Jps jps 可以看到运行中的java进程
1 2 3 sh-4.2$ jps 370 xxx.jar 180682 Jps
Jcmd jcmd可以看到运行中的java进程以及参数
1 2 3 sh-4.2$ jcmd 370 /usr/local/xxx.jar config_path=xxx.yaml 180773 sun.tools.jcmd.JCmd
Jmap jmap是可以查看整个JVM内存的工具。
jmap -heap <pid>即可查看JVM堆堆使用情况，主要有两块，一块是Heap配置，另一块是Heap使用情况。
Heap配置中包含了最小堆空余空间比例、最大比例、最大堆大小、新生代大小、老生代大小、新生代比例、老生代比例、原空间大小等等。这部分是Java进程启动的时候由JVM参数决定的
Heap Usage是堆的使用情况，包括新生代使用情况、老生代使用情况（容量、使用、未使用）
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 sh-4.2$ jmap -heap 364 Attaching to process ID 364, please wait... Debugger attached successfully. Server compiler detected. JVM version is 25.252-b4 using thread-local object allocation. Parallel GC with 48 thread(s) Heap Configuration: MinHeapFreeRatio = 0 MaxHeapFreeRatio = 100 MaxHeapSize = 32210157568 (30718.0MB) NewSize = 715653120 (682.5MB) MaxNewSize = 10736369664 (10239.0MB) OldSize = 1431830528 (1365.5MB) NewRatio = 2 SurvivorRatio = 8 MetaspaceSize = 21807104 (20.796875MB) CompressedClassSpaceSize = 1073741824 (1024.0MB) MaxMetaspaceSize = 17592186044415 MB G1HeapRegionSize = 0 (0.0MB) Heap Usage: PS Young Generation Eden Space: capacity = 88604672 (84.5MB) used = 6212968 (5.925148010253906MB) free = 82391704 (78.5748519897461MB) 7.0120094795904215% used From Space: capacity = 9961472 (9.5MB) used = 1900544 (1.8125MB) free = 8060928 (7.6875MB) 19.07894736842105% used To Space: capacity = 9961472 (9.5MB) used = 0 (0.0MB) free = 9961472 (9.5MB) 0.0% used PS Old Generation capacity = 1482162176 (1413.5MB) used = 230906152 (220.20926666259766MB) free = 1251256024 (1193.2907333374023MB) 15.57900719226018% used 20563 interned Strings occupying 1939392 bytes.
jmap -histo <pid>可以查看JVM内存中每个类的内存使用情况
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 sh-4.2$ jmap -histo 370 | less num #instances #bytes class name ---------------------------------------------- 1: 1887996 284532232 [C 2: 51934 55537536 [I 3: 1368797 51696928 [B 4: 1686385 46376560 [Ljava.lang.Object; 5: 846166 33846640 java.util.TreeMap$Entry 6: 494971 23758608 java.util.TreeMap 7: 984173 23620152 java.lang.String 8: 349310 19561360 sun.nio.cs.UTF_8$Encoder 9: 495105 15843360 java.util.Collections$UnmodifiableMap 10: 494750 15832000 java.util.TreeMap$EntryIterator 11: 494925 11878200 java.util.Arrays$ArrayList 12: 473586 11366064 java.util.Collections$UnmodifiableMap$UnmodifiableEntrySet$1
jmap -finalizerinfo <pid>可以看到有多少个对象在等待finalizer
1 2 3 4 5 6 sh-4.2$ jmap -finalizerinfo 370 Attaching to process ID 370, please wait... Debugger attached successfully. Server compiler detected. JVM version is 25.252-b4 Number of objects pending for finalization: 0
jmap -dump:format=b,file=dump.bin 370 可以把堆中的数据导出到二进制文件中
1 2 3 4 sh-4.2$ jmap -dump:format=b,file=dump.bin 370 Heap dump file created sh-4.2$ ls dump.bin
Jstack jstack <pid>可以看到所有线程目前的栈信息。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 "Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007fd8506eb000 nid=0x1a7 in Object.wait() [0x00007fd77b826000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144) - locked <0x000000008023bb50> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216) "Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007fd8506de800 nid=0x1a6 in Object.wait() [0x00007fd77baf9000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) at java.lang.Object.wait(Object.java:502) at java.lang.ref.Reference.tryHandlePending(Reference.java:191) - locked <0x00000000802478a8> (a java.lang.ref.Reference$Lock) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153) "VM Thread" os_prio=0 tid=0x00007fd8506db000 nid=0x1a5 runnable "GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00007fd85001f000 nid=0x175 runnable "GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00007fd850021000 nid=0x176 runnable
Jstat options 查看options
1 2 3 4 5 6 7 8 9 10 11 12 13 sh-4.2$ jstat -options -class -compiler -gc -gccapacity -gccause -gcmetacapacity -gcnew -gcnewcapacity -gcold -gcoldcapacity -gcutil -printcompilation
类加载情况 查看类的个数, 每1000毫秒打印一次，一共打印10次
1 2 3 4 5 6 7 8 9 10 11 12 sh-4.2$ jstat -class 370 1000 10 Loaded Bytes Unloaded Bytes Time 12501 23290.5 0 0.0 9.15 12501 23290.5 0 0.0 9.15 12501 23290.5 0 0.0 9.15 12501 23290.5 0 0.0 9.15 12501 23290.5 0 0.0 9.15 12501 23290.5 0 0.0 9.15 12501 23290.5 0 0.0 9.15 12501 23290.5 0 0.0 9.15 12501 23290.5 0 0.0 9.15 12501 23290.5 0 0.0 9.15
JIT情况 查看JIT实时编译器编译的情况
1 2 3 4 5 sh-4.2$ jstat -compiler 370 1000 3 Compiled Failed Invalid Time FailedType FailedMethod 12448 5 0 68.28 1 io/netty/buffer/SizeClasses sizeClass 12448 5 0 68.28 1 io/netty/buffer/SizeClasses sizeClass 12448 5 0 68.28 1 io/netty/buffer/SizeClasses sizeClass
GC情况 查看GC情况，每一列分别对应
S0C
第一个survivor的容量
S1C
第二个survivor的容量
S0U
第一个survivor的使用空间
S1U
第二个survivor的使用空间
EC
eden容量
eden和survivor的比例是8:1:1
EU
eden使用空间
OC
老年代容量
OU
老年代使用空间
MC
方法区的容量
MU
方法区使用空间
CCSC
压缩类容量
注意被压缩的不是类，而是对象头中指向类的指针被压缩成32位了
CCSU
压缩类使用空间
YGC
YGC的次数
YGCT
YGC的时间
FGC
FULL GC的次数
FGCT
FULL GC的时间
GCT
GC总时间
1 2 3 4 5 sh-4.2$ jstat -gc 370 1000 3 S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT 1024.0 9728.0 576.0 0.0 485888.0 256731.1 1941504.0 60846.4 67968.0 64626.7 8576.0 7907.2 96 1.053 3 0.343 1.396 1024.0 9728.0 576.0 0.0 485888.0 299599.8 1941504.0 60846.4 67968.0 64626.7 8576.0 7907.2 96 1.053 3 0.343 1.396 1024.0 9728.0 576.0 0.0 485888.0 340310.0 1941504.0 60846.4 67968.0 64626.7 8576.0 7907.2 96 1.053 3 0.343 1.396
GC capacity情况 主要关注各区域最大最小空间
1 2 3 4 5 sh-4.2$ jstat -gccapacity 370 1000 3 NGCMN NGCMX NGC S0C S1C EC OGCMN OGCMX OGC OC MCMN MCMX MC CCSMN CCSMX CCSC YGC FGC 698880.0 10484736.0 850944.0 8192.0 13824.0 213504.0 1398272.0 20970496.0 1941504.0 1941504.0 0.0 1110016.0 68224.0 0.0 1048576.0 8576.0 228 3 698880.0 10484736.0 850944.0 8192.0 13824.0 213504.0 1398272.0 20970496.0 1941504.0 1941504.0 0.0 1110016.0 68224.0 0.0 1048576.0 8576.0 228 3 698880.0 10484736.0 850944.0 8192.0 13824.0 213504.0 1398272.0 20970496.0 1941504.0 1941504.0 0.0 1110016.0 68224.0 0.0 1048576.0 8576.0 228 3
GC cause 情况 主要关注导致GC的原因
1 2 3 4 5 sh-4.2$ jstat -gccause 370 1000 3 S0 S1 E O M CCS YGC YGCT FGC FGCT GCT LGCC GCC 93.81 0.00 73.52 4.29 95.02 92.27 240 2.204 3 0.343 2.546 Allocation Failure No GC 93.81 0.00 73.52 4.29 95.02 92.27 240 2.204 3 0.343 2.546 Allocation Failure No GC 93.81 0.00 73.53 4.29 95.02 92.27 240 2.204 3 0.343 2.546 Allocation Failure No GC
GC utils情况 主要关注内存占比
1 2 3 4 5 sh-4.2$ jstat -gcutil 370 1000 3 S0 S1 E O M CCS YGC YGCT FGC FGCT GCT 0.00 96.98 13.54 4.28 95.01 92.27 235 2.167 3 0.343 2.510 0.00 96.98 13.54 4.28 95.01 92.27 235 2.167 3 0.343 2.510 0.00 96.98 13.56 4.28 95.01 92.27 235 2.167 3 0.343 2.510
printcompilation情况 JIT的方法
1 2 3 4 5 sh-4.2$ jstat -printcompilation 370 1000 3 Compiled Size Type Method 13367 285 1 javax/management/ObjectName setCanonicalName 13367 285 1 javax/management/ObjectName setCanonicalName 13367 285 1 javax/management/ObjectName setCanonicalName
Jinfo jinfo能输出一个进程的基本信息，包括他的配置、用户、路径、命令行等等
1 2 3 4 5 6 7 8 9 10 11 12 13 sh-4.2$ jinfo 370 Attaching to process ID 370, please wait... Debugger attached successfully. Server compiler detected. JVM version is 25.252-b4 Java System Properties: java.runtime.name = OpenJDK Runtime Environment java.vm.version = 25.252-b4 java.protocol.handler.pkgs = org.springframework.boot.loader path.separator = : file.encoding.pkg = sun.io java.vm.name = OpenJDK 64-Bit Server VM
Jhat jhat是堆快照分析工具，用于分析堆的情况，首先要用jmap导出堆到文件dump.bin中，然后使用jhat分析,再访问7000端口即可
1 2 3 4 5 6 7 8 9 10 sh-4.2$ jhat dump.bin Reading from dump.bin... Dump file created Fri Sep 24 19:38:36 CST 2021 Snapshot read, resolving... Resolving 4748880 objects... Chasing references, expect 949 dots............. Eliminating duplicate references.............. Snapshot resolved. Started HTTP server on port 7000 Server is ready.
Javah 用于编写JNI方法
JavaP 字节码分析工具
Jshell Java交互式工具
1 2 3 4 5 6 7 8 9 10 11 12 13 sh-4.2$ jshell | 欢迎使用 JShell -- 版本 16.0.2 | 要大致了解该版本, 请键入: /help intro jshell> int a = 1 a ==> 1 jshell> int b = 1 b ==> 1 jshell> System.out.print(a+b) 2 jshell>
