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JVM基本调优参数

2021年06月15日
0
未分类
，

指定堆大小

<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
1
2
3
4
5
<span class="line"><span class="comment">//指定堆最大</span></span><br><span class="line">-XX:Xmx1024m</span><br><span class="line"></span><br><span class="line"><span class="comment">//指定堆初始大小</span></span><br><span class="line">-XX:Xms1024m</span><br>
<span class="line"><span class="comment">//指定堆最大</span></span><br><span class="line">-XX:Xmx1024m</span><br><span class="line"></span><br><span class="line"><span class="comment">//指定堆初始大小</span></span><br><span class="line">-XX:Xms1024m</span><br>
//指定堆最大
-XX:Xmx1024m

//指定堆初始大小
-XX:Xms1024m

Java方法栈

指定线程的栈最大空间

<span class="line">1</span><br><span class="line">2</span><br>
<span class="line">1</span><br><span class="line">2</span><br>
1
2
<span class="line"><span class="comment">//默认256K</span></span><br><span class="line">-XX:Xss128K</span><br>
<span class="line"><span class="comment">//默认256K</span></span><br><span class="line">-XX:Xss128K</span><br>
//默认256K
-XX:Xss128K

影响GC因素：

局部变量表槽位复用

在方法体中声明的变量都会在局部变量表中，如果超过其作用域，则会被之后声明的变量复用，如果是引用类型，则会失去引用，被GC。但如果只是超过作用域但是没有被其他变量复用，则不会失去引用。

栈内分配

逃逸分析

用于分析引用类型声明的变量的作用域是否会逃逸出方法体，如果作用域只在方法体内且不返回，则可以标量替换

标量替换

指类引用类型声明时，如果可以被

TLAB

TLAB（Thread Local Allocation Buffer）本地线程分配缓存，在类加载之后分配内存时，如果开启了这个选项，则可以在堆中属于线程的缓存区分配内存，不需要到共享的堆区进行内存申请，避免内存申请失败。开启了这个会使得栈内分配失效

<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
1
2
3
4
5
<span class="line"><span class="comment">//开启TLAB</span></span><br><span class="line">-XX:+UseTLAB</span><br><span class="line"></span><br><span class="line"><span class="comment">//关闭</span></span><br><span class="line">-XX:-UseTLAB</span><br>
<span class="line"><span class="comment">//开启TLAB</span></span><br><span class="line">-XX:+UseTLAB</span><br><span class="line"></span><br><span class="line"><span class="comment">//关闭</span></span><br><span class="line">-XX:-UseTLAB</span><br>
//开启TLAB
-XX:+UseTLAB

//关闭
-XX:-UseTLAB

永久代&元空间

永久代

<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br>
<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br>
1
2
3
4
<span class="line"><span class="comment">//指定永久代初始大小</span></span><br><span class="line">-XX:PermSize64m</span><br><span class="line"><span class="comment">//指定最大永久代大小</span></span><br><span class="line">-XX:MaxPermSize128m</span><br>
<span class="line"><span class="comment">//指定永久代初始大小</span></span><br><span class="line">-XX:PermSize64m</span><br><span class="line"><span class="comment">//指定最大永久代大小</span></span><br><span class="line">-XX:MaxPermSize128m</span><br>
//指定永久代初始大小
-XX:PermSize64m
//指定最大永久代大小
-XX:MaxPermSize128m

元空间

元空间使用的是直接内存

<span class="line">1</span><br><span class="line">2</span><br>
<span class="line">1</span><br><span class="line">2</span><br>
1
2
<span class="line"><span class="comment">//指定元空间最大大小，默认无限制直到用光系统内存</span></span><br><span class="line">-XX:MaxMetaspaceSize512m</span><br>
<span class="line"><span class="comment">//指定元空间最大大小，默认无限制直到用光系统内存</span></span><br><span class="line">-XX:MaxMetaspaceSize512m</span><br>
//指定元空间最大大小，默认无限制直到用光系统内存
-XX:MaxMetaspaceSize512m

打印GC日志

jdk9之前

<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br>
<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br>
1
2
3
4
5
6
7
8
<span class="line"><span class="comment">//打印简单GC日志</span></span><br><span class="line">-XX:+PrintGC</span><br><span class="line"></span><br><span class="line"><span class="comment">//打印GC日志详情</span></span><br><span class="line">-XX:+PrintGCDetails</span><br><span class="line"></span><br><span class="line"><span class="comment">//获取堆信息</span></span><br><span class="line">-XX:+PrintHeadAtGC</span><br>
<span class="line"><span class="comment">//打印简单GC日志</span></span><br><span class="line">-XX:+PrintGC</span><br><span class="line"></span><br><span class="line"><span class="comment">//打印GC日志详情</span></span><br><span class="line">-XX:+PrintGCDetails</span><br><span class="line"></span><br><span class="line"><span class="comment">//获取堆信息</span></span><br><span class="line">-XX:+PrintHeadAtGC</span><br>
//打印简单GC日志
-XX:+PrintGC

//打印GC日志详情
-XX:+PrintGCDetails

//获取堆信息
-XX:+PrintHeadAtGC

jdk9、jdk10

<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
1
2
3
4
5
<span class="line"><span class="comment">//打印简单日志</span></span><br><span class="line">-Xlog:gc</span><br><span class="line"></span><br><span class="line"><span class="comment">//打印日志详情</span></span><br><span class="line">-Xlog:gc*</span><br>
<span class="line"><span class="comment">//打印简单日志</span></span><br><span class="line">-Xlog:gc</span><br><span class="line"></span><br><span class="line"><span class="comment">//打印日志详情</span></span><br><span class="line">-Xlog:gc*</span><br>
//打印简单日志
-Xlog:gc

//打印日志详情
-Xlog:gc*

GC日志查看

注意：因为GC日志输出时机的原因，显示的数据可能并不准确，有问题的地方需要重新校对

DefNew
DefNew ：新生代

eden
eden 、
from
from 、
to
to

Tenured
Tenured ：老年代

Perm
Perm ：永久代

类加载/卸载追踪

jdk9之前

<span class="line">1</span><br>
<span class="line">1</span><br>
1
<span class="line">-XX:+TraceClassLoading</span><br>
<span class="line">-XX:+TraceClassLoading</span><br>
-XX:+TraceClassLoading

jdk9、jdk10

<span class="line">1</span><br>
<span class="line">1</span><br>
1
<span class="line">-Xlog:<span class="class"><span class="keyword">class</span>+<span class="title">load</span></span>=info</span><br>
<span class="line">-Xlog:<span class="class"><span class="keyword">class</span>+<span class="title">load</span></span>=info</span><br>
-Xlog:class+load=info

柱状图分析

<span class="line">1</span><br><span class="line">2</span><br>
<span class="line">1</span><br><span class="line">2</span><br>
1
2
<span class="line"><span class="comment">//配合在控制台使用ctrl+Break展示信息</span></span><br><span class="line">-XX:+PrintClassHistogram</span><br>
<span class="line"><span class="comment">//配合在控制台使用ctrl+Break展示信息</span></span><br><span class="line">-XX:+PrintClassHistogram</span><br>
//配合在控制台使用ctrl+Break展示信息
-XX:+PrintClassHistogram

查看系统参数

<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
1
2
3
4
5
<span class="line"><span class="comment">//程序运行时展示手动配置的参数</span></span><br><span class="line">-XX:+PrintVMOptions</span><br><span class="line"></span><br><span class="line"><span class="comment">//自动配置&手动配置的参数都展示</span></span><br><span class="line">-XX:+PrintCommandLineFlags</span><br>
<span class="line"><span class="comment">//程序运行时展示手动配置的参数</span></span><br><span class="line">-XX:+PrintVMOptions</span><br><span class="line"></span><br><span class="line"><span class="comment">//自动配置&手动配置的参数都展示</span></span><br><span class="line">-XX:+PrintCommandLineFlags</span><br>
//程序运行时展示手动配置的参数
-XX:+PrintVMOptions

//自动配置&手动配置的参数都展示
-XX:+PrintCommandLineFlags

指定堆大小

<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
1
2
3
4
5
<span class="line"><span class="comment">//指定堆最大</span></span><br><span class="line">-XX:Xmx1024m</span><br><span class="line"></span><br><span class="line"><span class="comment">//指定堆初始大小</span></span><br><span class="line">-XX:Xms1024m</span><br>
<span class="line"><span class="comment">//指定堆最大</span></span><br><span class="line">-XX:Xmx1024m</span><br><span class="line"></span><br><span class="line"><span class="comment">//指定堆初始大小</span></span><br><span class="line">-XX:Xms1024m</span><br>
//指定堆最大
-XX:Xmx1024m

//指定堆初始大小
-XX:Xms1024m

Java方法栈

指定线程的栈最大空间

<span class="line">1</span><br><span class="line">2</span><br>
<span class="line">1</span><br><span class="line">2</span><br>
1
2
<span class="line"><span class="comment">//默认256K</span></span><br><span class="line">-XX:Xss128K</span><br>
<span class="line"><span class="comment">//默认256K</span></span><br><span class="line">-XX:Xss128K</span><br>
//默认256K
-XX:Xss128K

影响GC因素：

局部变量表槽位复用

在方法体中声明的变量都会在局部变量表中，如果超过其作用域，则会被之后声明的变量复用，如果是引用类型，则会失去引用，被GC。但如果只是超过作用域但是没有被其他变量复用，则不会失去引用。

栈内分配

逃逸分析

用于分析引用类型声明的变量的作用域是否会逃逸出方法体，如果作用域只在方法体内且不返回，则可以标量替换

标量替换

指类引用类型声明时，如果可以被

TLAB

TLAB（Thread Local Allocation Buffer）本地线程分配缓存，在类加载之后分配内存时，如果开启了这个选项，则可以在堆中属于线程的缓存区分配内存，不需要到共享的堆区进行内存申请，避免内存申请失败。开启了这个会使得栈内分配失效

<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
1
2
3
4
5
<span class="line"><span class="comment">//开启TLAB</span></span><br><span class="line">-XX:+UseTLAB</span><br><span class="line"></span><br><span class="line"><span class="comment">//关闭</span></span><br><span class="line">-XX:-UseTLAB</span><br>
<span class="line"><span class="comment">//开启TLAB</span></span><br><span class="line">-XX:+UseTLAB</span><br><span class="line"></span><br><span class="line"><span class="comment">//关闭</span></span><br><span class="line">-XX:-UseTLAB</span><br>
//开启TLAB
-XX:+UseTLAB

//关闭
-XX:-UseTLAB

永久代&元空间

永久代

<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br>
<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br>
1
2
3
4
<span class="line"><span class="comment">//指定永久代初始大小</span></span><br><span class="line">-XX:PermSize64m</span><br><span class="line"><span class="comment">//指定最大永久代大小</span></span><br><span class="line">-XX:MaxPermSize128m</span><br>
<span class="line"><span class="comment">//指定永久代初始大小</span></span><br><span class="line">-XX:PermSize64m</span><br><span class="line"><span class="comment">//指定最大永久代大小</span></span><br><span class="line">-XX:MaxPermSize128m</span><br>
//指定永久代初始大小
-XX:PermSize64m
//指定最大永久代大小
-XX:MaxPermSize128m

元空间

元空间使用的是直接内存

<span class="line">1</span><br><span class="line">2</span><br>
<span class="line">1</span><br><span class="line">2</span><br>
1
2
<span class="line"><span class="comment">//指定元空间最大大小，默认无限制直到用光系统内存</span></span><br><span class="line">-XX:MaxMetaspaceSize512m</span><br>
<span class="line"><span class="comment">//指定元空间最大大小，默认无限制直到用光系统内存</span></span><br><span class="line">-XX:MaxMetaspaceSize512m</span><br>
//指定元空间最大大小，默认无限制直到用光系统内存
-XX:MaxMetaspaceSize512m

打印GC日志

jdk9之前

<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br>
<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br>
1
2
3
4
5
6
7
8
<span class="line"><span class="comment">//打印简单GC日志</span></span><br><span class="line">-XX:+PrintGC</span><br><span class="line"></span><br><span class="line"><span class="comment">//打印GC日志详情</span></span><br><span class="line">-XX:+PrintGCDetails</span><br><span class="line"></span><br><span class="line"><span class="comment">//获取堆信息</span></span><br><span class="line">-XX:+PrintHeadAtGC</span><br>
<span class="line"><span class="comment">//打印简单GC日志</span></span><br><span class="line">-XX:+PrintGC</span><br><span class="line"></span><br><span class="line"><span class="comment">//打印GC日志详情</span></span><br><span class="line">-XX:+PrintGCDetails</span><br><span class="line"></span><br><span class="line"><span class="comment">//获取堆信息</span></span><br><span class="line">-XX:+PrintHeadAtGC</span><br>
//打印简单GC日志
-XX:+PrintGC

//打印GC日志详情
-XX:+PrintGCDetails

//获取堆信息
-XX:+PrintHeadAtGC

jdk9、jdk10

<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
1
2
3
4
5
<span class="line"><span class="comment">//打印简单日志</span></span><br><span class="line">-Xlog:gc</span><br><span class="line"></span><br><span class="line"><span class="comment">//打印日志详情</span></span><br><span class="line">-Xlog:gc*</span><br>
<span class="line"><span class="comment">//打印简单日志</span></span><br><span class="line">-Xlog:gc</span><br><span class="line"></span><br><span class="line"><span class="comment">//打印日志详情</span></span><br><span class="line">-Xlog:gc*</span><br>
//打印简单日志
-Xlog:gc

//打印日志详情
-Xlog:gc*

GC日志查看

注意：因为GC日志输出时机的原因，显示的数据可能并不准确，有问题的地方需要重新校对

DefNew
DefNew ：新生代

eden
eden 、
from
from 、
to
to

Tenured
Tenured ：老年代

Perm
Perm ：永久代

类加载/卸载追踪

jdk9之前

<span class="line">1</span><br>
<span class="line">1</span><br>
1
<span class="line">-XX:+TraceClassLoading</span><br>
<span class="line">-XX:+TraceClassLoading</span><br>
-XX:+TraceClassLoading

jdk9、jdk10

<span class="line">1</span><br>
<span class="line">1</span><br>
1
<span class="line">-Xlog:<span class="class"><span class="keyword">class</span>+<span class="title">load</span></span>=info</span><br>
<span class="line">-Xlog:<span class="class"><span class="keyword">class</span>+<span class="title">load</span></span>=info</span><br>
-Xlog:class+load=info

柱状图分析

<span class="line">1</span><br><span class="line">2</span><br>
<span class="line">1</span><br><span class="line">2</span><br>
1
2
<span class="line"><span class="comment">//配合在控制台使用ctrl+Break展示信息</span></span><br><span class="line">-XX:+PrintClassHistogram</span><br>
<span class="line"><span class="comment">//配合在控制台使用ctrl+Break展示信息</span></span><br><span class="line">-XX:+PrintClassHistogram</span><br>
//配合在控制台使用ctrl+Break展示信息
-XX:+PrintClassHistogram

查看系统参数

<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
<span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br>
1
2
3
4
5
<span class="line"><span class="comment">//程序运行时展示手动配置的参数</span></span><br><span class="line">-XX:+PrintVMOptions</span><br><span class="line"></span><br><span class="line"><span class="comment">//自动配置&手动配置的参数都展示</span></span><br><span class="line">-XX:+PrintCommandLineFlags</span><br>
<span class="line"><span class="comment">//程序运行时展示手动配置的参数</span></span><br><span class="line">-XX:+PrintVMOptions</span><br><span class="line"></span><br><span class="line"><span class="comment">//自动配置&手动配置的参数都展示</span></span><br><span class="line">-XX:+PrintCommandLineFlags</span><br>
//程序运行时展示手动配置的参数
-XX:+PrintVMOptions

//自动配置&手动配置的参数都展示
-XX:+PrintCommandLineFlags

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文章目录：

  1. 指定堆大小
  2. Java方法栈
  3. 永久代&元空间
  4. 打印GC日志
  5. GC日志查看
  6. 类加载/卸载追踪
  7. 柱状图分析
  8. 查看系统参数
  9. 指定堆大小
  10. Java方法栈
  11. 永久代&元空间
  12. 打印GC日志
  13. GC日志查看
  14. 类加载/卸载追踪
  15. 柱状图分析
  16. 查看系统参数

成就墙：

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