomerySquareIntrinsic              = true                                {C2 product}

     bool UseMulAddIntrinsic                        = true                                {C2 product}

     bool UseMultiplyToLenIntrinsic                 = true                                {C2 product}

     bool UseNUMA                                   = false                               {product}

     bool UseNUMAInterleaving                       = false                               {product}

     bool UseNewLongLShift                          = false                               {ARCH product}

     bool UseOSErrorReporting                       = false                               {pd product}

     bool UseOldInlining                            = true                                {C2 product}

     bool UseOnStackReplacement                     = true                                {pd product}

     bool UseOnlyInlinedBimorphic                   = true                                {C2 product}

     bool UseOptoBiasInlining                       = true                                {C2 product}

     bool UsePSAdaptiveSurvivorSizePolicy           = true                                {product}

     bool UseParNewGC                               = false                               {product}

     bool UseParallelGC                            := true                                {product}

     bool UseParallelOldGC                          = true                                {product}

     bool UsePerfData                               = true                                {product}

     bool UsePopCountInstruction                    = true                                {product}

     bool UseRDPCForConstantTableBase               = false                               {C2 product}

     bool UseRTMDeopt                               = false                               {ARCH product}

     bool UseRTMLocking                             = false                               {ARCH product}

     bool UseSHA                                    = false                               {product}

     bool UseSHA1Intrinsics                         = false                               {product}

     bool UseSHA256Intrinsics                       = false                               {product}

     bool UseSHA512Intrinsics                       = false                               {product}

     intx UseSSE                                    =                                    {product}

     bool UseSSE42Intrinsics                        = true                                {product}

     bool UseSerialGC                               = false                               {product}

     bool UseSharedSpaces                           = false                               {product}

     bool UseSignalChaining                         = true                                {product}

     bool UseSquareToLenIntrinsic                   = true                                {C2 product}

     bool UseStoreImmI16                            = false                               {ARCH product}

     bool UseStringDeduplication                    = false                               {product}

     bool UseSuperWord                              = true                                {C2 product}

     bool UseTLAB                                   = true                                {pd product}

     bool UseThreadPriorities                       = true                                {pd product}

     bool UseTypeProfile                            = true                                {product}

     bool UseTypeSpeculation                        = true                                {C2 product}

     bool UseUTCFileTimestamp                       = true                                {product}

     bool UseUnalignedLoadStores                    = true                                {ARCH product}

     bool UseVMInterruptibleIO                      = false                               {product}

     bool UseXMMForArrayCopy                        = true                                {product}

     bool UseXmmI2D                                 = false                               {ARCH product}

     bool UseXmmI2F                                 = false                               {ARCH product}

     bool UseXmmLoadAndClearUpper                   = true                                {ARCH product}

     bool UseXmmRegToRegMoveAll                     = true                                {ARCH product}

     bool VMThreadHintNoPreempt                     = false                               {product}

     intx VMThreadPriority                          = -                                  {product}

     intx VMThreadStackSize                         =                                    {pd product}

     intx ValueMapInitialSize                       =                                   {C1 product}

     intx ValueMapMaxLoopSize                       =                                    {C1 product}

     intx ValueSearchLimit                          =                                 {C2 product}

     bool VerifyMergedCPBytecodes                   = true                                {product}

     bool VerifySharedSpaces                        = false                               {product}

     intx WorkAroundNPTLTimedWaitHang               =                                    {product}

    uintx YoungGenerationSizeIncrement              =                                   {product}

    uintx YoungGenerationSizeSupplement             =                                   {product}

    uintx YoungGenerationSizeSupplementDecay        =                                    {product}

    uintx YoungPLABSize                             =                                 {product}

     bool ZeroTLAB                                  = false                               {product}

     intx hashCode                                  =                                    {product}

用法: java [-options] class [args...]

           (执行类)

   或  java [-options] -jar jarfile [args...]

           (执行 jar 文件)

其中选项包括:

    -d32          使用  位数据模型 (如果可用)

    -d64          使用  位数据模型 (如果可用)

    -server       选择 "server" VM

                  默认 VM 是 server.

    -cp <目录和 zip/jar 文件的类搜索路径>

    -classpath <目录和 zip/jar 文件的类搜索路径>

                  用 ; 分隔的目录, JAR 档案

                  和 ZIP 档案列表, 用于搜索类文件。

    -D<名称>=<值>

                  设置系统属性

    -verbose:[class|gc|jni]

                  启用详细输出

    -version      输出产品版本并退出

    -version:<值>

                  警告: 此功能已过时, 将在

                  未来发行版中删除。

                  需要指定的版本才能运行

    -showversion  输出产品版本并继续

    -jre-restrict-search | -no-jre-restrict-search

                  警告: 此功能已过时, 将在

                  未来发行版中删除。

                  在版本搜索中包括/排除用户专用 JRE

    -? -help      输出此帮助消息

    -X            输出非标准选项的帮助

    -ea[:<packagename>...|:<classname>]

    -enableassertions[:<packagename>...|:<classname>]

                  按指定的粒度启用断言

    -da[:<packagename>...|:<classname>]

    -disableassertions[:<packagename>...|:<classname>]

                  禁用具有指定粒度的断言

    -esa | -enablesystemassertions

                  启用系统断言

    -dsa | -disablesystemassertions

                  禁用系统断言

    -agentlib:<libname>[=<选项>]

                  加载本机代理库 <libname>, 例如 -agentlib:hprof

                  另请参阅 -agentlib:jdwp=help 和 -agentlib:hprof=help

    -agentpath:<pathname>[=<选项>]

                  按完整路径名加载本机代理库

    -javaagent:<jarpath>[=<选项>]

                  加载 Java 编程语言代理, 请参阅 java.lang.instrument

    -splash:<imagepath>

                  使用指定的图像显示启动屏幕

有关详细信息, 请参阅 http://www.oracle.com/technetwork/java/javase/documentation/index.html。

上面的参数中有等号（=和:=），分别代表的是默认值，和被修改的值啦

好了，基础够基础了吧，以后这些加（+）减（-）等于（=或:=）看的懂了

二、基础工具

$JAVA_HOME/bin目录下真的有很多的工具，这里不截图啦，直接上用的比较的工具好啦

2.1、jps

这个工具真的很实用，而且很简单呢，功能linux的ps命令类似：可以列出正在运行的虚拟机进程，并显示虚拟机执行主类（Main Class，main()函数所在的类）名称以及这些进程的本地虚拟机唯一ID（LVMID，Local Virtual Machine Identifier）

[root@hadoop apache-tomcat-8.5.]# jps -help

usage: jps [-help]

       jps [-q] [-mlvV] [<hostid>]

Definitions:

    <hostid>:      <hostname>[:<port>]

-l : 输出主类全名或jar路径

-q : 只输出LVMID

-m : 输出JVM启动时传递给main()的参数

-v : 输出JVM启动时显示指定的JVM参数

2.2、jstat

jstat（JVM Statistics Monitoring Tool）是用于监视虚拟机各种运行状态信息的命令行工具。它可以显示本地或者远程[插图]虚拟机进程中的类加载、内存、垃圾收集、即时编译等运行时数据。

[root@hadoop apache-tomcat-8.5.]# jstat -help

Usage: jstat -help|-options

       jstat -<option> [-t] [-h<lines>] <vmid> [<interval> [<count>]]

Definitions:

  <option>      An option reported by the -options option

  <vmid>        Virtual Machine Identifier. A vmid takes the following form:

                     <lvmid>[@<hostname>[:<port>]]

                Where <lvmid> is the local vm identifier for the target

                Java virtual machine, typically a process id; <hostname> is

                the name of the host running the target Java virtual machine;

                and <port> is the port number for the rmiregistry on the

                target host. See the jvmstat documentation for a more complete

                description of the Virtual Machine Identifier.

  <lines>       Number of samples between header lines.

  <interval>    Sampling interval. The following forms are allowed:

                    <n>["ms"|"s"]

                Where <n> is an integer and the suffix specifies the units as

                milliseconds("ms") or seconds("s"). The default units are "ms".

  <count>       Number of samples to take before terminating.

  -J<flag>      Pass <flag> directly to the runtime system.

jstat -options #查看下支持的选项，如下

[root@hadoop apache-tomcat-8.5.]# jstat -options

-class  #类加载器

-compiler #JIT

-gc  #GC堆状态

-gccapacity #各个区的大小

-gccause #最近一次GC的统计和原因

-gcmetacapacity #元空间大小

-gcnew #新区统计

-gcnewcapacity #新区大小

-gcold #老区统计

-gcoldcapacity #老区大小

-gcutil #GC汇总统计

-printcompilation #HotSpot编译统计

Options #选项，我们一般使用 -gcutil 查看gc情况

vmid    #VM的进程号，即当前运行的java进程号，可以理解我java程序的pid

interval #间隔时间，单位为秒或者毫秒

count   #打印次数，如果缺省则打印无数次

对于命令格式中的VMID与LVMID需要特别说明一下：如果是本地虚拟机进程，VMID与LVMID是一致的；如果是远程虚拟机进程，那VMID的格式应当是

[protocol:][//]lvmid[@hostname][:port]/servername]

开始操作：

jstat -class 1645 #类加载的统计

Loaded：加载class的数量

Bytes：所占用空间大小

Unloaded：未加载数量

Bytes：未加载占用空间

Time：时间

jstat -gc 1645 1 3 #统计3次，每隔一秒，对gc进行统计

S0C：第一个Survivor区的大小（KB）

S1C：第二个Survivor区的大小（KB）

S0U：第一个Survivor区的使用大小（KB）

S1U：第二个Survivor区的使用大小（KB）

EC：Eden区的大小（KB）

EU：Eden区的使用大小（KB）

OC：Old区大小（KB）

OU：Old使用大小（KB）

MC：方法区大小（KB），java8方法区的实现是元数据空间，java7的方法区实现是永久代

MU：方法区使用大小（KB）

CCSC：压缩类空间大小（KB）

CCSU：压缩类空间使用大小（KB）

YGC：年轻代垃圾回收次数

YGCT：年轻代垃圾回收消耗时间

FGC：老年代垃圾回收次数

FGCT：老年代垃圾回收消耗时间

GCT：垃圾回收消耗总时间

jstat -compiler 1645 #对编译进行统计

Compiled：编译数量。

Failed：失败数量

Invalid：不可用数量

Time：时间

FailedType：失败类型

FailedMethod：失败的方法

2.3、jinfo

jinfo（Configuration Info for Java）的作用是实时查看和调整虚拟机各项参数

[root@hadoop ~]# jinfo -help

Usage:

    jinfo [option] <pid>

        (to connect to running process)

    jinfo [option] <executable <core>

        (to connect to a core file)

    jinfo [option] [server_id@]<remote server IP or hostname>

        (to connect to remote debug server)

where <option> is one of:

    -flag <name>         to print the value of the named VM flag #打印单个jvm的参数

    -flag [+|-]<name>    to enable or disable the named VM flag #运行期修改一部分运行期可写的虚拟机参数值

    -flag <name>=<value> to set the named VM flag to the given value #运行期修改一部分运行期可写的虚拟机参数值

    -flags               to print VM flags #打印该进程的相关的参数

    -sysprops            to print Java system properties #把虚拟机进程的System.getProperties()的内容打印出来

    <no option>          to print both of the above

    -h | -help           to print this help message

jinfo -flags 1645

jinfo -flag InitialHeapSize 1645

[root@hadoop ~]# jinfo -sysprops

Attaching to process ID , please wait...

Debugger attached successfully.

Server compiler detected.

JVM version is 25.181-b13

java.runtime.name = Java(TM) SE Runtime Environment

java.vm.version = 25.181-b13

sun.boot.library.path = /home/hadoop/jdk/jre/lib/amd64

java.protocol.handler.pkgs = org.apache.catalina.webresources

shared.loader =

java.vendor.url = http://java.oracle.com/

java.vm.vendor = Oracle Corporation

path.separator = :

file.encoding.pkg = sun.io

java.vm.name = Java HotSpot(TM) -Bit Server VM

java.util.logging.config.file = /root/apache-tomcat-8.5./conf/logging.properties

tomcat.util.buf.StringCache.byte.enabled = true

sun.os.patch.level = unknown

sun.java.launcher = SUN_STANDARD

user.country = US

tomcat.util.scan.StandardJarScanFilter.jarsToScan = log4j-taglib*.jar,log4j-web*.jar,log4javascript*.jar,slf4j-taglib*.jar

user.dir = /root/apache-tomcat-8.5.

java.vm.specification.name = Java Virtual Machine Specification

java.runtime.version = 1.8.0_181-b13

java.awt.graphicsenv = sun.awt.X11GraphicsEnvironment

os.arch = amd64

java.endorsed.dirs = /home/hadoop/jdk/jre/lib/endorsed

line.separator =

java.io.tmpdir = /root/apache-tomcat-8.5./temp

java.vm.specification.vendor = Oracle Corporation

java.util.logging.manager = org.apache.juli.ClassLoaderLogManager

java.naming.factory.url.pkgs = org.apache.naming

os.name = Linux

org.apache.catalina.security.SecurityListener.UMASK =

sun.jnu.encoding = UTF-

ignore.endorsed.dirs =

java.library.path = /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib

java.class.version = 52.0

java.specification.name = Java Platform API Specification

sun.management.compiler = HotSpot -Bit Tiered Compilers

os.version = 2.6.-754.24..el6.x86_64

java.util.concurrent.ForkJoinPool.common.threadFactory = org.apache.catalina.startup.SafeForkJoinWorkerThreadFactory

user.home = /root

user.timezone = Asia/Chongqing

catalina.useNaming = true

java.awt.printerjob = sun.print.PSPrinterJob

file.encoding = UTF-

java.specification.version = 1.8

tomcat.util.scan.StandardJarScanFilter.jarsToSkip = annotations-api.jar,ant-junit*.jar,ant-launcher.jar,ant.jar,asm-*.jar,aspectj*.jar,bootstrap.jar,catalina-ant.jar,catalina-ha.jar,catalina-jmx-remote.jar,catalina-storeconfig.jar,catalina-tribes.jar,catalina-ws.jar,catalina.jar,cglib-*.jar,cobertura-*.jar,commons-beanutils*.jar,commons-codec*.jar,commons-collections*.jar,commons-daemon.jar,commons-dbcp*.jar,commons-digester*.jar,commons-fileupload*.jar,commons-httpclient*.jar,commons-io*.jar,commons-lang*.jar,commons-logging*.jar,commons-math*.jar,commons-pool*.jar,dom4j-*.jar,easymock-*.jar,ecj-*.jar,el-api.jar,geronimo-spec-jaxrpc*.jar,h2*.jar,hamcrest-*.jar,hibernate*.jar,httpclient*.jar,icu4j-*.jar,jasper-el.jar,jasper.jar,jaspic-api.jar,jaxb-*.jar,jaxen-*.jar,jdom-*.jar,jetty-*.jar,jmx-tools.jar,jmx.jar,jsp-api.jar,jstl.jar,jta*.jar,junit-*.jar,junit.jar,log4j*.jar,mail*.jar,objenesis-*.jar,oraclepki.jar,oro-*.jar,servlet-api-*.jar,servlet-api.jar,slf4j*.jar,taglibs-standard-spec-*.jar,tagsoup-*.jar,tomcat-api.jar,tomcat-coyote.jar,tomcat-dbcp.jar,tomcat-i18n-*.jar,tomcat-jdbc.jar,tomcat-jni.jar,tomcat-juli-adapters.jar,tomcat-juli.jar,tomcat-util-scan.jar,tomcat-util.jar,tomcat-websocket.jar,tools.jar,websocket-api.jar,wsdl4j*.jar,xercesImpl.jar,xml-apis.jar,xmlParserAPIs-*.jar,xmlParserAPIs.jar,xom-*.jar

catalina.home = /root/apache-tomcat-8.5.

user.name = root

java.class.path = /root/apache-tomcat-8.5./bin/bootstrap.jar:/root/apache-tomcat-8.5./bin/tomcat-juli.jar

java.naming.factory.initial = org.apache.naming.java.javaURLContextFactory

package.definition = sun.,java.,org.apache.catalina.,org.apache.coyote.,org.apache.jasper.,org.apache.naming.,org.apache.tomcat.

java.vm.specification.version = 1.8

sun.arch.data.model =

sun.java.command = org.apache.catalina.startup.Bootstrap start

java.home = /home/hadoop/jdk/jre

user.language = en

java.specification.vendor = Oracle Corporation

awt.toolkit = sun.awt.X11.XToolkit

java.vm.info = mixed mode

java.version = 1.8.0_181

java.ext.dirs = /home/hadoop/jdk/jre/lib/ext:/usr/java/packages/lib/ext

sun.boot.class.path = /home/hadoop/jdk/jre/lib/resources.jar:/home/hadoop/jdk/jre/lib/rt.jar:/home/hadoop/jdk/jre/lib/sunrsasign.jar:/home/hadoop/jdk/jre/lib/jsse.jar:/home/hadoop/jdk/jre/lib/jce.jar:/home/hadoop/jdk/jre/lib/charsets.jar:/home/hadoop/jdk/jre/lib/jfr.jar:/home/hadoop/jdk/jre/classes

server.loader =

java.vendor = Oracle Corporation

catalina.base = /root/apache-tomcat-8.5.

jdk.tls.ephemeralDHKeySize =

file.separator = /

java.vendor.url.bug = http://bugreport.sun.com/bugreport/

common.loader = "${catalina.base}/lib","${catalina.base}/lib/*.jar","${catalina.home}/lib","${catalina.home}/lib/*.jar"

sun.io.unicode.encoding = UnicodeLittle

sun.cpu.endian = little

package.access = sun.,org.apache.catalina.,org.apache.coyote.,org.apache.jasper.,org.apache.tomcat.

sun.cpu.isalist =

2.4、jmap

jmap（Memory Map for Java）命令用于生成堆转储快照（一般称为heapdump或dump文件），还可以使用“暴力”方式：-XX：+HeapDumpOnOutOfMemoryError参数，可以让虚拟机在内存溢出异常出现之后自动生成堆转储快照文件

jmap的作用并不仅仅是为了获取堆转储快照，它还可以查询finalize执行队列、Java堆和方法区的详细信息，如空间使用率、当前用的是哪种收集器等

[root@hadoop ~]# jmap -help

Usage:

    jmap [option] <pid>

        (to connect to running process)

    jmap [option] <executable <core>

        (to connect to a core file)

    jmap [option] [server_id@]<remote server IP or hostname>

        (to connect to remote debug server)

where <option> is one of:

    <none>               to print same info as Solaris pmap

    -heap                to print java heap summary #统计堆

    -histo[:live]        to print histogram of java object heap; if the "live"

                         suboption is specified, only count live objects

    -clstats             to print class loader statistics

    -finalizerinfo       to print information on objects awaiting finalization

    -dump:<dump-options> to dump java heap in hprof binary format #dump出java堆的二进制文件

                         dump-options:

                           live         dump only live objects; if not specified,

                                        all objects in the heap are dumped.

                           format=b     binary format

                           file=<file>  dump heap to <file>

                         Example: jmap -dump:live,format=b,file=heap.bin <pid>

    -F                   force. Use with -dump:<dump-options> <pid> or -histo

                         to force a heap dump or histogram when <pid> does not

                         respond. The "live" suboption is not supported

                         in this mode.

    -h | -help           to print this help message

    -J<flag>             to pass <flag> directly to the runtime system

-heap #打印jvm heap的情况，比如参数，分代，回收器等

-histo #打印jvm heap的直方图。其输出信息包括类名，对象数量，对象占用大小。

-histo:live #同上，但是只答应存活对象的情况

-dump #生成堆转储快照,格式为-dump:[live,]format=b,file=<filename>,其中自参数说明是否只dump出存活对象

-finalizerinfo #显示在F-Queue中等待的finalizer线程执行finalize方法的对象

-clstats #打印类的加载信息

-F #强制生成dump文件

jmap -heap 1645

jmap -histo 1645 | more #查看内存中的对象和数量

上图中的对象说明：

B byte

C char

D double

F float

I int

J long

Z boolean

[ 数组，如[I表示int[]

[L+类名 其他对象

jmap -dump:format=b,file=/root/dump.bin 1645  #将内存的使用情况dump到文件中

[root@hadoop bin]# jmap -dump:format=b,file=/root/dump.bin

Dumping heap to /root/dump.bin ...

Heap dump file created

2.5、jhat

JDK提供jhat（JVM Heap Analysis Tool）命令与jmap搭配使用，来分析jmap生成的堆转储快照。jhat内置了一个微型的HTTP/Web服务器，生成堆转储快照的分析结果后，可以在浏览器中查看（实际情况使用的不多）

[root@hadoop ~]# jhat -help

Usage:  jhat [-stack <bool>] [-refs <bool>] [-port <port>] [-baseline <file>] [-debug <int>] [-version] [-h|-help] <file>

        -J<flag>          Pass <flag> directly to the runtime system. For

                          example, -J-mx512m to use a maximum heap size of 512MB

        -stack false:     Turn off tracking object allocation call stack.

        -refs false:      Turn off tracking of references to objects

        -port <port>:     Set the port for the HTTP server.  Defaults to

        -exclude <file>:  Specify a file that lists data members that should

                          be excluded from the reachableFrom query.

        -baseline <file>: Specify a baseline object dump.  Objects in

                          both heap dumps with the same ID and same class will

                          be marked as not being "new".

        -debug <int>:     Set debug level.

                            :  No debug output

                            :  Debug hprof file parsing

                            :  Debug hprof file parsing, no server

        -version          Report version number

        -h|-help          Print this help and exit

        <file>            The file to read

For a dump file that contains multiple heap dumps,

you may specify which dump in the file

by appending "#<number>" to the file name, i.e. "foo.hprof#3".

All boolean options default to "true"

jhat -port 9999 dump.bin

登录自己的地址：http://192.168.88.137:9999/

这个网址拉到最下面有一个查询功能：

如上的每一个结果都可以点进去去查看

2.6、jstack

jstack（Stack Trace for Java）命令用于生成虚拟机当前时刻的线程快照（一般称为threaddump或者javacore文件）。线程快照就是当前虚拟机内每一条线程正在执行的方法堆栈的集合，生成线程快照的目的通常是定位线程出现长时间停顿的原因，如线程间死锁、死循环、请求外部资源导致的长时间挂起等，都是导致线程长时间停顿的常见原因

[root@hadoop ~]# jstack -help

Usage:

    jstack [-l] <pid>

        (to connect to running process)

    jstack -F [-m] [-l] <pid>

        (to connect to a hung process)

    jstack [-m] [-l] <executable> <core>

        (to connect to a core file)

    jstack [-m] [-l] [server_id@]<remote server IP or hostname>

        (to connect to a remote debug server)

Options:

    -F  to force a thread dump. Use when jstack <pid> does not respond (process is hung)

    -m  to print both java and native frames (mixed mode)

    -l  long listing. Prints additional information about locks

    -h or -help to print this help message

-F : 当正常输出请求不被响应时，强制输出线程堆栈

-l : 除堆栈外，显示关于锁的附加信息

-m : 如果调用到本地方法的话，可以显示C/C++的堆栈

jstack 1645 | more #查看该线程的快照信息

如上的状态信息可以参考：java多线程与并发（基础篇）

三、可视化工具

3.1、JConsole

JConsole（Java Monitoring and Management Console）是一款基于JMX（Java Manage-ment Extensions）的可视化监视、管理工具。它的主要功能是通过JMX的MBean（Managed Bean）对系统进行信息收集和参数动态调整

一、本地连接

可以看出来可以对内存，线程等进行监控。

二、远程监控

这里我们使用tomcat做实验，首先要修改catalina.sh文件，添加如下内容：参考https://blog.csdn.net/shamoshuizu/article/details/70598268

JAVA_OPTS="-Djava.rmi.server.hostname=192.168.88.137 -Dcom.sun.management.jmxremote.port=8099 -Dcom.sun.management.jmxremote.rmi.port=8099 -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.authenticate=false"

然后重启tomcat，接下来连接远程

这个工具使用起来并不难，只要自己要有jvm的基础啦，不然看不懂，展示出来了也是白干活。

3.2、VisualVM

VisualVM（All-in-One Java Troubleshooting Tool）是功能最强大的运行监视和故障处理程序之一，能够监控线程，内存情况，查看方法的CPU时间和内存中的对象，已被GC的对象，反向查看分配的堆栈，使用起来也很简单

双击jvisualvm.exe软件，打开该工具

同JConsole 一样可以本地和远程，直接打开本地进程

基本pid，jvm参数，主机等一览无余，还有监控页面包括cpu，堆，类，线程等监控，还可以执行垃圾回收，和dump线程呢

试试远程的，同JConsole 的设置方式对tomcate进行设置

其实工具是什么呢，就是为了方便获取信息嘛，能不能看懂，能不能还得看自己的水平够不够，能不能够发现问题，能不能解决问题了。

3.3、JMC

Java Mission Control：可持续在线的监控工具

JMC与虚拟机之间同样采取JMX协议进行通信，JMC一方面作为JMX控制台，显示来自虚拟机MBean提供的数据；另一方面作为JFR的分析工具，展示来自JFR的数据

用起来也很简单，双击jmc.exe打开工具，默认情况下会扫描出本地的进程，然后可以点击：文件->连接，来创建新的连接：

然后根据下图操作，遇到情况下一步，下一步就好，就有如下的图了：

该工具持续监控了很多东西：

一般信息：关于虚拟机、操作系统和记录的一般信息。
内存：关于内存管理和垃圾收集的信息。
代码：关于方法、异常错误、编译和类加载的信息。
线程：关于应用程序中线程和锁的信息。
I/O：关于文件和套接字输入、输出的信息。
系统：关于正在运行Java虚拟机的系统、进程和环境变量的信息。
事件：关于记录中的事件类型的信息，可以根据线程或堆栈跟踪，按照日志或图形的格式查看。

四、其他工具-MAT

MAT(Memory Analyzer Tool)，一个基于Eclipse的内存分析工具，是一个快速、功能丰富的JAVA heap分析工具，它可以帮助我们查找内存泄漏和减少内存消耗。使用内存分析工具从众多的对象中进行分析，快速的计算出在内存中对象的占用大小，看看是谁阻止了垃圾收集器的回收工作，并可以通过报表直观的查看到可能造成这种结果的对象

官网：https://www.eclipse.org/mat/

下载地址：https://www.eclipse.org/mat/downloads.php

下载后，解压，双击MemoryAnalyzer.exe打开程序，然后点击文件->打开dump出的文件，就出现了如下的图

下图可以看到基本的内存可能出问题的地方：

这篇文章纯粹是一个工具的使用简单说明，没有太多的技术含量，但是我觉得工欲善其事必先利其器，所以用好一些工具对自己能力的提升，效率的提升有莫大的帮助，工具这些东西只有用到的时候才会查找，但是也要大概了解下怎么用吧，比如什么工具可以用来干嘛呢，我写这个的目的就是用来以后自己当做工具文档来查看下，技术用时方恨少，所以平时多积累些也不是一件坏事呢，好吧，好好努力撒。

巴特西