jvm调优案例

JVM调优

JVM 收集器

默认使用串行收集器， 单个cpu时适用吞吐收集器（throughput collector）：命令行参数：-XX:+UseParallelGC。在新生代使用并行清除收集策略，在旧生代和默认收集器相同。
适用：a、拥有2个以上cpu， b、临时对象较多的程序
-XX:ParallelGCThreads 并行收集线程数量，最好和cpu数量相当并发收集器（concurrent low pause collector）：命令行参数：-XX:+UseConcMarkSweepGC。在旧生代使用并发收集策略，大部分收集工作都是和应用并发进行的，在进行收集的时候，应用的暂停时间很短。默认配套打开 -XX:+UseParNewGC，会在新生代使用并行复制收集。
适用：a、拥有多个cpu， b、老对象较多的程序

-XX:+UseCMSCompactAtFullCollection：打开对年老代的压缩。可能会影响性能，但是可以消除碎片  
-XX:+UseFastAccessorMethods 原始类型的快速优化  
-XX:SurvivorRatio 新生区中，eden&survivor的比例，设置为8  
-XX:TargetSurvivorRatio 生存区需要做垃圾回收的比例值，默认为50%，设置高些可以更好的利用该区

设置jvm参数

$ java -jar -XX:MetaspaceSize=128m -XX:MaxMetaspaceSize=128m -Xms1024m -Xmx1024m -Xmn256m -Xss256k -XX:SurvivorRatio=8 -XX:+UseConcMarkSweepGC newframe-1.0.0.jar

$JAVA_ARGS  
.=  
"  
-Dresin.home=$SERVER_ROOT  
-server  
-Xmx3000M  
-Xms3000M  
-Xmn600M  
-XX:PermSize=500M  
-XX:MaxPermSize=500M  
-Xss256K  
-XX:+DisableExplicitGC  
-XX:SurvivorRatio=1  
-XX:+UseConcMarkSweepGC  
-XX:+UseParNewGC  
-XX:+CMSParallelRemarkEnabled  
-XX:+UseCMSCompactAtFullCollection  
-XX:CMSFullGCsBeforeCompaction=0  
-XX:+CMSClassUnloadingEnabled  
-XX:LargePageSizeInBytes=128M  
-XX:+UseFastAccessorMethods  
-XX:+UseCMSInitiatingOccupancyOnly  
-XX:CMSInitiatingOccupancyFraction=70  
-XX:SoftRefLRUPolicyMSPerMB=0  
-XX:+PrintClassHistogram  
-XX:+PrintGCDetails  
-XX:+PrintGCTimeStamps  
-XX:+PrintHeapAtGC  
-Xloggc:log/gc.log  
";

调优策略

JVM各个参数之间有一个平衡性的，另外根据业务类型和实际的运行环境都有不一样的效果。但是有些约定俗成的规定还是值得借鉴的：
1）堆内存不超过物理内存的3/4
2）年轻代的大小不超过堆内存的3/8
3）CMSInitiatingOccupancyFraction一般不低于70%

(Xmx-Xmn)*(1-CMSInitiatingOccupancyFraction/100)>=(Xmn-Xmn/(SurvivorRatior+2))

参考参数:

xms

xmn

survivor

xmn

gc

6G

6G

4

2G

CMSInitiatingOccupancyFraction=70

6G

6G

3

1.75G

CMSInitiatingOccupancyFraction=70

工具使用

查看线程cpu占用1

[root@localhost ~]# ps p 6515 -L -o pcpu,pid,tid,time,tname,cmd --sort pcpu  
%CPU   PID   TID     TIME TTY      CMD  
 0.0  6515  6515 00:00:00 pts/1    java -jar xxl-job-admin-2.0.2-SNAPSHOT.jar  
 0.0  6515  6523 00:00:04 pts/1    java -jar xxl-job-admin-2.0.2-SNAPSHOT.jar  
 0.0  6515  6529 00:00:00 pts/1    java -jar xxl-job-admin-2.0.2-SNAPSHOT.jar

查看线程cpu占用2

[root@localhost ~]# ps -mp 6515 -o THREAD,tid,time  
USER     %CPU PRI SCNT WCHAN  USER SYSTEM   TID     TIME  
root      0.3   -    - -         -      -     - 00:00:58  
root      0.0  19    - futex_    -      -  6515 00:00:00  
root      0.0  19    - futex_    -      -  6523 00:00:04  
root      0.0  19    - futex_    -      -  6529 00:00:00  
root      0.0  19    - futex_    -      -  6530 00:00:00

找到的线程ID转换为16进制格式

[root@localhost ~]# printf "%x
" 6523  
197b

打印线程的堆栈信息

[root@localhost ~]# jstack 6515 | grep 197b -A 30  
"DestroyJavaVM" #94 prio=5 os_prio=0 tid=0x00007f83f004b000 nid=0x197b waiting on condition [0x0000000000000000]  
   java.lang.Thread.State: RUNNABLE

"http-nio-9988-AsyncTimeout" #92 daemon prio=5 os_prio=0 tid=0x00007f83f0758000 nid=0x19e4 waiting on condition [0x00007f8352bee000]  
   java.lang.Thread.State: TIMED_WAITING (sleeping)  
    at java.lang.Thread.sleep(Native Method)  
    at org.apache.coyote.AbstractProtocol$AsyncTimeout.run(AbstractProtocol.java:1149)  
    at java.lang.Thread.run(Thread.java:748)

"http-nio-9988-Acceptor-0" #91 daemon prio=5 os_prio=0 tid=0x00007f83f0382800 nid=0x19e3 runnable [0x00007f8352cef000]  
   java.lang.Thread.State: RUNNABLE  
    at sun.nio.ch.ServerSocketChannelImpl.accept0(Native Method)  
    at sun.nio.ch.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:422)  
    at sun.nio.ch.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:250)  
    - locked <0x00000006c7c2ada0> (a java.lang.Object)  
    at org.apache.tomcat.util.net.NioEndpoint$Acceptor.run(NioEndpoint.java:482)  
    at java.lang.Thread.run(Thread.java:748)

"http-nio-9988-ClientPoller-1" #90 daemon prio=5 os_prio=0 tid=0x00007f83f11d1000 nid=0x19e2 runnable [0x00007f8352df0000]  
   java.lang.Thread.State: RUNNABLE  
    at sun.nio.ch.EPollArrayWrapper.epollWait(Native Method)  
    at sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:269)  
    at sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:93)  
    at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)  
    - locked <0x00000006c7c2b548> (a sun.nio.ch.Util$3)  
    - locked <0x00000006c7c2b538> (a java.util.Collections$UnmodifiableSet)  
    - locked <0x00000006c7c2b400> (a sun.nio.ch.EPollSelectorImpl)  
    at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)  
    at org.apache.tomcat.util.net.NioEndpoint$Poller.run(NioEndpoint.java:825)  
    at java.lang.Thread.run(Thread.java:748)

执行jmap把当前的堆dump下来

jmap -dump:live,format=b,file=dump.hprof 6515

将dump.hprof文件使用VisualVM来打开

SpringBoot TOMCAT调优

tomcat参数说明

maxThreads 客户请求最大线程数   
minSpareThreads Tomcat初始化时创建的 socket 线程数   
maxSpareThreads Tomcat连接器的最大空闲 socket 线程数   
enableLookups 若设为true, 则支持域名解析，可把 ip 地址解析为主机名   
redirectPort 在需要基于安全通道的场合，把客户请求转发到基于SSL 的 redirectPort 端口   
acceptAccount 监听端口队列最大数，满了之后客户请求会被拒绝（不能小于maxSpareThreads ）   
connectionTimeout 连接超时   
minProcessors 服务器创建时的最小处理线程数   
maxProcessors 服务器同时最大处理线程数   
URIEncoding URL统一编码

tomcat在springboot上的配置ServerProperties.java --> application.properties

server.tomcat.accesslog.enabled =  
server.tomcat.accesslog.pattern =  
server.tomcat.accesslog.directory =  
server.tomcat.accesslog.prefix =  
server.tomcat.accesslog.suffix =  
server.tomcat.accesslog.rotate =  
server.tomcat.accesslog.renameOnRotate =  
server.tomcat.accesslog.requestAttributesEnabled=  
server.tomcat.accesslog.buffered =  
server.tomcat.internalProxies =  
server.tomcat.protocolHeader =  
server.tomcat.protocolHeaderHttpsValue =  
server.tomcat.portHeader =  
server.tomcat.remoteIpHeader=  
server.tomcat.basedir =  
server.tomcat.backgroundProcessorDelay =  
server.tomcat.maxThreads =  
server.tomcat.minSpareThreads =  
server.tomcat.maxHttpPostSize =  
server.tomcat.maxHttpHeaderSize =  
server.tomcat.redirectContextRoot =  
server.tomcat.uriEncoding =  
server.tomcat.maxConnections =  
server.tomcat.acceptCount =  
server.tomcat.additionalTldSkipPatterns =

tomcat在application.yml上的配置

server:  
  tomcat:  
    min-spare-threads: 20  
    max-threads: 100  
  connection-timeout: 5000

参考:
1.JAVAEE文档:https://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html
2.深入理解JAVA虚拟机(内存模型+GC算法+JVM调优):https://www.cnblogs.com/yueshutong/p/9768298.html
3.JVM调优实践:https://blog.wangqi.love/articles/Java/JVM%E8%B0%83%E4%BC%98%E5%AE%9E%E8%B7%B5.html
4.JVM解读-性能调优实例:https://www.jianshu.com/p/2c4b091deaa3
5.扩容？先尝试一下JVM调优吧:https://sq.163yun.com/blog/article/211688346067283968
6.JVM调优参数简介、调优目标及调优经验https://blog.csdn.net/jisuanjiguoba/article/details/80176223
7.jvm优化必知系列——监控工具https://juejin.im/post/59e6c1f26fb9a0451c397a8c
8.JVM活学活用——优化springboothttps://cloud.tencent.com/developer/article/1089954
9.SpringBoot服务器压测对比(jetty、tomcat、undertow)https://my.oschina.net/shyloveliyi/blog/2980868