011-JDK Visual monitoring Tool-jstat

I. Overview

　　Jstat is a lightweight gadget that comes with the JDK. Full name "Java Virtual machine Statistics monitoring Tool", which is located in the Java Bin directory, mainly using the JVM built-in instructions to The resources and performance of Java applications are monitored in real time on the command line, including the Heap size and garbage collection status. Visible,Jstat is a lightweight, JVM-specific tool that works well. The percentage change in the graph is less noticeable due to the large JVM memory settings

A very strong monitoring VM memory tool. can be used to monitor the size of various heap and non-heap sizes and their memory usage within VM memory.

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.

Execution:CD $JAVA _home/bin in the execution of Jstat, note that after jstat must be followed by parameters.

1.1. Grammatical structure:

Usage:jstat-help|-options

Jstat-<option> [-t] [-h<lines>] <vmid> [<interval> [<count>]

Parameter explanation:

options-option, we generally use-gcutil to view GC conditions

The VMID-VM process number, which is the currently running Java process number

interval– interval time, in seconds or milliseconds

count-printing times, if the default is printed countless times

1.2. Specific Use

where PID gets

Window under: JPS

Linux:ps-ef | grep java

1. JSTAT-GC PID

You can display GC information, the number of times the GC is viewed, and the time.

The last five items were 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 use and occupancy of three generation (Young,old,perm) objects in VM memory,

For example: PGCMN shows the minimum perm memory usage, PGCMX shows the maximum memory usage of perm,

The PGC is the current newly generated perm memory footprint, and the PC is but the pre-perm memory footprint.

The other can be based on this analogy, OC is the old inside the pure consumption.

3.jstat-gcutil PID

Statistical GC information Statistics.

4.jstat-gcnew PID

Information about the young generation object.

5.jstat-gcnewcapacity PID

The information of the young generation object and its consumption.

6.jstat-gcold PID

The information for the old generation object.

7.stat-gcoldcapacity PID

The information and consumption of the old generation object.

8.jstat-gcpermcapacity PID

The information of the Perm object and its consumption.

9.jstat-class PID

Displays information such as the number of loaded classes, and the amount of space occupied.
10.jstat-compiler PID

Displays information such as the number of real-time VMS compiled.

11.jstat-printcompilation PID

1.3, the Chinese interpretation of the term:

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: Eden (Eden) in the young generation has currently used space (bytes)
Capacity of the Oc:old generation (bytes)
Ou:old 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: The time taken by the GC in the young generation from application startup to sampling (s)
FGC: Old (full GC) GC count from application boot to sampling
FGCT: Time taken from an old (full GC) GC when the application boots to sampling (s)
GCT: GC Total time from Application boot to sample (s)

NGCMN: initial (minimum) size in Young generation (bytes)

NGCMX: Max capacity of young generation (bytes)

NGC: Current capacity in young generation (bytes)

The size (in bytes) of the initialization (minimum) in ogcmn:old generation

Maximum capacity of the Ogcmx:old generation (bytes)

The current newly generated capacity of the Ogc:old generation (bytes)

The size (in bytes) of the initialization (minimum) in pgcmn:perm generation

Maximum capacity of the Pgcmx:perm generation (bytes)

The current newly generated capacity of the Pgc:perm generation (bytes)

S0: The first survivor (Survivor area) of the young generation has been used as a percentage of current capacity

S1: The second survivor (Survivor area) in the younger 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

Percentage of current capacity used by O:old generation

Percentage of current capacity used by P:perm generation

S0CMX: Maximum Capacity (bytes) of the first Survivor (Survivor area) in the young generation

S1CMX: Maximum capacity of the second survivor (Survivor area) in the younger generation (bytes)

ECMX: Maximum capacity of Eden (Eden) in the Young Generation (bytes)

DSS: Capacity (bytes) currently required for Survivor (surviving area) (Eden area Full)

TT: Limited number of holds

MTT: Maximum number of hold limit

011-JDK Visual monitoring Tool-jstat