JVM tuning and finishing

JVM 收集器

1. The serial collector is used by default, 单个cpu时适用

2. Throughput collector（throughput collector）：命令行参数：-XX:+UseParallelGC.Use a parallel cleanup collection strategy in the young generation,Same as default collector in old generation.
   适用：a、拥有2个以上cpu, b、Programs with many temporary objects
   -XX:ParallelGCThreads Number of parallel collection threads,最好和cpu数量相当

3. 并发收集器（concurrent low pause collector）：命令行参数：-XX:+UseConcMarkSweepGC.Use concurrent collection strategy in old generation,Most of the collection work happens concurrently with the application,when collecting,The app's pause time is short.Open by default -XX:+UseParNewGC,A parallel copy collection is used in the young generation.
   适用：a、拥有多个cpu, b、Programs with more old objects

-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 The proportion of the survival area that needs to be garbage collected,默认为50%,Set higher to make better use of this area

• 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

JVMThere is a balance between the various parameters,In addition, there are different effects according to the business type and the actual operating environment.But some conventions are still worth learning from：
1）Heap memory does not exceed physical memory3/4 
2）The size of the young generation does not exceed the heap memory3/8 
3）CMSInitiatingOccupancyFraction一般不低于70% 

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

• 参考参数:

工具使用

• 查看线程cpu占用1

[[email protected] ~]# 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

[[email protected] ~]# 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

• 查看gc

root:/# jstat -gcutil 1 1000 5
  S0     S1     E      O      M     CCS    YGC     YGCT    FGC    FGCT     GCT
  0.00  18.57  22.58  42.71  93.54  90.85  22329  318.467     8    2.910  321.377
  0.00  18.57  41.78  42.71  93.54  90.85  22329  318.467     8    2.910  321.377
  0.00  18.57  62.83  42.71  93.54  90.85  22329  318.467     8    2.910  321.377

• 查看tcp连接数量

root:/# netstat -nat | awk '{print $6}' | sort | uniq -c | sort -n
      1 Foreign
      1 LISTEN
      1 established)
      2 CLOSE_WAIT
     16 TIME_WAIT
     88 ESTABLISHED

• 找到的线程ID转换为16进制格式

[[email protected] ~]# printf "%x\n" 6523
197b

• 打印线程的堆栈信息

[[email protected] ~]# 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)

• Analyze the thread's stack information

jstack 6515 > task.info
grep java.lang.Thread.State task.info |awk '{print $2$3$4$5}' |sort| uniq -c

• 执行jmapput the current heapdump下来

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

• 将dump.hprof文件使用VisualVM来打开

C:\Users\Administrator>jvisualvm

The launcher has determined that the parent process has a console and will reuse it for its own console output.
Closing the console will result in termination of the running program.
Use '--console suppress' to suppress console output.
Use '--console new' to create a separate console window.

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

其它方法

• 查看CPU信息 cat /proc/cpuinfo
• 查看内存信息 cat /proc/meminfo
• 查看Java线程数 ps -eLf | grep java -c
• 查看linux系统里打开文件描述符的最大值 ulimit -u
• found in the logTOP10的异常：grep ‘Exception’ /home/admin/logs/XX.log |awk -F':|,’ ‘{print $2}’|sort |uniq -c |sort -nr|head -10,You can use it after you find it-A 2 -B 2,Look at the front of the positioning log2line and the next two lines.