JVM study notes (seven) JVM parameters

8.1 JVM parameters

8.1.1 standard parameters

-version
-help
-server
-cp

8.1.2 -X parameters

Non-standard parameters may vary with the JDK version

-Xint   解释执行
-Xcomp  第一次使用就编译成本地代码
-Xmixed 混合模式，JVM自己解决

 

8.1.3 -XX parameters used frequently

Non-standardized parameters, relatively unstable, mainly for JVM tuning amount Debug

a.Boolean类型 
格式： -XX:[+-]<name> +或-表示启用或者禁用name属性 
比如： -XX:+UseConcMarkSweepGC 表示启用CMS类型的垃圾回收器 
      -XX:+UseG1GC 表示启用G1类型的垃圾回收器 
b.非Boolean类型 
格式：-XX<name>=<value>表示name属性的值是value 
比如：-XX:MaxGCPauseMillis=500

8.1.4 Other parameters

-Xms1000等价于-XX:InitialHeapSize=1000 
-Xmx1000等价于-XX:MaxHeapSize=1000 
-Xss100等价于-XX:ThreadStackSize=100

8.1.5 View Parameters

java -XX:+PrintFlagsFinal -version > flflags.txt

"=" Represents a default value ": =" represents a value of a user is modified or JVM

 

8.1.6 set the parameters of the way

• IDEA by VMoption

• Run jar package, java -XX: + UseG1GC xxx.jar

• web container can be set in the script

• (Marked manageable parameters of flags can be modified) by dynamically adjusting the parameters jinfo a java process

8.1.7 Unit Conversion

1Byte(字节)=8bit(位) 
1KB=1024Byte(字节) 
1MB=1024KB 
1GB=1024MB 
1TB=1024GB

(1)设置堆内存大小和参数打印 
    -Xmx100M -Xms100M -XX:+PrintFlagsFinal 
(2)查询+PrintFlagsFinal的值 
    :=true 
(3)查询堆内存大小MaxHeapSize 
    := 104857600 
(4)换算104857600(Byte)/1024=102400(KB) 
    102400(KB)/1024=100(MB) 
(5)结论
  104857600是字节单位 

8.1.8 Common Parameter Meaning

parameter	meaning	Explanation
-XX:CICompilerCount=3	The maximum number of parallel compilation	If the set is greater than 1, to improve the compilation speed, stability decreases
-XX:InitialHeapSize=100M	Initialization heap size	Shorthand -Xms100M
-XX:MaxHeapSize=100M	The maximum heap size	Shorthand -Xmx100M
-XX:NewSize=20M	Set the size of the new generation
-XX:MaxNewSize=40M	The maximum size of the new generation
-XX:OldSize=50M	Set old's size
-XX:MetaspaceSize=50M	Area size setting method
-XX:MaxMetaspaceSize=50M	The maximum size of the method area
-XX:+UseParallelGC	Use ParallelGC	The new generation, the throughput priority
-XX:+UseParallelOldGC	Use ParallelOldGC	Years old, throughput priority
-XX:+UseConcMarkSweepGC	Use CMS	Years old, dwell time priority
-XX:+UseG1GC	Use G1	Old and new era, pause time priority
-XX:NewRatio	The ratio of old and new	Example: -XX: NewRatio = 4, then the new: Old = 1: 4, the new generation of memory occupied by heap 1/5
-XX:SurvivorRatio	Eden ratio of the two area S and	Example: -XX: SurvivorRatio = 8, that is, (S0 + S1): Eden = 2: 8,
-XX:+HeapDumpOnOutOffMemoryError	Start heap overflow Print	When the heap memory overflow occurs (OOM), the dump file generated automatically
-XX:HeapDumpPath=heap.hprof	Specified directory heap overflow printing	Represents a heap.hprof generate files in the current directory
-XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps –Xloggc:log/gc.log	Print GC logs	You can use different garbage collectors, view comparison of the GC
-Xss128k	Set the stack size for each thread	Experience is the best 3000-5000
-XX:MaxTenuringThreshold=6	Enhance the maximum threshold of old age	The default value is 15
-XX:InitiatingHeapOccupancyPercent	Heap memory usage accounting concurrent GC cycle start	Used G1 garbage collection like it to trigger concurrent GC cycle, based on the entire heap usage, 0 stands for "GC cycle has been implementing the" default value is 45
-XX:G1HeapWastePercent	Allow the waste heap space accounting	The default value is 10%, if concurrent mark recoverable space is less than 10% does not trigger MixedGC
-XX:MaxGCPauseMillis=200ms	G1 maximum pause time	Dwell time is not too small, too small will lead to G1 keep up with the speed of garbage generated, triggers Full GC.
-XX:ConcGCThreads=n	Use of concurrent garbage collector thread count	The default value is set according to the JVM runtime platform
-XX:G1MixedGCLiveThresholdPercent=65	Mixing garbage collection cycle set to include the area occupied by the old threshold	The default occupancy rate of 65%
-XX:G1MixedGCCountTarget=8	After the cycle is completed flag is set, the upper limit of the data on survival of old G1MixedGCLiveThresholdPercent execution target frequency region of mixed waste collected	Default eight mixed garbage collection, mixed garbage collection is aimed primarily controlled within this target letter
-XX:G1OldCSetRegionThresholdPercent=1	描述Mixed GC时，Old Region 被加入到CSet中	默认情况下，G1只把10%的Old Region加入到CSet中

 

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When I let go of what I am , I become what I might be.
走出舒适圈，遇见更好的自己。

目录 8.1 JVM参数 8.1.1 标准参数 8.1.2 -X参数 8.1.3 -XX参数 使用频繁 8.1.4 其他参数 8.1.5 查看参数 8.1.6 设置参数的方式 8.1.7 单位换算 8.1.8 常用参数含义

[Mùlù 8.1 JVM cānshù 8.1.1 Biāozhǔn cānshù 8.1.2 -X cānshù 8.1.3 -XX cānshù shǐyòng pínfán 8.1.4 Qítā cānshù 8.1.5 Chákàn cānshù 8.1.6 Shèzhì cān shǔ de fāngshì 8.1.7 Dānwèi huànsuàn 8.1.8 Chángyòng cānshù hányì]

 

table of Contents



8.1 JVM parameters

8.1.1 standard parameters

8.1.2 -X parameters

8.1.3 -XX parameters used frequently

8.1.4 Other parameters

8.1.5 View Parameters

8.1.6 set the parameters of the way

8.1.7 Unit Conversion

8.1.8 Common Parameter Meaning