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javaxss默认大小（java xss参数）

今日新闻 2022年05月29日
本文导读目录：

JVM线程的栈在64位Linux操作系统上的默认大小是多少

不显式设置-Xss或-XX:ThreadStackSize时，在Linux x64上ThreadStackSize的默认值就是1024KB，给Java线程创建栈会用这个参数指定的大小。这是前一块代码的意思。

如果把-Xss或者-XX:ThreadStackSize设为0，就是使用“系统默认值”。而在Linux x64上HotSpot VM给Java栈定义的“系统默认”大小也是1MB。

所以这个条件下普通Java线程的默认栈大小怎样都是1MB。

java jvm内存可以设置多少

-Xmx Java Heap最大值,默认值为物理内存的1/4,最佳设值应该视物理内存大小及计算机内其他内存开销而定;

-Xms Java Heap初始值,Server端JVM最好将-Xms和-Xmx设为相同值,开发测试机JVM可以保留默认值;

-Xmn Java Heap Young区大小,不熟悉最好保留默认值; -Xss 每个线程的Stack大小,不熟悉最好保留默认值;

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2. 如何分配JVM内存设置:

(1)当在命令提示符下启动并使用JVM时(只对当前运行的类Test生效): java -Xmx128m -Xms64m -Xmn32m -Xss16m Test (2)当在集成开发环境下(如eclipse)启动并使用JVM时:

a. 在eclipse根目录下打开eclipse.ini,默认内容为(这里设置的是运行当前开发工具的JVM内存分配): -vmargs -Xms40m -Xmx256m

-vmargs表示以下为虚拟机设置参数,可修改其中的参数值,也可添加-Xmn,-Xss,另外,eclipse.ini内还可以设置非堆内存,如:-XX:PermSize=56m,-XX:MaxPermSize=128m.

此处设置的参数值可以通过以下配置在开发工具的状态栏显示: 在eclipse根目录下创建文件options,文件内容为:org.eclipse.ui/perf/showHeapStatus=true

修改eclipse根目录下的eclipse.ini文件,在开头处添加如下内容: -debug options -vm javaw.exe

重新启动eclipse,就可以看到下方状态条多了JVM信息.

b. 打开eclipse-窗口-首选项-Java-已安装的JRE(对在当前开发环境中运行的java程序皆生效)

编辑当前使用的JRE,在缺省VM参数中输入:-Xmx128m -Xms64m -Xmn32m -Xss16m

c. 打开eclipse-运行-运行-Java应用程序(只对所设置的java类生效) 选定需设置内存分配的类-自变量,在VM自变量中输入:-Xmx128m -Xms64m

选定需设置内存分配的类-自变量,在VM自变量中输入:-Xmx128m -Xms64m -Xmn32m -Xss16m

注:如果在同一开发环境中同时进行了b和c设置,则b设置生效,c设置无效,如:

开发环境的设置为:-Xmx256m,而类Test的设置为:-Xmx128m -Xms64m,则运行Test时生效的设置为: -Xmx256m -Xms64m

(3)当在服务器环境下(如Tomcat)启动并使用JVM时(对当前服务器环境下所以Java程序生效): a. 设置环境变量: 变量名:CATALINA_OPTS

变量值:-Xmx128m -Xms64m -Xmn32m -Xss16m

3

b. 打开Tomcat根目录下的bin文件夹,编辑catalina.bat,将其中

的%CATALINA_OPTS%(共有四处)替换为:-Xmx128m -Xms64m -Xmn32m -Xss16m

如何设置Java虚拟机JVM启动内存参数

-Xmx Java Heap最大值，默认值为物理内存的1/4，最佳设值应该视物理内存大小及计算机内其他内存开销而定；

-Xms Java Heap初始值，Server端JVM最好将-Xms和-Xmx设为相同值，开发测试机JVM可以保留默认值；

-Xmn Java Heap Young区大小，不熟悉最好保留默认值；

-Xss 每个线程的Stack大小，不熟悉最好保留默认值；

2. 如何设置JVM内存分配：

（1）当在命令提示符下启动并使用JVM时（只对当前运行的类Test生效）：

java -Xmx128m -Xms64m -Xmn32m -Xss16m Test

（2）当在集成开发环境下（如eclipse）启动并使用JVM时：

a. 在eclipse根目录下打开eclipse.ini，默认内容为（这里设置的是运行当前开发工具的JVM内存分配）

怎么查看Java（jvm）虚拟机的大小

由于java应用的允许依赖于JVM（虚拟机），相应的内存配置显然也需要JVM来提供的，准备地说是通过/bin/java.exe的启动命令参数来实现的。具体的配置项如下几种：-XmxJavaHeap最大值（默认值为物理内存的1/4）-XmsJavaHeap初始值-XmnJavaHeapYoung区大小-Xss每个线程的Stack大小拓展，以下是几种使用示例：1、命令下启动应用并配置内存：java-Xmx128m-Xms64mTest2、eclipse内存配置：-vmargs-Xms40m-Xmx512m的配置信息，请自行搜索“jvm内存”。

java xms 怎么设置大小

在一些规模稍大的应用中，Java虚拟机（JVM）的内存设置尤为重要，想在项目中取得好的效率，GC（垃圾回收）的设置是第一步。

PermGen space：全称是Permanent Generation space.就是说是永久保存的区域,用于存放Class和Meta信息,Class在被Load的时候被放入该区域Heap space：存放Instance。

GC(Garbage Collection)应该不会对PermGen space进行清理,所以如果你的APP会LOAD很多CLASS的话,就很可能出现PermGen space错误

Java Heap分为3个区

1.Young

2.Old

3.Permanent

Young保存刚实例化的对象。当该区被填满时，GC会将对象移到Old区。Permanent区则负责保存反射对象，本文不讨论该区。

JVM的Heap分配可以使用-X参数设定，

-Xms

初始Heap大小

-Xmx

java heap最大值

-Xmn

young generation的heap大小

JVM有2个GC线程

第一个线程负责回收Heap的Young区

第二个线程在Heap不足时，遍历Heap，将Young 区升级为Older区

Older区的大小等于-Xmx减去-Xmn，不能将-Xms的值设的过大，因为第二个线程被迫运行会降低JVM的性能。

为什么一些程序频繁发生GC？

有如下原因：

1.程序内调用了System.gc()或Runtime.gc()。

2.一些中间件软件调用自己的GC方法，此时需要设置参数禁止这些GC。

3.Java的Heap太小，一般默认的Heap值都很小。

4.频繁实例化对象，Release对象 此时尽量保存并重用对象，例如使用StringBuffer()和String()。

如果你发现每次GC后，Heap的剩余空间会是总空间的50%，这表示你的Heap处于健康状态,许多Server端的Java程序每次GC后最好能有65%的剩余空间

经验之谈：

1．Server端JVM最好将-Xms和-Xmx设为相同值。为了优化GC，最好让-Xmn值约等于-Xmx的1/3。

2．一个GUI程序最好是每10到20秒间运行一次GC，每次在半秒之内完成。

注意：

1．增加Heap的大小虽然会降低GC的频率，但也增加了每次GC的时间。并且GC运行时，所有的用户线程将暂停，也就是GC期间，Java应用程序不做任何工作。

2．Heap大小并不决定进程的内存使用量。进程的内存使用量要大于-Xmx定义的值，因为Java为其他任务分配内存，例如每个线程的Stack等。

Stack的设定

每个线程都有他自己的Stack。

-Xss

每个线程的Stack大小

Stack的大小限制着线程的数量。如果Stack过大就好导致内存溢漏。-Xss参数决定Stack大小，例如-Xss1024K。如果Stack太小，也会导致Stack溢漏。

硬件环境

硬件环境也影响GC的效率，例如机器的种类，内存，swap空间，和CPU的数量。

如果你的程序需要频繁创建很多transient对象，会导致JVM频繁GC。这种情况你可以增加机器的内存，来减少Swap空间的使用。

4种GC

1、第一种为单线程GC，也是默认的GC，该GC适用于单CPU机器。

2、第二种为Throughput GC，是多线程的GC，适用于多CPU，使用大量线程的程序。第二种GC与第一种GC相似，不同在于GC在收集Young区是多线程的，但在Old区和第一种一样，仍然采用单线程。-XX:+UseParallelGC参数启动该GC。

3、第三种为Concurrent Low Pause GC，类似于第一种，适用于多CPU，并要求缩短因GC造成程序停滞的时间。这种GC可以在Old区的回收同时，运行应用程序。-XX:+UseConcMarkSweepGC参数启动该GC。

4、第四种为Incremental Low Pause GC，适用于要求缩短因GC造成程序停滞的时间。这种GC可以在Young区回收的同时，回收一部分Old区对象。-Xincgc参数启动该GC。

单文件的JVM内存进行设置

默认的java虚拟机的大小比较小，在对大数据进行处理时java就会报错：java.lang.OutOfMemoryError。

设置jvm内存的方法，对于单独的.class，可以用下面的方法对Test运行时的jvm内存进行设置。

java -Xms64m -Xmx256m Test

-Xms是设置内存初始化的大小

-Xmx是设置最大能够使用内存的大小（最好不要超过物理内存大小）

tomcat启动jvm内存设置

Linux：

在/usr/local/apache-tomcat-5.5.23/bin目录下的catalina.sh添加：JAVA_OPTS='-Xms512m -Xmx1024m'要加“m”说明是MB，否则就是KB了，在启动tomcat时会报内存不足。

-Xms：初始值

-Xmx：最大值

-Xmn：最小值Windows

在catalina.bat最前面加入

set JAVA_OPTS=-Xms128m -Xmx350m 如果用startup.bat启动tomcat,OK设置生效.够成功的分配200M内存.但是如果不是执行startup.bat启动tomcat而是利用windows的系统服务启动tomcat服务,上面的设置就不生效了,就是说set JAVA_OPTS=-Xms128m -Xmx350m 没起作用.上面分配200M内存就OOM了..windows服务执行的是bin\tomcat.exe.他读取注册表中的值,而不是catalina.bat的设置.解决办法:

修改注册表HKEY_LOCAL_MACHINE\SOFTWARE\Apache Software Foundation\Tomcat Service Manager\Tomcat5\Parameters\JavaOptions

怎么把Java运行时的虚拟机参数的栈大小调到256K以上

-Xss256K: 设置每个线程的运行时栈的大小为 256K。

相关参数：

-Xmx，设置JVM最大内存；比如 -Xmx512M: 设置JVM最大内存为512M；

-Xms，设置JVM最小内存；比如 -Xms512M: 设置JVM最小内存为512M；

-Xmn，设置JVM年轻代内存；比如 -Xmn1G：设置年轻代内存为 1 G。

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我来说两句
黑客技术 3年前 (2022-05-30) | 回复
32m -Xss16m c. 打开eclipse-运行-运行-Java应用程序(只对所设置的java类生效) 选定需设置内存分配的类-自变量,在VM
黑客技术 3年前 (2022-05-29) | 回复
后，Heap的剩余空间会是总空间的50%，这表示你的Heap处于健康状态,许多Server端的Java程序每次GC后最好能有65%的剩余空间经验之谈：1．Server端JVM最好将-Xms和-Xmx设为相同值。为了优化GC，最好让-Xmn值约等于-Xmx的1/3。2．一个GUI程序最好是每10到20
黑客技术 3年前 (2022-05-29) | 回复
Xss 每个线程的Stack大小Stack的大小限制着线程的数量。如果Stack过大就好导致内存溢漏。-Xss参数决定Stack大小，例如-Xss1024K。如果
黑客技术 3年前 (2022-05-29) | 回复
（只对当前运行的类Test生效）：java -Xmx128m -Xms64m -Xmn32m -Xss16m Test（2）当在集成开发环境下（如eclipse）启动并使用J
黑客技术 3年前 (2022-05-29) | 回复
6m,而类Test的设置为:-Xmx128m -Xms64m,则运行Test时生效的设置为: -Xmx256m -Xms64m (3)当在服务器环
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