jmap

-heap 打印堆的概要信息命令：

1jmap -heap 7664

heap

各部分说明如下：

 1C:\Users\Administrator>jmap -heap 7664
 2Attaching to process ID 7664, please wait...
 3Debugger attached successfully.
 4Client compiler detected.
 5JVM version is 25.131-b11
 6
 7using thread-local object allocation.
 8Mark Sweep Compact GC
 9
10Heap Configuration:     ##JVM堆的配置参数
11   MinHeapFreeRatio         = 40
12   MaxHeapFreeRatio         = 70
13   MaxHeapSize              = 268435456 (256.0MB)   ##堆的最大大小
14   NewSize                  = 5570560 (5.3125MB)    ##新生代大小
15   MaxNewSize               = 89456640 (85.3125MB)  ##新生代最大大小
16   OldSize                  = 11206656 (10.6875MB)  ##老年代大小
17   NewRatio                 = 2                     ##新生代:老年代=1:2
18   SurvivorRatio            = 8                     ##Eden:2s = 8:2
19   MetaspaceSize            = 12582912 (12.0MB)    ##元空间的初始大小
20   CompressedClassSpaceSize = 1073741824 (1024.0MB)
21   MaxMetaspaceSize         = 314572800 (300.0MB)  ##元空间的最大大小
22   G1HeapRegionSize         = 0 (0.0MB)
23
24Heap Usage:  ##堆的实际使用情况
25New Generation (Eden + 1 Survivor Space):  ##新生代的使用情况，约18M
26   capacity = 17170432 (16.375MB)
27   used     = 15385488 (14.672744750976562MB)
28   free     = 1784944 (1.7022552490234375MB)
29   89.60454809756679% used
30Eden Space:  ##伊甸区
31   capacity = 15269888 (14.5625MB)
32   used     = 15269888 (14.5625MB)
33   free     = 0 (0.0MB)
34   100.0% used
35From Space:
36   capacity = 1900544 (1.8125MB)
37   used     = 115600 (0.1102447509765625MB)
38   free     = 1784944 (1.7022552490234375MB)
39   6.082469019396552% used
40To Space:
41   capacity = 1900544 (1.8125MB)
42   used     = 6264 (0.00597381591796875MB)
43   free     = 1894280 (1.8065261840820312MB)
44   0.32958984375% used
45tenured generation:  ##老年代的使用情况，约36M
46   capacity = 38060032 (36.296875MB)
47   used     = 35454608 (33.81214904785156MB)
48   free     = 2605424 (2.4847259521484375MB)
49   93.15443560320706% used
50
5120829 interned Strings occupying 2643456 bytes.

-dump 转储heap 命令：

1jmap  -dump:file=D:/a.phrof 7144

jstat

jstat命令可以查看堆内存各部分的使用量，以及加载类的数量。

-gc 垃圾回收的大小

1C:\Users\Administrator>jstat -gc 7044
2 S0C    S1C    S0U    S1U      EC       EU        OC         OU       MC     MU    CCSC   CCSU   YGC     YGCT    FGC    FGCT     GCT
31280.0 1280.0 116.9   0.0   10816.0   8653.0   26700.0    19417.7   52096.0 51394.9  0.0    0.0     2906    4.484   4      0.151    4.635

各个字段的含义如下：

S0C：第一个幸存区的大小
S1C：第二个幸存区的大小
S0U：第一个幸存区的使用大小
S1U：第二个幸存区的使用大小
EC：伊甸园区的大小
EU：伊甸园区的使用大小
OC：老年代大小
OU：老年代使用大小
MC：方法区大小
MU：方法区使用大小
CCSC:压缩类空间大小
CCSU:压缩类空间使用大小
YGC：年轻代垃圾回收次数
YGCT：年轻代垃圾回收消耗时间
FGC：老年代垃圾回收次数
FGCT：老年代垃圾回收消耗时间
GCT：垃圾回收消耗总时间

jcmd

JDK7后新增的命令，查看JVM内存的信息，很有用。

jcmd -l 查看所有的java进程，同jps命令。

1C:\Users\Administrator>jcmd -l
25216
37044 test.metaspace.TestMetaSpace
4740 org.jetbrains.idea.maven.server.RemoteMavenServer
5872 sun.tools.jcmd.JCmd -l
64972 org.jetbrains.jps.cmdline.Launcher C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/jgoodies-forms.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/jps-builders-6.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/oromatcher.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/javac2.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/slf4j-api-1.7.10.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/annotations.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/util.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/httpclient-4.5.2.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/snappy-in-java-0.5.1.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/aether-dependency-resolver.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/jdom.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/resources_en.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/lib/protobuf-java-2.5.0.jar;C:/Program Files/JetBrains/IntelliJ IDEA 2017.3.7/

jcmd PID help 查看帮助信息

 1C:\Users\Administrator>jcmd 7044 help
 27044:
 3The following commands are available:
 4JFR.stop
 5JFR.start
 6JFR.dump
 7JFR.check
 8VM.native_memory
 9VM.check_commercial_features
10VM.unlock_commercial_features
11ManagementAgent.stop
12ManagementAgent.start_local
13ManagementAgent.start
14GC.rotate_log
15Thread.print
16GC.class_stats
17GC.class_histogram
18GC.heap_dump
19GC.run_finalization
20GC.run
21VM.uptime
22VM.flags
23VM.system_properties
24VM.command_line
25VM.version
26help

jcmd PID VM.uptime 运行时间

1C:\Users\Administrator>jcmd 4236 VM.uptime
24236:
317.314 s

jcmd PID VM.flags 查看你JVM的启动参数

1C:\Users\Administrator>jcmd 4236 VM.flags
24236:
3-XX:InitialHeapSize=16777216 -XX:MaxHeapSize=268435456 -XX:MaxMetaspaceSize=314572800 -XX:MaxNewSize=89456640 -XX:MinHeapDeltaBytes=131072 -XX:NewSize=5570560 -XX:OldSize=11206656 -XX:+UseFastUnorderedTimeStamps -XX:-UseLargePagesIndividualAllocation

jcmd pid PerfCounter.print 查看性能统计

 1C:\Users\Administrator>jcmd 4236 PerfCounter.print
 24236:
 3java.ci.totalTime=2222906
 4java.cls.loadedClasses=33926
 5java.cls.sharedLoadedClasses=534
 6java.cls.sharedUnloadedClasses=0
 7java.cls.unloadedClasses=0
 8java.property.java.class.path="C:\Program Files\Java\jdk1.8.0_131\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\access-bridge.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_131\j"
 9java.property.java.endorsed.dirs="C:\Program Files\Java\jdk1.8.0_131\jre\lib\endorsed"
10java.property.java.ext.dirs="C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext;C:\WINDOWS\Sun\Java\lib\ext"
11java.property.java.home="C:\Program Files\Java\jdk1.8.0_131\jre"
12java.property.java.library.path="C:\Program Files\Java\jdk1.8.0_131\bin;C:\WINDOWS\Sun\Java\bin;C:\WINDOWS\system32;C:\WINDOWS;C:\Program Files\Java\jdk1.8.0_131\bin;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\WINDOWS\System32\OpenSSH\;C:\Users\Administrator\AppData\Local\Microsoft\WindowsApps;;."
13java.property.java.version="1.8.0_131"
14java.property.java.vm.info="mixed mode, sharing"
15java.property.java.vm.name="Java HotSpot(TM) Client VM"
16java.property.java.vm.specification.name="Java Virtual Machine Specification"
17java.property.java.vm.specification.vendor="Oracle Corporation"
18java.property.java.vm.specification.version="1.8"
19java.property.java.vm.vendor="Oracle Corporation"
20java.property.java.vm.version="25.131-b11"

jcmd PID GC.class_histogram 查看进程中类的统计信息

 1C:\Users\Administrator>jcmd 4236 GC.class_histogram
 24236:
 3
 4 num     #instances         #bytes  class name
 5----------------------------------------------
 6   1:        196631       17303528  java.lang.reflect.Method
 7   2:         89900       12060616  [C
 8   3:         43517        6228224  java.lang.Class
 9   4:        341415        5462640  net.sf.cglib.core.Signature
10   5:        170676        5461632  net.sf.cglib.proxy.MethodProxy
11   6:        170676        5461632  net.sf.cglib.proxy.MethodProxy$CreateInfo
12   7:          5128        4841296  [I
13   8:         86027        4803360  [Ljava.lang.Object;
14   9:         89749        1435984  java.lang.String
15  10:        171157        1369256  java.lang.Object
16  11:         42785        1369120  java.lang.ref.SoftReference
17  12:         42674        1365568  java.lang.ThreadLocal$ThreadLocalMap$Entry
18  13:         42994        1031856  java.util.HashMap$Node
19  14:         42675         682800  java.lang.ThreadLocal
20  15:         28446         474960  [Ljava.lang.Class;
21  16:            34         266336  [Ljava.util.HashMap$Node;
22  17:             2         262240  [Ljava.lang.ThreadLocal$ThreadLocalMap$Entry;

jcmd PID Thread.print 查看线程的堆栈信息

 1C:\Users\Administrator>jcmd 4236 Thread.print
 24236:
 32020-02-03 17:03:02
 4Full thread dump Java HotSpot(TM) Client VM (25.131-b11 mixed mode, sharing):
 5
 6"Service Thread" #8 daemon prio=9 os_prio=0 tid=0x0213d400 nid=0x19cc runnable [0x00000000]
 7   java.lang.Thread.State: RUNNABLE
 8
 9"C1 CompilerThread0" #7 daemon prio=9 os_prio=2 tid=0x02139000 nid=0x1b9c waiting on condition [0x00000000]
10   java.lang.Thread.State: RUNNABLE
11
12"Monitor Ctrl-Break" #6 daemon prio=5 os_prio=0 tid=0x14df9c00 nid=0x1d54 runnable [0x1500f000]
13   java.lang.Thread.State: RUNNABLE
14        at java.net.SocketInputStream.socketRead0(Native Method)
15        at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
16        at java.net.SocketInputStream.read(SocketInputStream.java:171)
17        at java.net.SocketInputStream.read(SocketInputStream.java:141)
18        at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
19        at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
20        at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
21        - locked <0x097afce0> (a java.io.InputStreamReader)
22        at java.io.InputStreamReader.read(InputStreamReader.java:184)
23        at java.io.BufferedReader.fill(BufferedReader.java:161)
24        at java.io.BufferedReader.readLine(BufferedReader.java:324)
25        - locked <0x097afce0> (a java.io.InputStreamReader)
26        at java.io.BufferedReader.readLine(BufferedReader.java:389)
27        at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:64)
28
29"Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x020df000 nid=0x8f8 waiting on condition [0x00000000]
30   java.lang.Thread.State: RUNNABLE
31
32"Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x020dd400 nid=0x1c04 runnable [0x00000000]
33   java.lang.Thread.State: RUNNABLE
34
35"Finalizer" #3 daemon prio=8 os_prio=1 tid=0x020c0c00 nid=0x7cc in Object.wait() [0x14cbf000]
36   java.lang.Thread.State: WAITING (on object monitor)
37        at java.lang.Object.wait(Native Method)
38        - waiting on <0x097b01b0> (a java.lang.ref.ReferenceQueue$Lock)
39        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
40        - locked <0x097b01b0> (a java.lang.ref.ReferenceQueue$Lock)
41        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
42        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)
43
44"Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x02067000 nid=0x728 in Object.wait() [0x041df000]
45   java.lang.Thread.State: WAITING (on object monitor)
46        at java.lang.Object.wait(Native Method)
47        - waiting on <0x097b0350> (a java.lang.ref.Reference$Lock)
48        at java.lang.Object.wait(Object.java:502)
49        at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
50        - locked <0x097b0350> (a java.lang.ref.Reference$Lock)
51        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
52
53"main" #1 prio=5 os_prio=0 tid=0x00adc800 nid=0x174c runnable [0x01a4f000]
54   java.lang.Thread.State: RUNNABLE
55        at java.lang.String.equals(String.java:990)
56        at java.util.HashMap.getNode(HashMap.java:571)
57        at java.util.HashMap.containsKey(HashMap.java:595)
58        at java.util.HashSet.contains(HashSet.java:203)
59        at net.sf.cglib.core.AbstractClassGenerator$ClassLoaderData$1.evaluate(AbstractClassGenerator.java:78)
60        at net.sf.cglib.core.DefaultNamingPolicy.getClassName(DefaultNamingPolicy.java:51)
61        at net.sf.cglib.core.AbstractClassGenerator.generateClassName(AbstractClassGenerator.java:157)
62        at net.sf.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:320)
63        - locked <0x097915f0> (a sun.misc.Launcher$AppClassLoader)
64        at net.sf.cglib.proxy.Enhancer.generate(Enhancer.java:492)
65        at net.sf.cglib.core.AbstractClassGenerator$ClassLoaderData.get(AbstractClassGenerator.java:117)
66        at net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:294)
67        at net.sf.cglib.proxy.Enhancer.createHelper(Enhancer.java:480)
68        at net.sf.cglib.proxy.Enhancer.create(Enhancer.java:305)
69        at test.metaspace.TestMetaSpace.main(TestMetaSpace.java:23)
70
71"VM Thread" os_prio=2 tid=0x02062c00 nid=0x1eac runnable
72
73"VM Periodic Task Thread" os_prio=2 tid=0x14e73000 nid=0x1198 waiting on condition
74
75JNI global references: 124

jcmd PID GC.heap_dump fileName 堆的转储

1C:\Users\Administrator>jcmd 4236 GC.heap_dump  d:/aa.hprof
24236:
3Heap dump file created

jcmd PID VM.system_properties 查看JVM的系统属性
jcmd PID VM.version 查看JVM的版本信息

1C:\Users\Administrator>jcmd 2472 VM.version
22472:
3Java HotSpot(TM) Client VM version 25.131-b11
4JDK 8.0_131

jcmd PID VM.command_line 查看JVM的命令行参数

1C:\Users\Administrator>jcmd 2472 VM.command_line
22472:
3VM Arguments:
4jvm_args: -XX:MaxMetaspaceSize=300m -javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2017.3.7\lib\idea_rt.jar=53002:C:\Program Files\JetBrains\IntelliJ IDEA 2017.3.7\bin -Dfile.encoding=UTF-8
5java_command: test.metaspace.TestMetaSpace
6java_class_path (initial): C:\Program Files\Java\jdk1.8.0_131\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\access-bridge.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\rt.jar;D:\develop\IdeaProjects\learning\test01\target\classes;D:\develop\maven_repo\io\netty\netty-all\4.1.0.Final\netty-all-4.1.0.Final.jar;D:\develop\maven_repo\cglib\cglib\3.2.10\cglib-3.2.10.jar;D:\develop\maven_repo\org\ow2\asm\asm\7.0\asm-7.0.jar;D:\develop\maven_repo\org\apache\ant\ant\1.10.3\ant-1.10.3.jar;D:\develop\maven_repo\org\apache\ant\ant-launcher\1.10.3\ant-launcher-1.10.3.jar;C:\Program Files\JetBrains\IntelliJ IDEA 2017.3.7\lib\idea_rt.jar
7Launcher Type: SUN_STANDARD

jstack

专门查看线程堆栈信息。命令：jstack PID 同jscmd PID Thread.print

 1C:\Users\Administrator>jstack 2472
 22020-02-03 17:19:21
 3Full thread dump Java HotSpot(TM) Client VM (25.131-b11 mixed mode):
 4
 5"Service Thread" #8 daemon prio=9 os_prio=0 tid=0x14d4b800 nid=0x18b0 runnable [0x00000000]
 6   java.lang.Thread.State: RUNNABLE
 7
 8"C1 CompilerThread0" #7 daemon prio=9 os_prio=2 tid=0x14d4a800 nid=0x1de0 waiting on condition [0x00000000]
 9   java.lang.Thread.State: RUNNABLE
10
11"Monitor Ctrl-Break" #6 daemon prio=5 os_prio=0 tid=0x14d4a000 nid=0x1d9c runnable [0x14faf000]
12   java.lang.Thread.State: RUNNABLE
13        at java.net.SocketInputStream.socketRead0(Native Method)
14        at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
15        at java.net.SocketInputStream.read(SocketInputStream.java:171)
16        at java.net.SocketInputStream.read(SocketInputStream.java:141)
17        at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
18        at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
19        at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
20        - locked <0x09da3e70> (a java.io.InputStreamReader)

MBC 图形化JVM工具

JVM自带的一个内存分析工具，类似Jvisualvm

jhat

jhat 转储文件路径 jhat用于解析转储文件hprof

OQL

对象查询语言

JVM Learn 17 JVM内存排查相关命令用法