JVM Param

2019-01-10

JVM

jvm param

摘要: jvm param

JVM 参数

JVM 参数类型

标准参数

-help
-server -client
-version -showvesion
-cp -classpath

X参数

非标准化参数

-Xint 解释执行

$ java -Xint -version
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, interpreted mode)

-Xcomp 第一次使用就编译成本地代码

$ java -Xcomp -version
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, compiled mode)

-Xmixed 混合模式，JVM自己来决定是否编译成本地代码

$ java -version
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)

XX参数

非标准化参数，相对不稳定，主要用于JVM调优和调试

Boolean 类型

格式：-XX:[+-] 表示启用或者禁用name属性

exp ：-XX:+UseConcMarkSweepGC -XX:+UseG1GC
非 Boolean 类型

格式：-XX:= 表示name属性的值是value

exp ：-XX:MaxGCPauseMillis=500 -XX:GCTimeRatio=19

-Xmx -Xms …参数

不是X参数，而是XX参数

-Xms 等价于 -XX:InitialHeapSize= Heap初始化的大小

1 2	$ jinfo.exe -flag InitialHeapSize 20016 -XX:InitialHeapSize=1073741824 # 1G

-Xmx 等价于 -XX:MaxHeapSize= Heap的最大值

1 2	$ jinfo.exe -flag MaxHeapSize 20016 -XX:MaxHeapSize=1073741824 # 1G

-Xss 等价于 -XX:ThreadStackSize= 线程栈的大小，默认1M

1 2	$ jinfo.exe -flag ThreadStackSize 20016 -XX:ThreadStackSize=1024 # 1M

-Xmn 等价于 -XX:MaxNewSize= -XX:NewSize= 新生代的大小

$ jinfo.exe -flag MaxNewSize 20016
-XX:MaxNewSize=536870912 # 512M

$ jinfo.exe -flag NewSize 20016
-XX:NewSize=536870912	# 512M

查看JVM运行时参数

-XX:+PrintFlagsInitial 查看初始值

-XX:+PrintFlagsFinal 查看最终值

$ java -XX:+PrintFlagsFinal -version
[Global flags]
	...
	bool UseConcMarkSweepGC                        = false
    bool UseParallelGC                            := true
    uintx MaxHeapSize                             := 4227858432                		uintx MaxMetaspaceSize                         = 4294901760
    ...

:= 代表被修改后的值

= 表示默认值

-XX:+UnlockExperimentalVMOptions 解锁实验参数
-XX:+UnlockDiagnosticVMOptions 解锁诊断参数
-XX:+PrintCommandLineFlags 打印命令行参数

jinfo

$ jinfo.exe -flags 20016
Attaching to process ID 20016, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.144-b01
Non-default VM flags: -XX:-BytecodeVerificationLocal -XX:-BytecodeVerificationRemote -XX:CICompilerCount=4 -XX:+CMSClassUnloadingEnabled -XX:CMSInitiatingOccupancyFraction=80 -XX:CMSMaxAbortablePrecleanTime=5000 ...

jps 类似ps命令

$ jps
20016 YssBaseAdminApplication
11704 YssBaseAuthApplication
20824 AuthDataSyncApplication
14140 ApiGatewayApplication
21564 Jps

jstat

查看类装载信息

$ jstat -class 20016 1000 3
Loaded  Bytes  Unloaded  Bytes     Time
 17738 37286.3        0     0.0      14.17
 17738 37286.3        0     0.0      14.17
 17738 37286.3        0     0.0      14.17

查看垃圾收集信息

$ jstat -gc 20016 1000 3
 S0C    S1C    S0U    S1U      EC       EU        OC         OU       MC     MU    CCSC   CCSU   YGC     YGCT    FGC    FGCT     GCT
43648.0 43648.0 35638.4  0.0   436992.0 92098.5   524288.0   274918.1  116992.0 111496.1 14080.0 12956.9     26    1.148   0      0.000    1.148
43648.0 43648.0 35638.4  0.0   436992.0 92281.4   524288.0   274918.1  116992.0 111496.1 14080.0 12956.9     26    1.148   0      0.000    1.148
43648.0 43648.0 35638.4  0.0   436992.0 92305.6   524288.0   274918.1  116992.0 111496.1 14080.0 12956.9     26    1.148   0      0.000    1.148

_C 总量 _U使用量

S0、S1 S区

E Eden 区

O Old 区

M Metaspace 区

CC 压缩类空间

YGC Young GC 次数

YGCT Young GC 时间

FGC Full GC 次数

FGCT Full GC 时间

GCT 总的GC 时间

查看JIT编译信息

$ jstat -compiler 20016
Compiled Failed Invalid   Time   FailedType FailedMethod
   21115     11       0     5.54          1 org/apache/http/client/utils/URLEncodedUtils parse
   
$ jstat -printcompilation 20016
Compiled  Size  Type Method
   21127      9    1 org/apache/coyote/AbstractProcessor _jr$ip$socketWrapper

Compiled 编译的任务(把一个方法编译为本地方法)

参数docs

jmap

$ jmap -dump:format=b,file=heap.hprof 20016
Dumping heap to D:\arthas\heap.hprof ...
Heap dump file created

$ jmap -heap 20016
Attaching to process ID 20016, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.144-b01

using parallel threads in the new generation.
using thread-local object allocation.
Concurrent Mark-Sweep GC

Heap Configuration:
   MinHeapFreeRatio         = 40
   MaxHeapFreeRatio         = 70
   MaxHeapSize              = 1073741824 (1024.0MB)
   NewSize                  = 536870912 (512.0MB)
   MaxNewSize               = 536870912 (512.0MB)
   OldSize                  = 536870912 (512.0MB)
   NewRatio                 = 2
   SurvivorRatio            = 10
   MetaspaceSize            = 268435456 (256.0MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 536870912 (512.0MB)
   G1HeapRegionSize         = 0 (0.0MB)

Heap Usage:
New Generation (Eden + 1 Survivor Space):
   capacity = 492175360 (469.375MB)
   used     = 314702936 (300.12410736083984MB)
   free     = 177472424 (169.25089263916016MB)
   63.94122127527879% used
Eden Space:
   capacity = 447479808 (426.75MB)
   used     = 279453176 (266.50731658935547MB)
   free     = 168026632 (160.24268341064453MB)
   62.450454971143635% used
From Space:
   capacity = 44695552 (42.625MB)
   used     = 35249760 (33.616790771484375MB)
   free     = 9445792 (9.008209228515625MB)
   78.8663713114003% used
To Space:
   capacity = 44695552 (42.625MB)
   used     = 0 (0.0MB)
   free     = 44695552 (42.625MB)
   0.0% used
concurrent mark-sweep generation:
   capacity = 536870912 (512.0MB)
   used     = 318668000 (303.9054870605469MB)
   free     = 218202912 (208.09451293945312MB)
   59.35654044151306% used

63573 interned Strings occupying 7445616 bytes.

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