jvm参数详解

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* 布尔类型的参数
格式	-XX:+<option>   打开/-XX:-<option>   关闭
例如:	-XX:PrintGCDetails  打开GC信息(调优和定位内存回收问题经常使用)
* 数字型参数
格式	-XX:<option>=<number>
例如	-XX:NewRatio=2
* 字符型参数
格式	-XX:<option>=<string>
例如	-XX:HeapDumpPath=./java_pid.hprof

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$ java -help
Usage: java [-options] class [args...]
(to execute a class)
or  java [-options] -jar jarfile [args...]
(to execute a jar file)
where options include:
-d32	  use a 32-bit data model if available
-d64	  use a 64-bit data model if available
-server	  to select the "server" VM
The default VM is server,
because you are running on a server-class machine.

-cp <class search path of directories and zip/jar files>
-classpath <class search path of directories and zip/jar files>
A : separated list of directories, JAR archives,
and ZIP archives to search for class files.
-D<name>=<value>
set a system property
-verbose:[class|gc|jni]
enable verbose output
-version      print product version and exit
-version:<value>
require the specified version to run
-showversion  print product version and continue
-jre-restrict-search | -no-jre-restrict-search
include/exclude user private JREs in the version search
-? -help      print this help message
-X            print help on non-standard options
-ea[:<packagename>...|:<classname>]
-enableassertions[:<packagename>...|:<classname>]
enable assertions with specified granularity
-da[:<packagename>...|:<classname>]
-disableassertions[:<packagename>...|:<classname>]
disable assertions with specified granularity
-esa | -enablesystemassertions
enable system assertions
-dsa | -disablesystemassertions
disable system assertions
-agentlib:<libname>[=<options>]
load native agent library <libname>, e.g. -agentlib:hprof
see also, -agentlib:jdwp=help and -agentlib:hprof=help
-agentpath:<pathname>[=<options>]
load native agent library by full pathname
-javaagent:<jarpath>[=<options>]
load Java programming language agent, see java.lang.instrument
-splash:<imagepath>
show splash screen with specified image
See http://www.oracle.com/technetwork/java/javase/documentation/index.html for more details.
$ java -X
-Xmixed           mixed mode execution (default)
-Xint             interpreted mode execution only
-Xbootclasspath:<directories and zip/jar files separated by :>
set search path for bootstrap classes and resources
-Xbootclasspath/a:<directories and zip/jar files separated by :>
append to end of bootstrap class path
-Xbootclasspath/p:<directories and zip/jar files separated by :>
prepend in front of bootstrap class path
-Xdiag            show additional diagnostic messages
-Xnoclassgc       disable class garbage collection
-Xincgc           enable incremental garbage collection
-Xloggc:<file>    log GC status to a file with time stamps
-Xbatch           disable background compilation
-Xms<size>        set initial Java heap size
-Xmx<size>        set maximum Java heap size
-Xss<size>        set java thread stack size
-Xprof            output cpu profiling data
-Xfuture          enable<
10dce
/span> strictest checks, anticipating future default
-Xrs              reduce use of OS signals by Java/VM (see documentation)
-Xcheck:jni       perform additional checks for JNI functions
-Xshare:off       do not attempt to use shared class data
-Xshare:auto      use shared class data if possible (default)
-Xshare:on        require using shared class data, otherwise fail.
-XshowSettings    show all settings and continue
-XshowSettings:all
show all settings and continue
-XshowSettings:vm show all vm related settings and continue
-XshowSettings:properties
show all property settings and continue
-XshowSettings:locale
show all locale related settings and continue

The -X options are non-standard and subject to change without notice.

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package JDK.JVM;

import com.opslab.StringUtil;

import java.lang.management.ManagementFactory;
import java.util.List;

public class JvmParamerters {
public static void main(String[] args){
List<String> paramters = ManagementFactory.getRuntimeMXBean().getInputArguments();
System.out.println(StringUtil.join(paramters,":"));
}
}

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$ java -XX:+PrintGCDetails -Xloggc:./gc.log JDK.JVM.JvmParamerters
app starting...

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$ java -XX:+PrintGCDetails -Xloggc:./gc.log -XX:+PrintCommandLineFlags -XX:+PrintFlagsFinal \
JDK.JVM.JvmParamerters
-XX:InitialHeapSize=130056064 -XX:MaxHeapSize=2080897024 -XX:+PrintCommandLineFlags
-XX:+PrintFlagsFinal -XX:+PrintGC -XX:+PrintGCDetails -XX:+PrintGCTimeStamps
-XX:+UseCompressedOops -XX:+UseParallelGC
[Global flags]
...-javaagent:jarpath[=options]
uintx InitialHeapSize                          := 130056064       {product}
uintx InitialRAMFraction                        = 64              {product}
uintx InitialSurvivorRatio                      = 8               {product}
intx InitialTenuringThreshold                  = 7               {product}
uintx InitiatingHeapOccupancyPercent            = 45              {product}
bool Inline                                    = true            {product}
...
bool PrintGCDetails                           := true            {manageable}
bool PrintGCTaskTimeStamps                     = false           {product}
bool PrintGCTimeStamps                        := true            {manageable}
...

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-agentlib:jprofilerti=port=8849 -Xbootclasspath/a:/usr/local/jprofiler5/bin/agent.jar

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$ java -Xmx128 -Xms64 -Xmn32m -Xss16m Main