ManagementFactory (二) getMemoryMXBean
MemoryMXBean
- package cn.zno.outofmomery;
- import java.lang.management.ManagementFactory;
- import java.lang.management.MemoryMXBean;
- import java.util.ArrayList;
- import java.util.List;
- public class Test {
- MemoryMXBean memoryMXBean;
- {
- memoryMXBean = ManagementFactory.getMemoryMXBean();
- System.out.println(memoryMXBean.isVerbose());
- }
- void h(){
- List<byte[]> list = new ArrayList<byte[]>();
- while(true){
- // System.out.println(memoryMXBean.getNonHeapMemoryUsage());
- System.out.println(memoryMXBean.getHeapMemoryUsage());
- list.add(new byte[1024*1024]);
- }
- }
- public static void main(String[] args) {
- new Test().h();
- }
- }
- 垃圾回收是否启用
- 获取堆内存使用情况
- 获取非堆内存使用情况
VM args
- -verbose:gc -XX:+PrintGCDetails
或
- -verbose:gc
或
- -Xloggc:D://data.log
或
- -Xloggc:D://data.log -XX:+PrintGCDetails
运行结果:
- true
- init = (32768K) used = (594K) committed = (31680K) max = (31680K)
- init = (32768K) used = (1618K) committed = (31680K) max = (31680K)
- init = (32768K) used = (2642K) committed = (31680K) max = (31680K)
- init = (32768K) used = (3666K) committed = (31680K) max = (31680K)
- init = (32768K) used = (4690K) committed = (31680K) max = (31680K)
- init = (32768K) used = (5714K) committed = (31680K) max = (31680K)
- init = (32768K) used = (6738K) committed = (31680K) max = (31680K)
- init = (32768K) used = (7762K) committed = (31680K) max = (31680K)
- [GC 7762K->7548K(31680K), 0.0032242 secs]
- init = (32768K) used = (8572K) committed = (31680K) max = (31680K)
- init = (32768K) used = (9689K) committed = (31680K) max = (31680K)
- init = (32768K) used = (10887K) committed = (31680K) max = (31680K)
- init = (32768K) used = (11911K) committed = (31680K) max = (31680K)
- init = (32768K) used = (12935K) committed = (31680K) max = (31680K)
- init = (32768K) used = (13959K) committed = (31680K) max = (31680K)
- init = (32768K) used = (14983K) committed = (31680K) max = (31680K)
- init = (32768K) used = (16007K) committed = (31680K) max = (31680K)
- [GC 16007K->15739K(31680K), 0.0032697 secs]
- init = (32768K) used = (16824K) committed = (31680K) max = (31680K)
- init = (32768K) used = (17849K) committed = (31680K) max = (31680K)
- init = (32768K) used = (18873K) committed = (31680K) max = (31680K)
- init = (32768K) used = (19897K) committed = (31680K) max = (31680K)
- init = (32768K) used = (20921K) committed = (31680K) max = (31680K)
- init = (32768K) used = (21945K) committed = (31680K) max = (31680K)
- init = (32768K) used = (22969K) committed = (31680K) max = (31680K)
- init = (32768K) used = (23993K) committed = (31680K) max = (31680K)
- [Full GC 23993K->23932K(31680K), 0.0051448 secs]
- init = (32768K) used = (24956K) committed = (31680K) max = (31680K)
- init = (32768K) used = (26020K) committed = (31680K) max = (31680K)
- init = (32768K) used = (27044K) committed = (31680K) max = (31680K)
- init = (32768K) used = (28068K) committed = (31680K) max = (31680K)
- init = (32768K) used = (29092K) committed = (31680K) max = (31680K)
- init = (32768K) used = (30116K) committed = (31680K) max = (31680K)
- init = (32768K) used = (31140K) committed = (31680K) max = (31680K)
- [Full GC 31140K->31100K(31680K), 0.0034119 secs]
- [Full GC 31100K->31090K(31680K), 0.0033546 secs]
- Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
- at cn.zno.outofmomery.Test.h(Test.java:)
- at cn.zno.outofmomery.Test.main(Test.java:)
垃圾回收格式解读
init = 33554432(32768K) used = 24568936(23993K) committed = 32440320(31680K) max = 32440320(31680K)
[Full GC 23993K->23932K(31680K), 0.0051448 secs]
-----------------------------------------------------------
[Full GC gc前used->gc后used(committed), 耗费时间]
参考 : https://www.oracle.com/technetwork/java/javase/gc-tuning-6-140523.html
Measurement
Throughput and footprint are best measured using metrics particular to the application. For example, throughput of a web server may be tested using a client load generator, while footprint of the server might be measured on the Solaris Operating System using the pmap
command. On the other hand, pauses due to garbage collection are easily estimated by inspecting the diagnostic output of the virtual machine itself.
The command line option -verbose:gc
causes information about the heap and garbage collection to be printed at each collection. For example, here is output from a large server application:
[GC 325407K->83000K(776768K), 0.2300771 secs]
[GC 325816K->83372K(776768K), 0.2454258 secs]
[Full GC 267628K->83769K(776768K), 1.8479984 secs]
Here we see two minor collections followed by one major collection. The numbers before and after the arrow (e.g., 325407K->83000K
from the first line) indicate the combined size of live objects before and after garbage collection, respectively. After minor collections the size includes some objects that are garbage (no longer alive) but that cannot be reclaimed. These objects are either contained in the tenured generation, or referenced from the tenured or permanent generations.
The next number in parentheses (e.g., (776768K)
again from the first line) is the committed size of the heap: the amount of space usable for java objects without requesting more memory from the operating system. Note that this number does not include one of the survivor spaces, since only one can be used at any given time, and also does not include the permanent generation, which holds metadata used by the virtual machine.
The last item on the line (e.g., 0.2300771 secs
) indicates the time taken to perform the collection; in this case approximately a quarter of a second.
The format for the major collection in the third line is similar.
The format of the output produced by -verbose:gc is subject to change in future releases. |
The option -XX:+PrintGCDetails
causes additional information about the collections to be printed. An example of the output with -XX:+PrintGCDetails
using the serial garbage collector is shown here.
[GC [DefNew: 64575K->959K(64576K), 0.0457646 secs] 196016K->133633K(261184K), 0.0459067 secs]
indicates that the minor collection recovered about 98% of the young generation, DefNew: 64575K->959K(64576K)
and took 0.0457646 secs
(about 45 milliseconds).
The usage of the entire heap was reduced to about 51% 196016K->133633K(261184K)
and that there was some slight additional overhead for the collection (over and above the collection of the young generation) as indicated by the final time of 0.0459067 secs
.
The option -XX:+PrintGCTimeStamps
will add a time stamp at the start of each collection. This is useful to see how frequently garbage collections occur.
111.042: [GC 111.042: [DefNew: 8128K->8128K(8128K), 0.0000505 secs]111.042: [Tenured: 18154K->2311K(24576K), 0.1290354 secs] 26282K->2311K(32704K), 0.1293306 secs]
The collection starts about 111 seconds into the execution of the application. The minor collection starts at about the same time. Additionally the information is shown for a major collection delineated by Tenured. The tenured generation usage was reduced to about 10% 18154K->2311K(24576K)
and took 0.1290354 secs
(approximately 130 milliseconds).
As was the case with -verbose:gc , the format of the output produced by -XX:+PrintGCDetails is subject to change in future releases. |
ManagementFactory (二) getMemoryMXBean的更多相关文章
- java 利用ManagementFactory获取jvm,os的一些信息--转
原文地址:http://blog.csdn.net/dream_broken/article/details/49759043 想了解下某个Java项目的运行时jvm的情况,可以使用一些监控工具,比如 ...
- java监控之ManagementFactory分析
The ManagementFactory class is a factory class for getting managed beans for the Java platform. This ...
- JMX学习笔记(二)-Notification
Notification通知,也可理解为消息,有通知,必然有发送通知的广播,JMX这里采用了一种订阅的方式,类似于观察者模式,注册一个观察者到广播里,当有通知时,广播通过调用观察者,逐一通知. 这里写 ...
- 深入理解java虚拟机---JDK8-废弃永久代(PermGen)迎来元空间(Metaspace)(十二)
引用:https://www.cnblogs.com/yulei126/p/6777323.html JDK8-废弃永久代(PermGen)迎来元空间(Metaspace) 1.背景 2.为什么废 ...
- 【小程序分享篇 二 】web在线踢人小程序,维持用户只能在一个台电脑持登录状态
最近离职了, 突然记起来还一个小功能没做, 想想也挺简单,留下代码和思路给同事做个参考. 换工作心里挺忐忑, 对未来也充满了憧憬与担忧.(虽然已是老人, 换了N次工作了,但每次心里都和忐忑). 写写代 ...
- 前端开发中SEO的十二条总结
一. 合理使用title, description, keywords二. 合理使用h1 - h6, h1标签的权重很高, 注意使用频率三. 列表代码使用ul, 重要文字使用strong标签四. 图片 ...
- 【疯狂造轮子-iOS】JSON转Model系列之二
[疯狂造轮子-iOS]JSON转Model系列之二 本文转载请注明出处 —— polobymulberry-博客园 1. 前言 上一篇<[疯狂造轮子-iOS]JSON转Model系列之一> ...
- 【原】Android热更新开源项目Tinker源码解析系列之二:资源文件热更新
上一篇文章介绍了Dex文件的热更新流程,本文将会分析Tinker中对资源文件的热更新流程. 同Dex,资源文件的热更新同样包括三个部分:资源补丁生成,资源补丁合成及资源补丁加载. 本系列将从以下三个方 ...
- 谈谈一些有趣的CSS题目(十二)-- 你该知道的字体 font-family
开本系列,谈谈一些有趣的 CSS 题目,题目类型天马行空,想到什么说什么,不仅为了拓宽一下解决问题的思路,更涉及一些容易忽视的 CSS 细节. 解题不考虑兼容性,题目天马行空,想到什么说什么,如果解题 ...
随机推荐
- 【转】Java之 内存区域和GC机制
转自:Leo Chin 目录 Java垃圾回收概况 Java内存区域 Java对象的访问方式 Java内存分配机制 Java GC机制 垃圾收集器 Java垃圾回收概况 Java GC(Garbage ...
- Python中字符串的使用
这篇文章主要介绍python当中用的非常多的一种内置类型——str.它属于python中的Sequnce Type(序列类型).python中一共7种序列类型,分别为str(字符串),unicode( ...
- 【英语】Bingo口语笔记(4) - Pick系列
take your pick. 你挑吧 pick on 找茬
- pipe()管道最基本的IPC机制
<h4>进程间通信 fork pipe pie_t 等用法(管道机制 通信)</h4>每个进程各自有不同的用户地址空间,任何一个进程的全局变量在另一个进程中都看不到,所以进程之 ...
- grep -A -B选项详解和mysqlbinlog
grep的-A-B-选项详解(转)[@more@] grep能找出带有关键字的行,但是工作中有时需要找出该行前后的行,下面是解释 1. grep -A1 keyword filename 找出file ...
- 计算机网络——TCP三次、四次握手详解
三次握手:建立TCP连接 连接建立过程: B的TCP服务器进程先创建传输控制块TCB(存储了每一个连接中的一些重要信息,如:TCP连接表,到发送和接收缓存的指针,到重传队列的指针,当前的发送和接收序号 ...
- 基于CentOS与VmwareStation10搭建Oracle11G RAC 64集群环境:4.安装Oracle RAC FAQ-4.4.无法图形化安装Grid Infrastructure
无法图形化安装: [grid@linuxrac1 grid]$ ./runInstaller Starting Oracle Universal Installer... Checking Temp ...
- jquery ajax jsonp跨域调用实例代码
今天研究了AJAX使用JSONP进行跨域调用的方法,发现使用GET方式和POST方式都可以进行跨域调用,这里简单分享下,方便需要的朋友 客户端代码 复制代码 代码如下: <%@ Page Lan ...
- Java魔法类:sun.misc.Unsafe
Unsafe类在jdk 源码的多个类中用到,这个类的提供了一些绕开JVM的更底层功能,基于它的实现可以提高效率.但是,它是一把双刃剑:正如它的名字所预示的那样,它是Unsafe的,它所分配的内存需要手 ...
- centreon load average 的含义
下面图是centreon监控到的 load 信息 其中的 load1,load5,load15 分别说明上一分钟.最后五分钟以及最后十五分钟的系统负载均值.它们的数字当然是越小越好.数字越高,说明服务 ...