What's the meaning of "CGC" and "CGCT" in JDK11 "jstat -gc <PID>"?

Question

There are two items called CGC and CGCT. I cannot found the documention and man page describing their meaning.

# jstat -gc 139934
 S0C    S1C    S0U    S1U      EC       EU        OC         OU       MC     MU    CCSC   CCSU   YGC     YGCT    FGC    FGCT    CGC    CGCT     GCT   
 0.0   15360.0  0.0   15360.0 113664.0  9216.0   88064.0    23552.0   82304.0 80084.2 10112.0 9360.4     10    0.157   0      0.000   6      0.018    0.175

# java -version 
openjdk version "11.0.2" 2019-01-15 LTS
OpenJDK Runtime Environment Corretto-11.0.2.9.3 (build 11.0.2+9-LTS)
OpenJDK 64-Bit Server VM Corretto-11.0.2.9.3 (build 11.0.2+9-LTS, mixed mode

I used the default jvm arguments.

#jhsdb jmap --heap --pid 139934 | grep GC
Garbage-First (G1) GC with 13 thread(s)

Estelleesten

Answer 1

As far as I understand from this link, the first C in CGC and CGCT stands for "concurrent", so based on the description from the docs for GC and GCT:

GCT: Total garbage collection time.

I would say CGTC is "Concurrent Total Garbage Collection" and CGC is "Concurrent Garbage Collection".

Meld

Answer 2

According to this, CGC and CGCT are indications of ZGC, a concurrent garbage collector. So the two terms can be explained as:

CGC: Concurrent GC Count
CGCT: Concurrent GC Collection Time

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