Java 5 版本以上（SUN JVM）GC参数化调整大全

今天终于有所斩获，发现了Sun Hotspot JVM GC最全的参数调整列表：

 

http://blogs.sun.com/watt/resource/jvm-options-list.html

http://www.cnblogs.com/totti19841106/archive/2009/01/12/1374274.html

 

有关JVM默认值的参考资料如下：

https://gist.github.com/827140

http://hg.openjdk.java.net/jdk6/jdk6/hotspot/file/tip/src/share/vm/runtime/globals.hpp

 

Java 5以上版本（包含Java 5）GC的调整参数包含以下内容：

 

1.虚拟机GC性能调整工具参数：

 

–XX:+PrintGCDetails：

–XX:+PrintGCTimeStamps：

-XX:-DisableExplicitGC

-XX:+UseGCOverheadLimit

-XX:+StringCache

-XX:LargePageSizeInBytes=4m

-Xnoclassgc

-XX:MaxTenuringThreshold=<n>

指定一个 object 在经历了 n 次 young gc 后转移到 old generation 区 , 在 linux64 的 java6 下默认值是 15, 此参数对于 throughput collector 无效 , 如 :-XX:MaxTenuringThreshold=31

-XX:+UseFastAccessorMethods

get,set 方法转成本地代码

-XX:+PrintGCApplicationStoppedTime

打应垃圾收集时 , 系统的停顿时间 , 如 :

Total time for which application threads were stopped: 0.0225920 seconds

-Xmn<n>                       

指定 jvm 中 New Generation 的大小 , 如 :-Xmn256m。 这个参数很影响性能， 如果你的程序需要比较多的临时内存， 建议设置到512M， 如果用的少， 尽量降低这个数值， 一般来说128／256足以使用了。

-Xss<n>                       

指定线程桟大小 , 如 :-Xss128k， 一般来说，webx框架下的应用需要256K。 如果你的程序有大规模的递归行为， 请考虑设置到512K／1M。 这个需要全面的测试才能知道。 不过， 256K已经很大了。 这个参数对性能的影响比较大的。

 

-XX:PretenureSizeThreshold =<value>:当对象大于该值就直接分配到堆的 ‘老生代’ 区域

2.GC的关键选项参数：

 

2.1堆和代的大小调整参数

 

Option	Default	Description
-Xms<n>		Initial size, in bytes, of the heap.
–Xmx<n>		Maximum size, in bytes, of the heap.
–XX:MinHeapFreeRatio=minimum and –XX:MaxHeapFreeRatio=maximum	40 (min) 70 (max)	Target range for the proportion of free space to total heap size. These are applied per generation. For example, if minimum is 30 and the percent of free space in a generation falls below 30%, the size of the generation is expanded so as to have 30% of the space free. Similarly, if maximum is 60 and the percent of free space exceeds 60%, the size of the generation is shrunk so as to have only 60% of the space free.
–XX:NewSize=n		Default initial size of the new (young) generation in bytes.
–XX:NewRatio=n	2 on client JVM, 8 on server JVM	Ratio between the young and old generations. For example, if n is 3, then the ratio is 1:3 and the combined size of Eden and the survivor spaces is one fourth of the total size of the young and old generations.
–XX:SurvivorRatio=n	32	Ratio between each survivor space and Eden. For example, if n is 7, each survivor space is one–ninth of the young generation (not one–eighth, because there are two survivor spaces).
–XX:MaxPermSize=n	Platform–dependent	Maximum size of the permanent generation.

 

2.3垃圾回收器选择参数

 

 

 

Option	Garbage Collector Selected
–XX:+UseSerialGC	串行回收器
–XX:+UseParallelGC	并行回收器
–XX:+UseParallelOldGC	Parallel compacting
–XX:+UseConcMarkSweepGC	Concurrent mark–sweep (CMS)

2.4并行（Java5 以及以上版本-Server 模式默认的垃圾回收器）和并行压缩垃圾回收器的GC调整参数

Option	Default	Description
–XX:ParallelGCThreads=n	The number of CPUs	Number of garbage collector threads.
–XX:MaxGCPauseMillis=n	No default	Indicates to the collector that pause times of n milliseconds or less are desired.
–XX:GCTimeRatio=n	99	Number that sets a goal that 1/(1+n) of the total time be spent on garbage collection.

 

-XX:YoungGenerationSizeIncrement= <Y>

-XX:TenuredGenerationSizeIncrement=<T>

-XX:AdaptiveSizeDecrementScaleFactor=<D>

2.5 CMS垃圾回收器的GC调整参数

 

Option	Default	Description
–XX:+CMSIncrementalMode	Disabled	Enables a mode in which the concurrent phases are done incrementally, periodically stopping the concurrent phase to yield back the processor to the application.
–XX:+CMSIncrementalPacing	Disabled	Enables automatic control of the amount of work the CMS collector is allowed to do before giving up the processor, based on application behavior.
–XX:ParallelGCThreads=n	The number of CPUs	Number of garbage collector threads for the parallel young generation collections and for the parallel parts of the old generation collections.

 

补充参数：

-XX:CMSInitiatingOccupancyFraction

-XX:+CMSPermGenSweepingEnabled
-XX:+CMSClassUnloadingEnabled

-XX:+UseCMSInitiatingOccupancyOnly

指示只有在 old generation 在使用了初始化的比例后 concurrent collector 启动收集

 

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

http://www.md.pp.ru/~eu/jdk6options.html