1.jps (Java Virtual Machine Process Status Tool)
用來檢視基于HotSpot的JVM裡面中,所有具有通路權限的Java程序的具體狀态, 包括程序ID,程序啟動的路徑及啟動參數等等,與unix上的ps類似,隻不過jps是用來顯示java程序,可以把jps了解為ps的一個子集。
jps [options] [hostid]
如果不指定hostid就預設為目前主機或伺服器;如果指定了hostid,它就會顯示指定hostid上面的java程序,不過這需要遠端服務上開啟了jstatd服務。
-q:忽略輸出的類名、Jar名以及傳遞給main方法的參數,隻輸出pid。
-m:輸出傳遞給main方法的參數,如果是内嵌的JVM則輸出為null。
-l:輸出完全的包名,應用主類名,jar的完全路徑名
-v:輸出傳給jvm的參數
-V:輸出通過标記的檔案傳遞給JVM的參數(.hotspotrc檔案,或者是通過參數-XX:Flags=指定的檔案)。
-J 用于傳遞jvm選項到由javac調用的java加載器中,例如,“-J-Xms48m”将把啟動記憶體設定為48M,使用-J選項可以非常友善的向基于Java的開發的底層虛拟機應用程式傳遞參數。
jps -mlv
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9680 org.jetbrains.idea.maven.server.RemoteMavenServer -Djava.awt.headless=true -Didea.version==2017.1.1 -Xmx768m -Didea.maven.embedder.version=3.2.5 -Dfile.encoding=GBK
-
2356 org.jetbrains.jps.cmdline.Launcher C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/openapi.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/jgoodies-forms.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/javac2.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/idea_rt.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/jna-platform.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/netty-all-4.1.9.Final.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/protobuf-2.5.0.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/annotations.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/trove4j.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/nanoxml-2.2.3.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/forms_rt.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/jdom.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/asm-all.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/lib/jps-model.jar;C:/Program Files/JetBra -Xmx700m -Djava.awt.headless=true -Djava.endorsed.dirs="" -Djdt.compiler.useSingleThread=true -Dcompile.parallel=false -Drebuild.on.dependency.change=true -Djava.net.preferIPv4Stack=true -Dio.netty.initialSeedUniquifier=-8384703316530083662 -Dfile.encoding=GBK -Djps.file.types.component.name=FileTypeManager -Duser.language=zh -Duser.country=CN -Didea.paths.selector=IntelliJIdea2017.1 -Didea.home.path=C:\Program Files\JetBrains\IntelliJ IDEA 2017.1.1 -Didea.config.path=C:\Users\vincent\.IntelliJIdea2017.1\config -Didea.plugins.path=C:\Users\vincent\.IntelliJIdea2017.1\config\plugins -Djps.log.dir=C:/Users/vincent/.IntelliJIdea2017.1/system/log/build-log -Djps.fallback.jdk.home=C:/Program Files/JetBrains/IntelliJ IDEA 2017.1.1/jre64 -Djps.fallback.jdk.version=1.8.0_112-release -Dio.netty.noUnsafe=true -Djava.io.tmpdir=C:/Users/vincent/.IntelliJIdea2017.1/system/compile-server/es-demo_7a0f3d0f/_temp_ -Djps.backward.ref.index.builder=true -Dkotlin.incremental.compilation.experimental=true -Dkotlin.daemon.enabled
-
4116 -Xms128m -Xmx750m -XX:ReservedCodeCacheSize=240m -XX:+UseConcMarkSweepGC -XX:SoftRefLRUPolicyMSPerMB=50 -ea -Dsun.io.useCanonCaches=false -Djava.net.preferIPv4Stack=true -XX:+HeapDumpOnOutOfMemoryError -XX:-OmitStackTraceInFastThrow -Djb.vmOptionsFile=C:\Program Files\JetBrains\IntelliJ IDEA 2017.1.1\bin\idea64.exe.vmoptions -Xbootclasspath/a:C:\Program Files\JetBrains\IntelliJ IDEA 2017.1.1\lib\boot.jar -Didea.jre.check=true -Didea.paths.selector=IntelliJIdea2017.1 -XX:ErrorFile=C:\Users\vincent\java_error_in_idea_%p.log -XX:HeapDumpPath=C:\Users\vincent\java_error_in_idea.hprof
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16776 sun.tools.jps.Jps -mlv -Denv.class.path=.;D:\jdk\lib\dt.jar;D:\jdk\lib\tools.jar; -Dapplication.home=D:\jdk -Xms8m
2. jstack
jstack主要用來檢視某個Java程序内的線程堆棧資訊。
jstack [option] pid
jstack [option] executable core
jstack [option] [server-id@]remote-hostname-or-ip
-l long listings,會列印出額外的鎖資訊,在發生死鎖時可以用<strong>jstack -l pid</strong>來觀察鎖持有情況
-m mixed mode,不僅會輸出Java堆棧資訊,還會輸出C/C++堆棧資訊(比如Native方法)
jstack可以定位到線程堆棧,根據堆棧資訊我們可以定位到具體代碼,是以它在JVM性能調優中使用得非常多。下面我們來一個執行個體找出某個Java程序中最耗費CPU的Java線程并定位堆棧資訊,用到的指令有ps、top、printf、jstack、grep。
第一步: 先找出Java程序ID,伺服器上的Java應用名稱為wordcount.jar:
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root@ubuntu:/# ps -ef | grep mrf-center | grep -v grep
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root 21711 1 1 14:47 pts/3 00:02:10 java -jar mrf-center.jar
得到程序ID為21711,第二步找出該程序内最耗費CPU的線程,可以使用ps -Lfp pid或者ps -mp pid -o THREAD, tid, time或者top -Hp pid,我這裡用第三個,輸出如下:
![](https://img.laitimes.com/img/_0nNw4CM6IyYiwiM6ICdiwiI0gTMx81dsQWZ4lmZf1GLlpXazVmcvwFciV2dsQXYtJ3bm9CX9s2RkBnVHFmb1clWvB3MaVnRtp1XlBXe0xCMy81dvRWYoNHLwEzX5xCMx8FesU2cfdGLwMzX0xiRGZkRGZ0Xy9GbvNGLpZTY1EmMZVDUSFTU4VFRR9Fd4VGdsYTMfVmepNHLrJXYtJXZ0F2dvwVZnFWbp1zczV2YvJHctM3cv1Ce-cmbw5SO1cTO2MGOjFWOlJ2NjdzYyYzX2ITO1MTM4AzLcdDMyIDMy8CXn9Gbi9CXzV2Zh1WavwVbvNmLvR3YxUjLyM3Lc9CX6MHc0RHaiojIsJye.png)
TIME列就是各個Java線程耗費的CPU時間,CPU時間最長的是線程ID為21742的線程,用
printf "%x\n" 21742
得到21742的十六進制值為54ee,下面會用到。
OK,下一步終于輪到jstack上場了,它用來輸出程序21711的堆棧資訊,然後根據線程ID的十六進制值grep,如下:
root@ubuntu:/# jstack 21711 | grep 54ee
"PollIntervalRetrySchedulerThread" prio=10 tid=0x00007f950043e000 nid=0x54ee in Object.wait() [0x00007f94c6eda000]
可以看到CPU消耗在PollIntervalRetrySchedulerThread這個類的Object.wait(),我找了下我的代碼,定位到下面的代碼。
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// Idle wait
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getLog().info("Thread [" + getName() + "] is idle waiting...");
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schedulerThreadState = PollTaskSchedulerThreadState.IdleWaiting;
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long now = System.currentTimeMillis();
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long waitTime = now + getIdleWaitTime();
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long timeUntilContinue = waitTime - now;
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synchronized(sigLock) {
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try {
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if(!halted.get()) {
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sigLock.wait(timeUntilContinue);
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}
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}
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catch (InterruptedException ignore) {
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}
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}
它是輪詢任務的空閑等待代碼,上面的sigLock.wait(timeUntilContinue)就對應了前面的Object.wait()。
3. jmap(Memory Map)和jhat(Java Heap Analysis Tool)
jmap用來檢視堆記憶體使用狀況,一般結合jhat使用。
jmap文法格式如下:
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jmap [option] pid
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jmap [option] executable core
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jmap [option] [server-id@]remote-hostname-or-ip
如果運作在64位JVM上,可能需要指定-J-d64指令選項參數。
(1) 列印程序的類加載器和類加載器加載的持久代對象資訊,輸出:類加載器名稱、對象是否存活(不可靠)、對象位址、父類加載器、已加載的類大小等資訊,如下圖:
jmap -permstat pid
(2) 使用jmap -heap pid檢視程序堆記憶體使用情況,包括使用的GC算法、堆配置參數和各代中堆記憶體使用情況。比如下面的例子:
jmap -heap pid
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[root@storm-master home]# jmap -heap 2860
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Attaching to process ID 2860, please wait...
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Debugger attached successfully.
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Server compiler detected.
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JVM version is 20.45-b01
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using thread-local object allocation.
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Mark Sweep Compact GC
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Heap Configuration:
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MinHeapFreeRatio = 40
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MaxHeapFreeRatio = 70
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MaxHeapSize = 257949696 (246.0MB)
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NewSize = 1310720 (1.25MB)
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MaxNewSize = 17592186044415 MB
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OldSize = 5439488 (5.1875MB)
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NewRatio = 2
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SurvivorRatio = 8
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PermSize = 21757952 (20.75MB)
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MaxPermSize = 85983232 (82.0MB)
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Heap Usage:
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New Generation (Eden + 1 Survivor Space):
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capacity = 12189696 (11.625MB)
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used = 6769392 (6.4557952880859375MB)
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free = 5420304 (5.1692047119140625MB)
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55.53372290826613% used
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Eden Space:
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capacity = 10878976 (10.375MB)
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used = 6585608 (6.280525207519531MB)
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free = 4293368 (4.094474792480469MB)
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60.53518272307982% used
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From Space:
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capacity = 1310720 (1.25MB)
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used = 183784 (0.17527008056640625MB)
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free = 1126936 (1.0747299194335938MB)
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14.0216064453125% used
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To Space:
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capacity = 1310720 (1.25MB)
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used = 0 (0.0MB)
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free = 1310720 (1.25MB)
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0.0% used
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tenured generation:
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capacity = 26619904 (25.38671875MB)
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used = 15785896 (15.054603576660156MB)
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free = 10834008 (10.332115173339844MB)
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59.30110040967841% used
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Perm Generation:
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capacity = 33554432 (32.0MB)
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used = 33323352 (31.779624938964844MB)
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free = 231080 (0.22037506103515625MB)
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99.31132793426514% used
(3)檢視堆記憶體中的對象數目、大小統計直方圖,如果帶上live則隻統計活對象:
jmap -histo[:live] pid
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root@ubuntu:/# jmap -histo:live 21711 | more
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num #instances #bytes class name
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----------------------------------------------
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1: 38445 5597736 <constMethodKlass>
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2: 38445 5237288 <methodKlass>
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3: 3500 3749504 <constantPoolKlass>
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4: 60858 3242600 <symbolKlass>
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5: 3500 2715264 <instanceKlassKlass>
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6: 2796 2131424 <constantPoolCacheKlass>
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7: 5543 1317400 [I
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8: 13714 1010768 [C
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9: 4752 1003344 [B
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10: 1225 639656 <methodDataKlass>
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11: 14194 454208 java.lang.String
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12: 3809 396136 java.lang.Class
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13: 4979 311952 [S
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14: 5598 287064 [[I
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15: 3028 266464 java.lang.reflect.Method
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16: 280 163520 <objArrayKlassKlass>
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17: 4355 139360 java.util.HashMap$Entry
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18: 1869 138568 [Ljava.util.HashMap$Entry;
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19: 2443 97720 java.util.LinkedHashMap$Entry
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20: 2072 82880 java.lang.ref.SoftReference
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21: 1807 71528 [Ljava.lang.Object;
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22: 2206 70592 java.lang.ref.WeakReference
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23: 934 52304 java.util.LinkedHashMap
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24: 871 48776 java.beans.MethodDescriptor
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25: 1442 46144 java.util.concurrent.ConcurrentHashMap$HashEntry
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26: 804 38592 java.util.HashMap
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27: 948 37920 java.util.concurrent.ConcurrentHashMap$Segment
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28: 1621 35696 [Ljava.lang.Class;
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29: 1313 34880 [Ljava.lang.String;
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30: 1396 33504 java.util.LinkedList$Entry
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31: 462 33264 java.lang.reflect.Field
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32: 1024 32768 java.util.Hashtable$Entry
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33: 948 31440 [Ljava.util.concurrent.ConcurrentHashMap$HashEntry;
class name是對象類型,說明如下:
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B byte
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C char
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D double
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F float
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I int
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J long
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Z boolean
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[ 數組,如[I表示int[]
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[L+類名 其他對象
還有一個很常用的情況是:用jmap把程序記憶體使用情況dump到檔案中,再用jhat分析檢視。jmap進行dump指令格式如下:
jmap -dump:format=b,file=dumpFileName
一樣地對上面程序ID為21711進行Dump:
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root@ubuntu:/# jmap -dump:format=b,file=/tmp/dump.dat 21711
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Dumping heap to /tmp/dump.dat ...
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Heap dump file created
dump出來的檔案可以用MAT、VisualVM等工具檢視,這裡用jhat檢視:
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root@ubuntu:/# jhat -port 9998 /tmp/dump.dat
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Reading from /tmp/dump.dat...
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Dump file created Tue Jan 28 17:46:14 CST 2014
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Snapshot read, resolving...
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Resolving 132207 objects...
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Chasing references, expect 26 dots..........................
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Eliminating duplicate references..........................
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Snapshot resolved.
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Started HTTP server on port 9998
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Server is ready.
然後就可以在浏覽器中輸入主機位址:9998檢視了:
4.jstat(JVM統計監測工具)
看看各個區記憶體和GC的情況
stat [ generalOption | outputOptions vmid [interval[s|ms] [count]] ]
vmid是Java虛拟機ID,在Linux/Unix系統上一般就是程序ID。interval是采樣時間間隔。count是采樣數目。比如下面輸出的是GC資訊,采樣時間間隔為250ms,采樣數為6:
[root@storm-master Desktop]# jstat -gc 2860 250 6
S0C、S1C、S0U、S1U:Survivor 0/1區容量(Capacity)和使用量(Used)
EC、EU:Eden區容量和使用量
OC、OU:年老代容量和使用量
PC、PU:永久代容量和使用量
YGC、YGT:年輕代GC次數和GC耗時
FGC、FGCT:Full GC次數和Full GC耗時
GCT:GC總耗時
5.jinfo
jinfo是jdk自帶的指令,用來檢視jvm的配置參數。通常會先使用jps檢視java程序的id,然後使用jinfo檢視指定pid的jvm資訊
jinfo -flags process_id
jps
4704 Launcher
9680 RemoteMavenServer
4116
13052 Jps
jinfo -flags 9680
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Debugger attached successfully.
-
Server compiler detected.
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JVM version is 25.91-b15
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Non-default VM flags: -XX:CICompilerCount=4 -XX:InitialHeapSize=268435456 -XX:MaxHeapSize=805306368 -XX:MaxNewSize=268435456 -XX:MinHeapDeltaBytes=524288 -XX:NewSize=89128960 -XX:OldSize=179306496 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseFastUnorderedTimeStamps -XX:-UseLargePagesIndividualAllocation -XX:+UseParallelGC
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Command line: -Djava.awt.headless=true -Didea.version==2017.1.1 -Xmx768m -Didea.maven.embedder.version=3.2.5 -Dfile.encoding=GBK
-
java -agentlib:hprof[=options] ToBeProfiledClass
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java -Xrunprof[:options] ToBeProfiledClass
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javac -J-agentlib:hprof[=options] ToBeProfiledClass
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Option Name and Value Description Default
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--------------------- ----------- -------
-
heap=dump|sites|all heap profiling all
-
cpu=samples|times|old CPU usage off
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monitor=y|n monitor contention n
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format=a|b text(txt) or binary output a
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file=<file> write data to file java.hprof[.txt]
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net=<host>:<port> send data over a socket off
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depth=<size> stack trace depth 4
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interval=<ms> sample interval in ms 10
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cutoff=<value> output cutoff point 0.0001
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lineno=y|n line number in traces? y
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thread=y|n thread in traces? n
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doe=y|n dump on exit? y
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msa=y|n Solaris micro state accounting n
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force=y|n force output to <file> y
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verbose=y|n print messages about dumps y