Common monitoring jvm commands
The command involved in this article is jps jstat jmap jstack jinfo
jps
Command format
jps [options] [hostid]
[] optional
options parameter list
- -l: output the full name of the main class or jar path
- -q: only LVMID(local virtual machine id) is output, that is, the unique id of the local virtual machine
- -m: output the parameters passed to main() when the JVM starts
- -v: the specified JVM parameters are displayed when the output JVM starts
Common jps / jps -l / jps -lmv
jinfo
This command is used to view and adjust the running parameters of the virtual machine in real time. The previous jps -v password can only view and display the specified parameters. If you want to view the values of the specified parameters that are not displayed, you need to use the jinfo password
Command format
jinfo [options] [args] LVMID
options parameter list
- -flag: outputs the value of the specified args parameter
- -flags: the args parameter is not required, and the values of all JVM parameters are output
- -sysprops: output system properties, equivalent to System.getProperties()
[root@VM-0-17-centos ~]# jinfo -flags 14878 JVM version is 25.281-b09 Non-default VM flags: -XX:CICompilerCount=3 -XX:InitialHeapSize=262144000 -XX:MaxHeapSize=4164943872 -XX:MaxNewSize=1388314624 -XX:MinHeapDeltaBytes=524288 -XX:NewSize=87031808 -XX:OldSize=175112192 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseParallelGC jinfo 14878 Output without any parameters jvm All parameters and attributes
Common jinfo /jinfo -flags / jinfo -sysprops
jstat
Command format
jstat [option] LVMID [interval] [count]
[] optional
[option] : Operating parameters,By command: jstat -options Get operation parameter list LVMID : Local virtual machine process ID [interval] : Time interval of continuous output [count] : Number of consecutive outputs
| Operating parameters | describe |
|---|---|
| class | Behavior statistics of class loader. Statistics on the behavior of the class loader. |
| compiler | Hotspot JIT compiler behavior statistics. Statistics of the behavior of the HotSpot Just-in-Time compiler. |
| gc | Behavior statistics of garbage collection heap. Statistics of the behavior of the garbage collected heap. |
| gccapacity | The capacity of each garbage collection generation (young,old,perm) and their corresponding spatial statistics. Statistics of the capacities of the generations and their corresponding spaces. |
| gcutil | Overview of garbage collection statistics. Summary of garbage collection statistics. |
| gccause | Overview of garbage collection statistics (the same as -gcutil), with reasons for the last two garbage collection events attached. Summary of garbage collection statistics (same as -gcutil), with the cause of the last and |
| gcnew | New generation behavior statistics. Statistics of the behavior of the new generation. |
| gcnewcapacity | Statistics of Cenozoic and its corresponding memory space. Statistics of the sizes of the new generations and its corresponding spaces. |
| gcold | Behavioral statistics of the elderly and immortals. Statistics of the behavior of the old and permanent generations. |
| gcoldcapacity | Behavioral statistics of the elderly. Statistics of the sizes of the old generation. |
| gcpermcapacity/gcmetacapacity | Immortality / meta spatial behavior statistics. Statistics of the sizes of the permanent generation. |
| printcompilation | Hotspot compilation method statistics. HotSpot compilation method statistics. |
Practical application analysis
class
Monitor class loading, unloading quantity, total space and time spent
[root@VM-0-17-centos ~]# jstat -class 14878 Loaded Bytes Unloaded Bytes Time 18014 32382.1 518 779.2 21.80 Loaded : load class Number of Bytes : class Byte size Unloaded : Not loaded class Number of Bytes : Not loaded class Byte size of Time : Loading time
compiler
Output the number of JIT compiled methods, time-consuming, etc
[root@VM-0-17-centos ~]# jstat -compiler 14878 Compiled Failed Invalid Time FailedType FailedMethod 22598 3 0 94.82 1 org/springframework/boot/loader/jar/Handler openConnection Compiled : Number of compilations Failed : Number of compilation failures Invalid : Invalid quantity Time : Compilation time FailedType : Failure type FailedMethod : The fully qualified name of the failed method
gc (*)
Garbage collection heap behavior statistics, common commands
[root@VM-0-17-centos ~]# jstat -gc 14878 S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT 2048.0 2048.0 0.0 1200.4 47616.0 41616.0 300544.0 125257.1 103680.0 96331.0 12800.0 11627.1 2183 16.327 5 0.995 17.322 C Namely Capacity Total capacity, U Namely Used Used capacity,Company: KB S0C : survivor0 Total capacity of area S1C : survivor1 Total capacity of area S0U : survivor0 Used capacity of zone S1C : survivor1 Used capacity of zone EC : Eden Total capacity of area EU : Eden Used capacity of zone OC : Old Total capacity of area OU : Old Used capacity of zone MC : Method area size MU : Method area usage size CCSC : Compressed class space size CCSU : Compressed class space usage size YGC : New generation garbage collection times YGCT : New generation garbage collection time FGC : Garbage collection times in old age FGCT : Old age garbage collection time GCT : Total waste collection time
gccapacity
The same as - gc, but it also outputs the maximum and minimum space used by each region of the Java heap
[root@VM-0-17-centos ~]# jstat -gccapacity 14878 NGCMN NGCMX NGC S0C S1C EC OGCMN OGCMX OGC OC MCMN MCMX MC CCSMN CCSMX CCSC YGC FGC 84992.0 1355776.0 51712.0 2048.0 2048.0 47616.0 171008.0 2711552.0 300544.0 300544.0 0.0 1140736.0 103680.0 0.0 1048576.0 12800.0 2184 5 NGCMN: Cenozoic minimum capacity NGCMX: Cenozoic maximum capacity NGC: Current Cenozoic capacity S0C: Size of the first surviving area S1C: The size of the second surviving area EC: The size of Eden Park OGCMN: Minimum capacity in old age OGCMX: Old age maximum capacity OGC: Current generation size OC:Current generation size MCMN:Minimum metadata capacity MCMX: Maximum metadata capacity MC: Current metadata space size CCSMN: Minimum compressed class space size CCSMX: Maximum compressed class space size CCSC: Current compressed class space size YGC: Young generation gc frequency FGC: Old age GC frequency
gcutil
Same as - gc, but the output is the percentage of used space in the total space
[root@VM-0-17-centos ~]# jstat -gcutil 14878 S0 S1 E O M CCS YGC YGCT FGC FGCT GCT 76.59 0.00 56.40 41.68 92.91 90.84 2184 16.332 5 0.995 17.327 S0: Current usage ratio of zone 1 S1: Current usage ratio of zone 2 E: Proportion of Eden Park O: Use proportion in old age M: Usage ratio of metadata area CCS: Compression usage ratio YGC: Garbage collection times of young generation FGC: Garbage collection times in old age FGCT: Waste collection in the old age takes time GCT: Total waste collection time
gcnew
New generation garbage collection statistics
[root@VM-0-17-centos ~]# jstat -gcnew 14878 S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT 2048.0 2048.0 0.0 1648.6 15 15 2048.0 47616.0 3043.1 2185 16.337 S0C: Size of the first surviving area S1C: The size of the second surviving area S0U: Use size of the first surviving area S1U: Use size of the second surviving area TT:The number of times the object survived in the Cenozoic MTT:The maximum number of times the object survived in the Cenozoic DSS:Expected survival area size EC: The size of Eden Park EU: Use size of Eden Park YGC: Garbage collection times of young generation YGCT: Waste collection time of young generation
gcnewcapacity
New generation memory space statistics
[root@VM-0-17-centos ~]# jstat -gcnewcapacity 14878 NGCMN NGCMX NGC S0CMX S0C S1CMX S1C ECMX EC YGC FGC 84992.0 1355776.0 51712.0 451584.0 2048.0 451584.0 2048.0 1354752.0 47616.0 2185 5 NGCMN: Cenozoic minimum capacity NGCMX: Cenozoic maximum capacity NGC: Current Cenozoic capacity S0CMX: Maximum 1 zone size S0C: Current 1 area size S1CMX: Maximum 2 zone size S1C: Current 2 area size ECMX: Maximum Eden Park size EC: Current Eden Park size YGC: Garbage collection times of young generation FGC: Recovery times of old generation
gcold
Old age garbage collection statistics
[root@VM-0-17-centos ~]# jstat -gcold 14878 MC MU CCSC CCSU OC OU YGC FGC FGCT GCT 103680.0 96331.0 12800.0 11627.1 300544.0 125257.1 2185 5 0.995 17.332 MC: Current metadata space size MC: Used metadata space size CCSC: Current compressed class space size CCSC: Compressed class space size used OC: Total space for the elderly generation OU: Space used by older generation YGC: Garbage collection times of young generation FGC: Garbage collection times in old age FGCT: Waste collection in the old age takes time GCT: Total waste collection time
gcoldcapacity
Old memory space statistics
[root@VM-0-17-centos ~]# jstat -gcoldcapacity 14878 OGCMN OGCMX OGC OC YGC FGC FGCT GCT 171008.0 2711552.0 300544.0 300544.0 2185 5 0.995 17.332 OGCMN: Minimum capacity in old age OGCMX: Old age maximum capacity OGC: Current generation size OC: Old age size YGC: Garbage collection times of young generation FGC: Garbage collection times in old age FGCT: Waste collection in the old age takes time GCT: Total waste collection time
gcpermcapacity/gcmetacapacity
Meta space / immortality space statistics jdk1.8 and later unified into meta space
[root@VM-0-17-centos ~]# jstat -gcmetacapacity 14878 MCMN MCMX MC CCSMN CCSMX CCSC YGC FGC FGCT GCT 0.0 1140736.0 103680.0 0.0 1048576.0 12800.0 2186 5 0.995 17.337 MCMN:Minimum metadata capacity MCMX: Maximum metadata capacity MC: Current metadata space size CCSMN: Minimum compressed class space size CCSMX: Maximum compressed class space size CCSC: Current compressed class space size
printcompilation
Statistics of hotspot compilation methods
[root@VM-0-17-centos ~]# jstat -printcompilation 14878 Compiled Size Type Method 22598 5 1 java/util/ResourceBundle$CacheKey getCause Compiled: Number of compilation tasks executed Size: The number of bytes of the method bytecode Type: Compile type Method: Compile the class name and method name of the method. Class name usage"/" replace "." As space separator. The method name is the method name of the given class. The format is consistent with HotSpot - XX:+PrintComplation option
jmap
It can generate dump files of java programs, view statistics of object samples in the heap, view ClassLoader information, and finalize queues.
usage
[root@VM-0-17-centos ~]# jmap --help
Usage:
jmap [option] <pid>
(to connect to running process)
jmap [option] <executable <core>
(to connect to a core file)
jmap [option] [server_id@]<remote server IP or hostname>
(to connect to remote debug server)
where <option> is one of:
<none> to print same info as Solaris pmap
-heap to print java heap summary
-histo[:live] to print histogram of java object heap; if the "live"
suboption is specified, only count live objects
-clstats to print class loader statistics
-finalizerinfo to print information on objects awaiting finalization
-dump:<dump-options> to dump java heap in hprof binary format
dump-options:
live dump only live objects; if not specified,
all objects in the heap are dumped.
format=b binary format
file=<file> dump heap to <file>
Example: jmap -dump:live,format=b,file=heap.bin <pid>
-F force. Use with -dump:<dump-options> <pid> or -histo
to force a heap dump or histogram when <pid> does not
respond. The "live" suboption is not supported
in this mode.
-h | -help to print this help message
-J<flag> to pass <flag> directly to the runtime system
explain:
empty : View the memory image information of the process,similar Solaris pmap command
clstats: Print class loader information
dump : Generate heap dump snapshot
finalizerinfo : Show in F-Queue Queue waiting Finalizer Thread execution finalizer Object of method
heap : display Java Heap details
histo : Displays statistics for objects in the heap,If you bring it:live modification(jmap -histo:live),Only the currently surviving object information is displayed
permstat : to print permanent generation statistics
F : When-dump Force generation when there is no response dump snapshot
histro
Print the object statistics of the heap, including the number of objects, memory size, etc. (if you bring live, only live objects will be counted)
[root@VM-0-17-centos ~]# jmap -histo:live 14878 | more num #instances #bytes class name ---------------------------------------------- 1: 195366 20329280 [C 2: 194829 4675896 java.lang.String 3: 17718 3790208 [I 4: 39602 3484976 java.lang.reflect.Method 5: 86797 3471880 java.util.LinkedHashMap$Entry 6: 94630 3028160 java.util.concurrent.ConcurrentHashMap$Node 7: 51774 2971952 [Ljava.lang.Object; 8: 75934 2429888 java.util.HashMap$Node 9: 27548 2334504 [Ljava.util.HashMap$Node; 10: 9878 2234184 [B 11: 18447 2038720 java.lang.Class object type B byte C char D double F float I int J long Z boolean [ Array, such as[I express int[] [L+Class name other objects
permstat/clstats
Used to print classloader data & print intelligent statistics of classloader in the persistent storage area (meta space) of Java heap memory. For each class loader, its name, activity, address, parent class loader, and the number and size of classes it loads are printed. In addition, the number and size of strings contained are also printed.
[root@VM-0-17-centos ~]# jmap -clstats 14878 Attaching to process ID 14878, please wait... Debugger attached successfully. Server compiler detected. JVM version is 25.281-b09 finding class loader instances ..done. computing per loader stat ..done. please wait.. computing liveness.liveness analysis may be inaccurate ... class_loader classes bytes parent_loader alive? type <bootstrap> 3382 5936799 null live <internal> 0x00000006cbcb5bc8 1 1474 0x00000006c7d03660 dead sun/reflect/DelegatingClassLoader@0x00000007c000a0a0 0x00000006caad82a8 1 880 0x00000006c7d03660 dead sun/reflect/DelegatingClassLoader@0x00000007c000a0a0 0x00000006cbfeabf8 1 880 0x00000006c7d03660 dead sun/reflect/DelegatingClassLoader@0x00000007c000a0a0 0x00000006cbe883e0 1 880 0x00000006c7d03660 dead sun/reflect/DelegatingClassLoader@0x00000007c000a0a0 0x00000006cbc2abc8 1 880 0x00000006c7d03660 dead sun/reflect/DelegatingClassLoader@0x00000007c000a0a0 0x00000006cbeaebe0 1 880 0x00000006c7d03660 dead sun/reflect/DelegatingClassLoader@0x00000007c000a0a0 0x00000006c8bcd0b0 1 880 0x00000006c7d03660 dead sun/reflect/DelegatingClassLoader@0x00000007c000a0a0
F
Force mode. If the specified pid does not respond, use the jmap -dump or jmap -histo options. The live sub option is not supported in this mode.
finalizerinfo
Print information about objects waiting to be recycled
[root@VM-0-17-centos ~]# jmap -finalizerinfo 14878 Attaching to process ID 14878, please wait... Debugger attached successfully. Server compiler detected. JVM version is 25.281-b09 Number of objects pending for finalization: 0 You can see the current F-QUEUE There is no waiting in queue Finalizer Thread execution finalizer Method.
heap(*)
Print the summary information of heap, the algorithm used by GC, the configuration of heap and the usage of wise heap, which can be used to judge the current memory usage and garbage collection
[root@VM-0-17-centos ~]# jmap -heap 14878 Attaching to process ID 14878, please wait... Debugger attached successfully. Server compiler detected. JVM version is 25.281-b09 using thread-local object allocation. Parallel GC with 4 thread(s) # #gc type Heap Configuration: MinHeapFreeRatio = 0 # The minimum percentage of free heap space. The calculation formula is: HeapFreeRatio =(CurrentFreeHeapSize/CurrentTotalHeapSize) * 100. The range of values is 0 to 100, and the default value is 40. If heapfreeratio < minheapfreeratio, heap expansion is required. The expansion time should be after each garbage collection. MaxHeapFreeRatio = 100 # The maximum percentage of free heap space. The calculation formula is HeapFreeRatio =(CurrentFreeHeapSize/CurrentTotalHeapSize) * 100. The range of values is 0 to 100, and the default value is 70. If heapfreeratio > maxheapfreeratio, it is necessary to shrink the heap. The shrinking time should be after each garbage collection. MaxHeapSize = 4164943872 (3972.0MB) # Maximum heap space size NewSize = 87031808 (83.0MB) # Cenozoic size MaxNewSize = 1388314624 (1324.0MB) # Maximum Cenozoic size OldSize = 175112192 (167.0MB) # Old age size NewRatio = 2 # Proportion of old age: newratio = 2 = > old age: Cenozoic = 2:1 / newratio = 4 > old age: Cenozoic = 4:1 SurvivorRatio = 8 # Proportion of eden area in Cenozoic: default eden: S1: S0 = 8:1:1 survivorratio = 6 = > eden: S1: S0 = 6:1:1 MetaspaceSize = 21807104 (20.796875MB) # Meta space size CompressedClassSpaceSize = 1073741824 (1024.0MB) # The maximum allowable memory of Compressed Class Space in Metaspace is 1g by default. This part will apply for 1g virtual address mapping from the operating system when the JVM is started, but it does not really use 1G memory of the operating system. MaxMetaspaceSize = 17592186044415 MB # The maximum allowable memory of the total space of the Metaspace is unlimited by default G1HeapRegionSize = 0 (0.0MB) # G1 the size of the area in the garbage collector. The value is a power of 2, ranging from 1 MB to 32 MB; If the G1 collector is used, the java heap heap is divided into 2048 copies (java hopes to divide into 2048 copies, not only 2048 copies), and the size of each is g1heapregionsize (when not set, java will calculate automatically) Heap Usage: PS Young Generation Eden Space: capacity = 47185920 (45.0MB) used = 16805224 (16.026710510253906MB) free = 30380696 (28.973289489746094MB) 35.61491224500868% used From Space: capacity = 2097152 (2.0MB) used = 1245632 (1.18792724609375MB) free = 851520 (0.81207275390625MB) 59.3963623046875% used To Space: capacity = 2621440 (2.5MB) used = 0 (0.0MB) free = 2621440 (2.5MB) 0.0% used PS Old Generation capacity = 234881024 (224.0MB) used = 74456592 (71.00733947753906MB) free = 160424432 (152.99266052246094MB) 31.699705123901367% used 38016 interned Strings occupying 3954528 bytes.
dump
Generate heap dump snapshot
Command format: - dump:live,format=b,file= LVMID
Output dump to a file, format specifies the output format, live indicates that it is a living object, and file specifies the file name
jmap -dump:live,format=b,file=dump.hprof 14878 xxx.hprof Format files can be used jdk Own tools jvisualvm.exe see,have access to jhat Command view,have access to eclipse of mat Tool View,You can also specify other file formats.
jstack
jstack is used to generate a thread snapshot of the java virtual machine at the current time.
Thread snapshot is a collection of method stacks being executed by each thread in the current java virtual machine. The main purpose of generating thread snapshot is to locate the causes of long-time pause of threads, such as deadlock between threads, dead loop, long wait caused by requesting external resources, etc.
When a thread pauses, you can view the call stack of each thread through jstack to know what the unresponsive thread is doing in the background or waiting for resources.
If a java program crashes and generates a core file, the jstack tool can be used to obtain the information of the java stack and native stack of the core file, so that you can easily know how the Java program crashes and where the problem occurs in the program.
In addition, the jstack tool can also be attached to the running java program to see the information of the java stack and native stack of the running java program at that time. Jstack is very useful if the running java program presents a hung state.
Usage: jstack [option] LVMID
[root@VM-0-17-centos ~]# jstack -help
Usage:
jstack [-l] <pid>
(to connect to running process)
jstack -F [-m] [-l] <pid>
(to connect to a hung process)
jstack [-m] [-l] <executable> <core>
(to connect to a core file)
jstack [-m] [-l] [server_id@]<remote server IP or hostname>
(to connect to a remote debug server)
Options:
-F to force a thread dump. Use when jstack <pid> does not respond (process is hung)
-m to print both java and native frames (mixed mode)
-l long listing. Prints additional information about locks
-h or -help to print this help message
-F : Force the output thread stack when the normal output request is not responded
-l : Keep listening,In addition to the stack, additional information about the lock is displayed
-m : If you call a local method, you can display C/C++Stack of
[root@VM-0-17-centos ~]# jstack 14878 | more