JSTAT is a lightweight tool that comes with JDK. The JSTAT tool is particularly powerful, with many options. View the amount of each part in the heap, and the number of loading classes.

parameter explanation

• JSTAT -Class Pid Show the number of Class and the space occupied.

[root@S10 activity-assembly]# jstat -class 29202
Loaded  Bytes  Unloaded  Bytes     Time   
  5466 10500.1        0     0.0       6.51

######Explanation######Loaded loading number 
 The number of bytes occupied by Bytes loading class 
 The number of unloading classes unloaded 
 Bytes uninstalled byte number 
 The time spent on the time of time loading and uninstalling

• JSTAT -GC PID display the information of GC, check the number of GCs, time.

[[email protected] activity-assembly]# jstat -gc 29202
 S0C    S1C    S0U    S1U      EC       EU        OC         OU       PC     PU    YGC     YGCT    FGC    FGCT     GCT   
26176.0 26176.0 15152.1  0.0   209792.0 117634.8 1835008.0    6681.5   131072.0 31360.0      4    0.151   0      0.000    0.151###### Explanation ###### 
 The capacity (byte) of the first Survivor (surviving area) in the young generation of S0C 
 The capacity (byte) of the second Survivor (interest) of the second S1C in S1C 
 The first Survivor (surviving area) in the young generation of S0U is currently using space (byte) 
 The second Survivor (surviving area) in the young generation of S1U currently uses space (byte) 
 EC's young generation Eden capacity (byte) 
 EU young generation Eden currently uses space (byte) 
 OCOldgeneration capacity (byte) 
 OUOldgenerations currently used space (byte) 
 PC Perm capacity (byte) 
 PU PERM (Dowager) currently used space (byte) 
 YGC from the application to the number of GC times when the application starts to the sample 
 YGCT time from the application to the time of the young generation of GC used from the application to the sample (s) 
 FGC starts from the application to samplingoldgeneration (all GC) GC times 
 FGCT starts from the application to samplingoldgeneration (all GC) GC time (s) 
 The total time of GC used from the application to sampling from the application (s)

• jstat -GCUTIL PID statistics GC information.

[[email protected] activity-assembly]# jstat -gcutil 29202
  S0     S1     E      O      P     YGC     YGCT    FGC    FGCT     GCT   
 57.89   0.00  65.30   0.36  24.18      4    0.151     0    0.000    0.151###### Interpretation ###### 
 The first Survivor (surviving area) in the young generation has used the current percentage of the current capacity 
 The second Survivor (surviving area) in the young generation has accounted for the current percentage of the current capacityE15 15 15 15 15 has the current percentage of the current capacityOOLD's currently used percentage of the current capacity 
 P PERM's currently used current percentage percentage percentage