1, the class loading information
wherein jstat -class 4431 1000 10 1000 denotes performed once every one second, 10 denotes an output 10
-Class outputted Loaded result indicates the number of classes loaded, loaded Bytes represents the number of K, Unloaded represents the number of unloaded classes, unloaded third field indicates the number of Bytes K, Time spent in the class represents the loading and unloading time
Specific Command Reference https://docs.oracle.com/javase/8/docs/technotes/tools/unix/index.html
2, garbage collection information
Parameters: -gc, -gcutil, -gccause, -gcnew, -gcold
Example commands: jstat -gc 4431 1000 3
Meaning -gc output under JDK1.8 case
S0C, S1C, S0U, S1U: S0 and S1 and the total amount of
EC, EU: the total amount of the Eden District
OC, OU: the total amount of the Old District
MC, MU: Metaspace total area of usage
CCSC, CCSU: the compression and the total amount of space
YGC, YGCT: the number and time of YoungGC
FGC, FGCT: FullGC the number and time
GCT: The total GC time
Command specific use with the above URL
JVM memory structure
JVM heap memory is divided into areas and non-heap area, stack area is divided into Young and Old District, Yong divided into Survivor and Eden, Survivor composed by the S0 and S1, S0 and S1 as large, at the same point in time only one is enabled, the other is empty. JDK1.8 non-heap area Metaspace of CCS, when we opened a short pointer, will exist CCS; when CodeCache JIT code information is stored, that is, the Java code into Native code is stored in the CodeCache
3, JIT compiler
Parameters: -compiler, -printcompilation
Order Example: jstat -compiler 4431
-compiler输出结果中Compiled表示完成了多少个编译的任务 ，Failed表示失败的，Invalid表示无效的
命令具体使用同上述网址
