Turn: Jstat command

Jstat is a lightweight gadget that comes with the JDK. The full name "Java Virtual machine Statistics monitoring Tool", which is located in the Java Bin directory, mainly uses the JVM built-in instructions for Java application resources and performance of real-time command line monitoring, including the heap Monitoring of size and garbage collection status. Visible, Jstat is a lightweight, JVM-specific tool that works well.

The Jstat tool is particularly powerful and has a number of options to view in detail the usage of each part of the heap, as well as the number of loaded classes. When used, add the process ID of the viewing process and the selected parameters. The reference format is as follows:

Jstat-options

You can list the options supported by the current JVM version, which are common

• L Class (class loader)
• l Compiler (JIT)
• L GC (GC heap status)
• L gccapacity (each district size)
• L Gccause (last GC statistics and causes)
• L gcnew (New zone statistics)
• L gcnewcapacity (new zone size)
• L Gcold (Old Quarter statistics)
• L gcoldcapacity (old quarter size)
• L gcpermcapacity (Permanent zone size)
• L Gcutil (GC statistics Rollup)
• L Printcompilation (Hotspot compilation statistics)

1, jstat–class<pid>: Display the number of loading class, and the space occupied information.

Show Column names	Specific description
Loaded	The number of classes loaded
Bytes	The number of bytes occupied by the load class
Unloaded	Unload the number of classes
Bytes	Number of bytes to unload class
Time	Time taken to load and unload classes

2, Jstat-compiler <pid> shows the number of VMS in real-time compilation and other information.

Show Column names	Specific description
Compiled	Number of compile task executions
Failed	Number of failed compile task executions
Invalid	Compile task execution Failure quantity
Time	Compile task consumption time
Failedtype	The type of the last compilation failure task
Failedmethod	The class and method where the last compilation failure task is located

3, JSTAT-GC <pid>: The GC information can be displayed, the number of times the GC is viewed, and the time.

Show Column names	Specific description
s0c	Capacity of the first Survivor (Survivor area) in the Young Generation (bytes)
S1c	Capacity of the second survivor (Survivor area) in the younger generation (bytes)
s0u	The first survivor (Survivor area) of the young generation has currently used space (bytes)
s1u	The second survivor (Survivor area) of the young generation has currently used space (bytes)
EC	The capacity of Eden (Eden) in the Young Generation (bytes)
EU	The young generation of Eden (Eden) has currently used space (bytes)
Oc	Capacity in old generation (bytes)
OU	Old generation currently used space (bytes)
Pc	Perm (persistent generation) capacity (bytes)
Pu	Perm (persistent generation) currently used space (bytes)
Ygc	Number of GC times in young generations from application startup to sampling
Ygct	Time taken by the young generation GC from application startup to sampling (s)
FGC	Old (full GC) GC times from application startup to sampling
Fgct	Time (s) used by the old (full GC) GC from application startup to sampling
GCT	Total time (s) used by GC from application startup to sampling

4,jstat-gccapacity <pid>: can display the use and occupancy of three-generation (Young,old,perm) objects in VM memory

Show Column names	Specific description
Ngcmn	Initial (minimum) size in Young generation (bytes)
Ngcmx	Max capacity of young generation (bytes)
Ngc	Current capacity in young generation (bytes)
s0c	Capacity of the first Survivor (Survivor area) in the Young Generation (bytes)
S1c	Capacity of the second survivor (Survivor area) in the younger generation (bytes)
EC	The capacity of Eden (Eden) in the Young Generation (bytes)
Ogcmn	Initial (minimum) size in old generation (bytes)
Ogcmx	Maximum capacity in old generation (bytes)
OGC	The current newly generated capacity of the old generation (bytes)
Oc	Capacity in old generation (bytes)
Pgcmn	The size (in bytes) of the initialization (minimum) in perm generation
Pgcmx	Maximum capacity of the perm generation (bytes)
Pgc	The current newly generated capacity of the perm generation (bytes)
Pc	Perm (persistent generation) capacity (bytes)
Ygc	Number of GC times in young generations from application startup to sampling
FGC	Old (full GC) GC times from application startup to sampling

5, Jstat-gcutil <pid>: Statistics GC Information

Show Column names	Specific description
S0	The first survivor (Survivor area) in the younger generation has been used as a percentage of current capacity
S1	The second survivor (Survivor area) of the young generation has been used as a percentage of current capacity
E	Eden (Eden) in the young generation has been used as a percentage of current capacity
O	Percentage of current capacity used by old generation
P	Percentage of current capacity used by perm generation
Ygc	Number of GC times in young generations from application startup to sampling
Ygct	Time taken by the young generation GC from application startup to sampling (s)
FGC	Old (full GC) GC times from application startup to sampling
Fgct	Time (s) used by the old (full GC) GC from application startup to sampling
GCT	Total time (s) used by GC from application startup to sampling

6, Jstat-gcnew <pid>: Information of the young generation object.

Show Column names	Specific description
s0c	Capacity of the first Survivor (Survivor area) in the Young Generation (bytes)
S1c	Capacity of the second survivor (Survivor area) in the younger generation (bytes)
s0u	The first survivor (Survivor area) of the young generation has currently used space (bytes)
s1u	The second survivor (Survivor area) of the young generation has currently used space (bytes)
Tt	Number of holding limits
Mtt	Maximum number of hold limits
EC	The capacity of Eden (Eden) in the Young Generation (bytes)
EU	The young generation of Eden (Eden) has currently used space (bytes)
Ygc	Number of GC times in young generations from application startup to sampling
Ygct	Time taken by the young generation GC from application startup to sampling (s)

7, Jstat-gcnewcapacity<pid>: Information of young generation objects and their occupancy.

Show Column names	Specific description
Ngcmn	Initial (minimum) size in Young generation (bytes)
Ngcmx	Max capacity of young generation (bytes)
Ngc	Current capacity in young generation (bytes)
S0cmx	Maximum capacity of the first Survivor (Survivor area) in the Young Generation (bytes)
s0c	Capacity of the first Survivor (Survivor area) in the Young Generation (bytes)
S1cmx	Maximum capacity of the second survivor (Survivor area) in the younger generation (bytes)
S1c	Capacity of the second survivor (Survivor area) in the younger generation (bytes)
Ecmx	Maximum capacity of Eden (Eden) in the Young Generation (bytes)
EC	The capacity of Eden (Eden) in the Young Generation (bytes)
Ygc	Number of GC times in young generations from application startup to sampling
FGC	Old (full GC) GC times from application startup to sampling

8, Jstat-gcold <pid>:old The information of the object.

Show Column names	Specific description
Pc	Perm (persistent generation) capacity (bytes)
Pu	Perm (persistent generation) currently used space (bytes)
Oc	Capacity in old generation (bytes)
OU	Old generation currently used space (bytes)
Ygc	Number of GC times in young generations from application startup to sampling
FGC	Old (full GC) GC times from application startup to sampling
Fgct	Time (s) used by the old (full GC) GC from application startup to sampling
GCT	Total time (s) used by GC from application startup to sampling

9, stat-gcoldcapacity <pid>: The information of the old generation object and its consumption.

Show Column names	Specific description
Ogcmn	Initial (minimum) size in old generation (bytes)
Ogcmx	Maximum capacity in old generation (bytes)
OGC	The current newly generated capacity of the old generation (bytes)
Oc	Capacity in old generation (bytes)
Ygc	Number of GC times in young generations from application startup to sampling
FGC	Old (full GC) GC times from application startup to sampling
Fgct	Time (s) used by the old (full GC) GC from application startup to sampling
GCT	Total time (s) used by GC from application startup to sampling

10, Jstat-gcpermcapacity<pid>: Information of Perm objects and their occupancy.

Show Column names	Specific description
Pgcmn	The size (in bytes) of the initialization (minimum) in perm generation
Pgcmx	Maximum capacity of the perm generation (bytes)
Pgc	The current newly generated capacity of the perm generation (bytes)
Pc	Perm (persistent generation) capacity (bytes)
Ygc	Number of GC times in young generations from application startup to sampling
FGC	Old (full GC) GC times from application startup to sampling
Fgct	Time (s) used by the old (full GC) GC from application startup to sampling
GCT	Total time (s) used by GC from application startup to sampling

11, Jstat-printcompilation <pid>: Current VM execution information.

Show Column names	Specific description
Compiled	Number of compilation tasks
Size	Size of bytecode generated by method
Type	Compilation type
Method	The class name and method name are used to identify the compiled method. The class name is used/as a namespace delimiter. The method name is a method in a given class. The above format is set by the-xx:+printcomplation option

Turn: Jstat command