JVM信息查看

shixinzhang 發(fā)布于2019-08-14 15:20 / 1218人閱讀

摘要：系列垃圾回收基礎(chǔ)的編譯策略的三大基礎(chǔ)算法的三大高級(jí)算法策略的評(píng)價(jià)指標(biāo)信息查看通用日志解讀的數(shù)據(jù)結(jié)構(gòu)類初始化順序?qū)ο蠼Y(jié)構(gòu)及大小計(jì)算的類加載機(jī)制對(duì)象分配簡要流程年老代過大有什么影響空間溢出實(shí)例關(guān)于線程與序本文主要講述如何查看應(yīng)用的信息。

jvm系列

垃圾回收基礎(chǔ)

JVM的編譯策略

GC的三大基礎(chǔ)算法

GC的三大高級(jí)算法

GC策略的評(píng)價(jià)指標(biāo)

JVM信息查看

GC通用日志解讀

jvm的card table數(shù)據(jù)結(jié)構(gòu)

Java類初始化順序

Java對(duì)象結(jié)構(gòu)及大小計(jì)算

Java的類加載機(jī)制

Java對(duì)象分配簡要流程

年老代過大有什么影響

Survivor空間溢出實(shí)例

關(guān)于Object=null

Java線程與Xss

序

本文主要講述如何查看java應(yīng)用的jvm信息。

1、查看所有參數(shù) jinfo -flags pid

Java -XX:+PrintCommandLineFlags 這個(gè)參數(shù)的作用是顯示出VM初始化完畢后所有跟最初的默認(rèn)值不同的參數(shù)及它們的值。（JDK5以上支持）

-XX:+PrintFlagsFinal顯示所有可設(shè)置的參數(shù)及它們的值（ JDK 6 update 21開始才可以用），默認(rèn)是不包括diagnostic或experimental系的。要在-XX:+PrintFlagsFinal的輸出里看到這兩種參數(shù)的信息，分別需要顯式指定-XX:+UnlockDiagnosticVMOptions / -XX:+UnlockExperimentalVMOptions

-XX:+PrintFlagsInitial看下所有XX參數(shù)的默認(rèn)值，也可以通過-XX:+PrintFlagsFinal進(jìn)行對(duì)比出修改過的參數(shù)，當(dāng)然通過-XX:+PrintCommandLineFlags就可以自動(dòng)顯示出修改過的值

jinfo -flags pid

[xixicat@cloud01 ~]$ jps 
9275 Jps
22855 start.jar
22869 XmlConfiguration
20967 Application
[xixicat@cloud01 ~]$ jinfo -flags 22869
Attaching to process ID 22869, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 23.21-b01
-javaagent:/opt/xixicat/apps/lib/jolokia-jvm-1.1.0-agent.jar=port=23061 -Xloggc:/var/xixicat/logs/app.gc.log.201504301631 -XX:ErrorFile=/var/xixicat/logs/app.vmerr.log.201504301631 -XX:HeapDumpPath=/var/xixicat/logs/app.heaperr.log.201504301631 -Xmx5g -Xms5g -XX:MaxPermSize=256m -XX:+HeapDumpOnOutOfMemoryError -XX:+DisableExplicitGC -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps -XX:+PrintGCApplicationStoppedTime -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution -XX:+PrintCommandLineFlags -XX:+PrintAdaptiveSizePolicy -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:MaxGCPauseMillis=100 -XX:StringTableSize=49999 -Djetty.home=/opt/xixicat/apps/server/jetty-distribution-8.1.9.v20130131 -Dapp.port=8061 -Dmedis_environment=online -Dcore.step=app -DSTOP.PORT=38061 -Djetty.port=8061 -Dcom.sun.management.jmxremote.authenticate=false -Dapp.logdir=/var/xixicat/logs -DLog4jContextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector -Dapp.ip=10.64.28.207 -Dapp.context -Dcom.sun.management.jmxremote.ssl=false -Djetty.context -Djava.io.tmpdir=/tmp -Djetty.host=cloud01 -Djava.net.preferIPv6Addresses=false -DSTOP.KEY=stop_app -Dcore.zookeeper=127.0.0.1:9331 -Djetty.logs=/var/xixicat/logs -Dapp.workdir=/opt/xixicat/apps/app/work -Dapp.key=app -Dfile.encoding=UTF-8 -Dapp.host=cloud01 -Duser.timezone=GMT+08 -Djetty.appkey=app -DAsyncLogger.WaitStrategy=Block -Dcom.sun.management.jmxremote.port=8199 -Djetty.home=/opt/xixicat/apps/server/jetty-distribution-8.1.9.v20130131 -Denvironment=online

2、查看可用jinfo -flag修改的Java參數(shù)

java -XX:+PrintFlagsFinal -version |grep manageable
通過選項(xiàng)-XX:+PrintFlagsFinal可以列出所有的JVM flag，而其中的標(biāo)注為manageable 的flag則是值得我們關(guān)注的部分。這些flag可通過JDK management interface（-XX:+PrintFlagsFinal）動(dòng)態(tài)修改。

-XX:+PrintGCDetails

jinfo -flag -PrintGCDetails 12278

3、jmap -heap pid 查看目前堆情況

[xixicat@cloud01 ~]$ jmap -heap 22869
Attaching to process ID 22869, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 23.21-b01
using thread-local object allocation.
Garbage-First (G1) GC with 4 thread(s)
Heap Configuration:
   MinHeapFreeRatio = 40
   MaxHeapFreeRatio = 70
   MaxHeapSize      = 5368709120 (5120.0MB)
   NewSize          = 1363144 (1.2999954223632812MB)
   MaxNewSize       = 17592186044415 MB
   OldSize          = 5452592 (5.1999969482421875MB)
   NewRatio         = 2
   SurvivorRatio    = 8
   PermSize         = 20971520 (20.0MB)
   MaxPermSize      = 268435456 (256.0MB)
   G1HeapRegionSize = 2097152 (2.0MB)
Heap Usage:
G1 Heap:
   regions  = 2560
   capacity = 5368709120 (5120.0MB)
   used     = 3826721792 (3649.4462890625MB)
   free     = 1541987328 (1470.5537109375MB)
   71.27824783325195% used
G1 Young Generation:
Eden Space:
   regions  = 1068
   capacity = 2808086528 (2678.0MB)
   used     = 2239758336 (2136.0MB)
   free     = 568328192 (542.0MB)
   79.76101568334578% used
Survivor Space:
   regions  = 29
   capacity = 60817408 (58.0MB)
   used     = 60817408 (58.0MB)
   free     = 0 (0.0MB)
   100.0% used
G1 Old Generation:
   regions  = 1000
   capacity = 2499805184 (2384.0MB)
   used     = 1524048896 (1453.4462890625MB)
   free     = 975756288 (930.5537109375MB)
   60.96670675597735% used
Perm Generation:
   capacity = 171966464 (164.0MB)
   used     = 170752872 (162.8426284790039MB)
   free     = 1213592 (1.1573715209960938MB)
   99.29428565792921% used
48213 interned Strings occupying 5246936 bytes.

4、jmap -histo:live pid | head -7

查看對(duì)象分布

5、jcmd pid VM.flags

[xixicat@cloud01 ~]$ jcmd 15308 VM.flags
15308:
-XX:+DisableExplicitGC -XX:ErrorFile=/var/xixicat/logs/app.vmerr.log.201505071655 -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/var/xixicat/logs/app.heaperr.log.201505071655 -XX:InitialHeapSize=5368709120 -XX:+ManagementServer -XX:MaxGCPauseMillis=100 -XX:MaxHeapSize=5368709120 -XX:MaxPermSize=268435456 -XX:+PrintAdaptiveSizePolicy -XX:+PrintCommandLineFlags -XX:+PrintGC -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCDateStamps -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution -XX:StringTableSize=49999 -XX:+UnlockExperimentalVMOptions -XX:+UseCompressedOops -XX:+UseG1GC