分类： Java
2010-07-08 18:02:11
（JDK版本6.0）
SUN的JDK版本从1.3.1开始使用HotSpot虚拟机技术。
HotSpot是较新的Java虚拟机技术，用来代替JIT（Just in Time）技术，可以大大提高Java运行的性能。
Java原先是把源代码编译为字节码在虚拟机执行，这样执行速度较慢。而该技术将常用的部分代码编译为本地（原生，native）代码，这样
显著提高了性能。
用于服务器版和标准版的HotSpot有所不同。
其他的Java虚拟机也有类似的技术。
HotSpot JVM 参数可以分为标准参数（standard options）和非标准参数（non-standard options）。
标准参数相对稳定，在JDK未来的版本里不会有太大的改动。
非标准参数则有因升级JDK而改变的可能。
标准参数：
-client
使用Java HotSpot 客户端版VM。
-server
使用Java HotSpot 服务器版VM。如果是64位的JDK，默认只有server版，所以以上两个参数对64位版本JDK无效。
-agentlib: libname [=options]
加载本地代理函数库, e.g.
-agentlib:jdwp=help
-agentpath :pathname [=options]
使用给定的路径加载本地代理库。
-classpath classpath
-cp classpath
不用说了。
-Dproperty =value
设置一个系统属性。
-d32
-d64
要求程序在32位或64位下跑，未来这个参数可能有变。
-enableassertions [:
-ea [:
开启断言。
-disableassertions [:
-da [:
关闭断言。
-enablesystemassertions
- esa
启动所有系统类的断言。
-disablesystemassertions
-dsa
关闭所有系统类的断言。
-jar
这个也没什么说的。
-javaagent :jarpath [=options]
加载Java 程序语言代理
-verbose:class
输出每个加载的类详细信息。
-verbose:gc
输出GC的详细信息。
-verbose:jni
输出本地方法接口的调用信息。
-version
-help
-?
不用说了。
-X
显示可用的非标准参数
非标准参数：
-Xint
以解释模式运行。JVM不会使用HotSpot的新特性，不会将部分常用代码编译为本地代码，所有代码都以字节码的方式解释运行。你可以理解为使用JDK1.3.1以前的JIT方式运行程序。
-Xbatch
不使用后台编译。
-Xbootclasspath:bootclasspath
使用bootstrap classloader 加载指定路径的class或jar，这是种完全覆盖默认系统类加载的方案，慎用。
-Xbootclasspath/a:bootclasspath
将指定的classpath追加到默认的bootclasspath的后面加载
-Xbootclasspath/p:bootclasspath
将指定的classpath追加到默认的bootclasspath的前面加载
-Xcheck:jni
在调用JNI函数时做额外的检查。这个参数会降低JVM的执行性能。
-Xfuture
执行严格的class文件格式检查，不加这个参数，默认使用JDK1.1.* 版本的class格式检查方法。
-Xnoclassgc
禁用class垃圾收集。
-Xincgc
开启增量垃圾收集机制。默认为关闭。增量垃圾收集能减少因垃圾收集而引起的程序中断，它会在程序运行期间不定期地以并发的方式运行，在运行期间不会引起中断但是会减少分配给程序的cpu资源。
-Xloggc:file
GC详情日志。效果如-verbose:gc ，不过这个可以输出到一个文件。除了-verbose:gc包含的信息，还有显示发生的时间。 文件可以是远程的，但是考虑到网络延迟会引起JVM中断，一般建议使用本地文件，
-Xms
分配的堆空间初始值：
-Xms6291456
-Xms6144k
-Xms6m
-Xmx
分配的堆空间最大值：
-Xmx83886080
-Xmx81920k
-Xmx80m
-Xprof
在运行程序时给出分析数据。适用于开发环境，不适用于生产环境。
-Xrs
减少JVM的操作系统信号的使用量。
-Xss
线程栈内存。
非标准-XX参数
有三种-XX参数的形式：
以下是-XX参数列表，本来想都翻译过来，但是发现一些技术术语如果硬是翻译可能会导致词不达意，因此大部分描述都保持原文。
| 参数名和默认值 |
描述 |
|---|---|
| -XX:-AllowUserSignalHandlers | 允许使用用户自定义的信号处理器 (只对应Solaris和Linux) |
| -XX:AltStackSize=16384 | 修改栈容量 (单位 Kb) (对应Solaris, JDK 5.0以后弃用) |
| -XX:-DisableExplicitGC | 禁止手动调用System.gc() |
| -XX:+FailOverToOldVerifier | 如果新的类型校验器验证失败使用旧版本的类型校验器 (开始于JDK6.) |
| -XX:+HandlePromotionFailure | The youngest generation collection does not require a guarantee of full promotion of all live objects. (Introduced in 1.4.2 update 11) [5.0 and earlier: false.] |
| -XX:+MaxFDLimit | 将文件描述符加到最大 (对应Solaris) |
| -XX:PreBlockSpin=10 | Spin count variable for use with -XX:+UseSpinning. Controls the maximum spin iterations allowed before entering operating system thread synchronization code. (Introduced in 1.4.2.) |
| -XX:-RelaxAccessControlCheck | 放宽类型校验机的准入控制(JDK6) |
| -XX:+ScavengeBeforeFullGC | 在full GC之前先做年轻代GC (开始于JDK1.4.1.) |
| -XX:+UseAltSigs | Use alternate signals instead of SIGUSR1 and SIGUSR2 for VM internal signals. (Introduced in 1.3.1 update 9, 1.4.1. Relevant to Solaris only.) |
| -XX:+UseBoundThreads | Bind user level threads to kernel threads. (Relevant to Solaris only.) |
| -XX:-UseConcMarkSweepGC | 使用并发的mark-sweep GC收集年老代 (始于JDK1.4.1) |
| -XX:+UseGCOverheadLimit | 使用一种限制VM做GC操作的时间所占比例过高的策略 (始于JDK6.) |
| -XX:+UseLWPSynchronization | 使用轻量级进程同步替代线程同步 (始于JDK1.4.0. Solaris相关) |
| -XX:-UseParallelGC | 使用并发平行GC(始于JDK1.4.1) |
| -XX:-UseParallelOldGC | 使用并发平行GC做 full GC. (始于JDK5.0 update 6.) |
| -XX:-UseSerialGC | 使用串行GC (始于JDK5.0.) |
| -XX:-UseSpinning | Enable naive spinning on Java monitor before entering operating system thread synchronizaton code. (Relevant to 1.4.2 and 5.0 only.) [1.4.2, multi-processor Windows platforms: true] |
| -XX:+UseTLAB | Use thread-local object allocation (Introduced in 1.4.0, known as UseTLE prior to that.) [1.4.2 and earlier, x86 or with -client: false] |
| -XX:+UseSplitVerifier | Use the new type checker with StackMapTable attributes. (Introduced in 5.0.)[5.0: false] |
| -XX:+UseThreadPriorities | Use native thread priorities. |
| -XX:+UseVMInterruptibleIO | Thread interrupt before or with EINTR for I/O operations results in OS_INTRPT. (Introduced in 6. Relevant to Solaris only.) |
| 参数名和默认值 | 描述 |
|---|---|
| -XX:+AggressiveOpts | Turn on point performance compiler optimizations that are expected to be default in upcoming releases. (Introduced in 5.0 update 6.) |
| -XX:CompileThreshold=10000 | Number of method invocations/branches before compiling [-client: 1,500] |
| -XX:LargePageSizeInBytes=4m | Sets the large page size used for the Java heap. (Introduced in 1.4.0 update 1.) [amd64: 2m.] |
| -XX:MaxHeapFreeRatio=70 | Maximum percentage of heap free after GC to avoid shrinking. |
| -XX:MaxNewSize=size | Maximum size of new generation (in bytes). Since 1.4, MaxNewSize is computed as a function of NewRatio. [1.3.1 Sparc: 32m; 1.3.1 x86: 2.5m.] |
| -XX:MaxPermSize=64m | Size of the Permanent Generation. [5.0 and newer: 64 bit VMs are scaled 30% larger; 1.4 amd64: 96m; 1.3.1 -client: 32m.] |
| -XX:MinHeapFreeRatio=40 | Minimum percentage of heap free after GC to avoid expansion. |
| -XX:NewRatio=2 | Ratio of new/old generation sizes. [Sparc -client: 8; x86 -server: 8; x86 -client: 12.]-client: 4 (1.3) 8 (1.3.1+), x86: 12] |
| -XX:NewSize=2.125m | Default size of new generation (in bytes) [5.0 and newer: 64 bit VMs are scaled 30% larger; x86: 1m; x86, 5.0 and older: 640k] |
| -XX:ReservedCodeCacheSize=32m | Reserved code cache size (in bytes) - maximum code cache size. [Solaris 64-bit, amd64, and -server x86: 48m; in 1.5.0_06 and earlier, Solaris 64-bit and and64: 1024m.] |
| -XX:SurvivorRatio=8 | Ratio of eden/survivor space size [Solaris amd64: 6; Sparc in 1.3.1: 25; other Solaris platforms in 5.0 and earlier: 32] |
| -XX:TargetSurvivorRatio=50 | Desired percentage of survivor space used after scavenge. |
| -XX:ThreadStackSize=512 | Thread Stack Size (in Kbytes). (0 means use default stack size) [Sparc: 512; Solaris x86: 320 (was 256 prior in 5.0 and earlier); Sparc 64 bit: 1024; Linux amd64: 1024 (was 0 in 5.0 and earlier); all others 0.] |
| -XX:+UseBiasedLocking | Enable biased locking. For more details, see this . (Introduced in 5.0 update 6.) [5.0: false] |
| -XX:+UseFastAccessorMethods | Use optimized versions of Get |
| -XX:-UseISM | Use Intimate Shared Memory. [Not accepted for non-Solaris platforms.] For details, see . |
| -XX:+UseLargePages | Use large page memory. (Introduced in 5.0 update 5.) For details, see . |
| -XX:+UseMPSS | Use Multiple Page Size Support w/4mb pages for the heap. Do not use with ISM as this replaces the need for ISM. (Introduced in 1.4.0 update 1, Relevant to Solaris 9 and newer.) [1.4.1 and earlier: false] |
| -XX:+StringCache | Enables caching of commonly allocated strings. |
| -XX:AllocatePrefetchLines=1 | Number of cache lines to load after the last object allocation using prefetch instructions generated in JIT compiled code. Default values are 1 if the last allocated object was an instance and 3 if it was an array. |
| -XX:AllocatePrefetchStyle=1 | Generated code style for prefetch instructions. 0 - no prefetch instructions are generate*d*, 1 - execute prefetch instructions after each allocation, 2 - use TLAB allocation watermark pointer to gate when prefetch instructions are executed. |
| 参数名和默认值 | 描述 |
|---|---|
| -XX:-CITime | Prints time spent in JIT Compiler. (Introduced in 1.4.0.) |
| -XX:ErrorFile=./hs_err_pid |
If an error occurs, save the error data to this file. (Introduced in 6.) |
| -XX:-ExtendedDTraceProbes | Enable performance-impacting probes. (Introduced in 6. Relevant to Solaris only.) |
| -XX:HeapDumpPath=./java_pid |
Path to directory or filename for heap dump. Manageable . (Introduced in 1.4.2 update 12, 5.0 update 7.) |
| -XX:-HeapDumpOnOutOfMemoryError | Dump heap to file when java.lang.OutOfMemoryError is thrown. Manageable . (Introduced in 1.4.2 update 12, 5.0 update 7.) |
| -XX:OnError=" |
Run user-defined commands on fatal error. (Introduced in 1.4.2 update 9.) |
| -XX:OnOutOfMemoryError=" |
Run user-defined commands when an OutOfMemoryError is first thrown. (Introduced in 1.4.2 update 12, 6) |
| -XX:-PrintClassHistogram | Print a histogram of class instances on Ctrl-Break. Manageable . (Introduced in 1.4.2.) The command provides equivalent functionality. |
| -XX:-PrintConcurrentLocks | Print java.util.concurrent locks in Ctrl-Break thread dump. Manageable . (Introduced in 6.) The command provides equivalent functionality. |
| -XX:-PrintCommandLineFlags | Print flags that appeared on the command line. (Introduced in 5.0.) |
| -XX:-PrintCompilation | Print message when a method is compiled. |
| -XX:-PrintGC | Print messages at garbage collection. Manageable . |
| -XX:-PrintGCDetails | Print more details at garbage collection. Manageable . (Introduced in 1.4.0.) |
| -XX:-PrintGCTimeStamps | Print timestamps at garbage collection. Manageable (Introduced in 1.4.0.) |
| -XX:-PrintTenuringDistribution | Print tenuring age information. |
| -XX:-TraceClassLoading | Trace loading of classes. |
| -XX:-TraceClassLoadingPreorder | Trace all classes loaded in order referenced (not loaded). (Introduced in 1.4.2.) |
| -XX:-TraceClassResolution | Trace constant pool resolutions. (Introduced in 1.4.2.) |
| -XX:-TraceClassUnloading | Trace unloading of classes. |
| -XX:-TraceLoaderConstraints | Trace recording of loader constraints. (Introduced in 6.) |
| -XX:+PerfSaveDataToFile | Saves jvmstat binary data on exit. |
参考：
