About JVM to view GC consumption

ps (Java Virtual Machine Process Status Tool) is a command provided by JDK to display the pid of all current java processes. It is simple and practical, and is very suitable for simply viewing some simple situations of the current java process on the linux/unix platform.

jps is stored in JAVA_HOME/bin/jps. For convenience, please add JAVA_HOME/bin/ to Path.


jstat
       1. jstat -gc pid
            can display gc information, check the number and time of gc.
            The last five items are the number of young gc, the time of young gc, the number of full gc, the time of full gc, and the total time of gc.
      2. jstat -gccapacity pid
            can display the usage and size of three generations (young, old, perm) objects in VM memory, for
            example: PGCMN displays the minimum perm memory usage, PGCMX displays the perm maximum memory usage ,
            PGC is the current newly generated perm memory footprint, PC is the previous perm memory footprint.
            Others can be analogized according to this, OC is the pure occupancy in old.
     3.jstat -gcutil pid
            statistics gc information statistics.
     4.jstat -gcnew pid
           young generation object information.
     5.jstat -gcnewcapacity pid
           young generation object information and its occupancy.
     6.jstat -gcold pid
          old generation object information.
     7.stat -gcoldcapacity pid
          old generation object information and its occupancy.
     8.jstat -gcpermcapacity pid
          perm object information and its occupancy.
     9.jstat -class pid
          displays information such as the number of loaded classes and the space they occupy.
     10.jstat -compiler pid
          displays information such as the number of VM real-time compilations.
     11.stat -printcompilation pid
          information about the current VM execution.
        Chinese explanations of some terms:
         S0C: The capacity of the first survivor (survivor area) in the young generation (bytes)
         S1C: The capacity of the second survivor (survivor area) in the young generation (bytes)
         S0U: The first survivor in the young generation A survivor (survivor area) currently used space (bytes)
         S1U: The second survivor (survivor area) in the young generation currently uses space (bytes)
         EC: The capacity of Eden (Garden of Eden) in the
         young generation (bytes) EU: The space currently used by Eden (Garden of Eden) in the young generation (bytes)
         OC: The capacity of the Old generation (bytes)
         OU: The currently used space of the Old generation (bytes)
         PC: Perm (persistent generation) capacity (bytes)
         PU: Perm (persistent generation) currently used space (bytes)
         YGC: The number of gcs in the young generation from application startup to sampling
         YGCT: From the application The time spent by gc in the young generation from the start of the program to the sampling time (s)
         FGC: from the start of the application to the time of sampling the old generation (full gc) gc times
         FGCT: the time from the application startup to the sampling time of the old generation (full gc) gc ( s)
         GCT: Total time from application startup to sampling time (s)
         NGCMN: Initialization (minimum) size (bytes)
         in young generation NGCMX: Young generation (young) maximum capacity (bytes) )
         NGC: The current capacity (bytes) in the young generation (byte)
         OGCMN: The initialized (minimum) size (bytes)
         in the old generation OGCMX: The maximum capacity of the old generation (bytes)
         OGC: The current new generation of the old generation Capacity (bytes)
         PGCMN: Initialized (minimum) size (bytes)
         of the perm generation PGCMX: Maximum capacity of the perm generation (bytes)  
         PGC: The current newly generated capacity of the perm generation (bytes)
         S0: The first survivor (survivor) in the young generation S1: The percentage of the current capacity used by the
         second survivor (survivor) in the
         young generation E: The percentage of the current capacity used by Eden (Eden) in the young generation
         O: The old generation has been used Used percentage of current capacity
         P: Perm generation used percentage of current capacity
         S0CMX: Maximum capacity (bytes) of the first survivor (survivor area) in the
         young generation S1CMX: The second survivor (survivor area) in the young generation Maximum capacity (bytes)
         ECMX: Maximum capacity (bytes) of Eden (Garden of Eden) in the young generation
         DSS: Capacity (bytes) of the survivor (survivor area) currently required (Eden area is full)
         TT: Holding times limit
         MTT: Maximum number of holdings