Hotspot JVM 参数总结
我对JavaHotspot
VM的部分翻译，有些在工作中完全没有用到的参数我没有做解释,原文章在这
JavaHotSpotVMOptions
同时，在工作中有一些没有接触到的参数,我不打清楚其含义跟作用,也请了解的朋友留言赐教.这些Option我贴在了文章最后面.
JVM选项不严格的被分为三类：
1.Behavioraloptions，用以改变VM的基本行为.
2.Performancetuningoptions,影响VM的重要参数,对其进行调整进行性能调优.
3.DebugOptions，用来在log中进行跟踪,打印一些VM信息.
可管理标记的使用:
1.BooleanOptions:
-XX:+表示打开
-XX:-表示关闭
2.Numericoptions
-XX:=.数字需包括'm'or'M'代表单位megabytes,'k'or'K'代表单位kilobytes,'g'or'G'代表单位gigabytes，例如forexample,32k
与32768代表同一值32x1024.
3.Stringoptions
-XX:=,通常用来声明logpath.
罗列一些常用参数极其代表含义:
BehavioralOptions
-XX:-DisableExplicitGC
关闭调用System.gc()方法,但是JVM还是会在需要的时候进行fullGC.
-XX:+ScavengeBeforeFullGC
在MajorGC之前进行一次MinorGC
-XX:-UseConcMarkSweepGC
对TenuredGeneration使用CMS(concurrentmark-sweepcollection)算法.
-XX:-UseParallelGC
YoungGeneration使用Parallel算法,TenuredGeneration使用Serial算法.
-XX:-UseParallelOldGC
在FullGC中使用ParallelGC算法
-XX:-UseSerialGC
使用YoungOld带均使用Serial算法
PerformanceOptions
-XX:LargePageSizeInBytes=size
为javaheap设置pagesize
-XX:MinHeapFreeRatio=40
在GC之后最小的空闲heap占总heap的比例MinimumpercentageofheapfreeafterGCtoavoidexpansion.
-XX:MaxHeapFreeRatio=70
设置在GC之后,最大的空闲heap占总heap的比例
-XX:MaxNewSize=size
设置NewGeneration最大值.
-XX:MaxPermSize=size
设置PermGeneration的大小.
-XX:NewRatio=n
n=new/oldgenerationsizes
-XX:NewSize=2.125m
newgeneration的默认值
-XX:TargetSurvivorRatio=50
回收后survior区的期望比例
DebuggingOptions
-XX:HeapDumpPath=
设置HeapDum存储路径
-XX:-HeapDumpOnOutOfMemoryError
在OOM时生成heapdump文件.
-XX:OnOutOfMemoryError=";
用户自定义命令,在OutOfMemoryError抛出时运行定义命令.
-XX:-PrintGC
打印GC时的信息
-XX:-PrintGCDetails
打印GC时的详细信息
-XX:-PrintGCTimeStamps
打印GC的时间戳
-XX:-PrintTenuringDistribution
打印Tenured区的信息
-XX:ParallelGCThreads=
设置ParallelGarbageCollector的thread数量
-XX:MaxTenuringThreshold=
设置控制对象从新生代转移到到旧生代的MinorGC次数
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[
-XX:-TraceClassLoadingTraceloadingofclasses.
-XX:-TraceClassLoadingPreorderTraceallclassesloadedinorder
referenced(notloaded).(Introducedin1.4.2.XX:-TraceClassResolution
Traceconstantpoolresolutions.(Introducedin1.4.2.)
-XX:-TraceClassUnloading
Traceunloadingofclasses.
-XX:-TraceLoaderConstraints
Tracerecordingofloaderconstraints.(Introducedin6.)
-XX:+PerfSaveDataToFile
Savesjvmstatbinarydataonexit.
-XX:+UseCompressedOops
Enablestheuseofcompressedpointers(objectreferencesrepresentedas
32bitoffsetsinsteadof64-bitpointers)foroptimized64-bit
performancewithJavaheapsizeslessthan32gb.
-XX:+AlwaysPreTouch
Pre-touchtheJavaheapduringJVMinitialization.Everypageofthe
heapisthusdemand-zeroedduringinitializationratherthan
incrementallyduringapplicationexecution.
-XX:AllocatePrefetchDistance=
Setstheprefetchdistanceforobjectallocation.Memoryabouttobe
writtenwiththevalueofnewobjectsisprefetchedintocacheatthis
distance(inbytes)beyondtheaddressofthelastallocatedobject.
EachJavathreadhasitsownallocationpoint.Thedefaultvaluevaries
withtheplatformonwhichtheJVMisrunning.
-XX:InlineSmallCode=I
Inlineapreviouslycompiledmethodonlyifitsgeneratednativecode
sizeislessthanthis.Thedefaultvaluevarieswiththeplatformon
whichtheJVMisrunning.
-XX:MaxInlineSize=35
Maximumbytecodesizeofamethodtobeinlined.
-XX:FreqInlineSize=
Maximumbytecodesizeofafrequentlyexecutedmethodtobeinlined.ThedefaultvaluevarieswiththeplatformonwhichtheJVMisrunning.
-XX:LoopUnrollLimit=
Unrollloopbodieswithservercompilerintermediaterepresentationnodecountlessthanthisvalue.Thelimitusedbytheservercompilerisafunctionofthisvalue,nottheactualvalue.ThedefaultvaluevarieswiththeplatformonwhichtheJVMisrunning.
-XX:InitialTenuringThreshold=7
SetstheinitialtenuringthresholdforuseinadaptiveGCsizingintheparallelyoungcollector.Thetenuringthresholdisthenumberoftimesanobjectsurvivesayoungcollectionbeforebeingpromotedtotheold,ortenured,generation.
-XX:-PrintClassHistogram
PrintahistogramofclassinstancesonCtrl-Break.Manageable.
(Introducedin1.4.2.)Thejmap-histocommandprovidesequivalent
functionality.
-XX:-PrintConcurrentLocks
Printjava.util.concurrentlocksinCtrl-Breakthreaddump.Manageable.
(Introducedin6.)Thejstack-lcommandprovidesequivalent
functionality.
-XX:-PrintCommandLineFlags
Printflagsthatappearedonthecommandline.(Introducedin5.0.)
-XX:-PrintCompilation
Printmessagewhenamethodiscompiled.
]