9.7.1 Overview of the pre-statistical GC selection functionality
You can execute the class-wise statistical functionality to output the class-wise statistical information to the extended thread dump. In the pre-statistical GC selection functionality, you can select the processing that is to be executed before the class-wise statistical information is output. By selecting this processing that is to be executed, you can acquire the various changes in the appearance of the Java object in the class-wise statistical information, depending on the purpose of investigation.
When using the pre-statistical GC selection functionality, specify the processing to be executed by an argument of the jheapprof command. The following table lists the process and the arguments of the jheapprof commands that can be implemented before executing the class-wise statistical functionality.
|
Type of process |
Process contents |
Argument of the jheapprof command |
|---|---|---|
|
Execution of a Full GC |
Collects the used object for an entire JavaVM specific area even including Tenured area. |
-fullgc |
|
Execution of a copy GC |
Collects the used object only for the Eden area and for the Survivor area |
-copygc |
|
No execution of any GC |
Does not collect the used object though available. |
-nogc |
Note that if you execute the class-wise statistical functionality when specifying -XX:+HitachiVerboseGC and -XX:+HitachiVerboseGCPrintCause in the JavaVM start option, the following information is output to extended verbosegc information:
-
Type of GC
-
Cause for GC occurrence in the extended thread dump
The above information differs with the information output by an argument specified in the jheapprof command. The following table lists the relation between the arguments of the jheapprof command and the output information.
|
Argument of the jheapprof command |
Type of GC |
Cause for GC occurrence |
|---|---|---|
|
-fullgc |
Full GC |
JHeapProf Command |
|
-copygc |
GC |
JHeapProf Command |