RFR (M) JDK-6479360 - detailed dumping of class size statistics

[Ioi Lam]

Please review:
     http://cr.openjdk.java.net/~acorn/class_stats_010/

Bug: RFE: PrintClassHistogram improvements
     https://jbs.oracle.com/bugs/browse/JDK-6479360

Sponsor: Karen Kinnear

Summary:

A new diagnostic command "jcmd GC.class_stats" is added. The user
can invoke this command to connect to a live JVM and dump a detailed
report of size statistics of all loaded classes (including array
classes and anonymous classes).

     ==========SYNOPSIS===================================
     $ jcmd $PID help GC.class_stats
     Provide statistics about Java class meta data.
     Impact: High: Depends on Java heap size and content.

     Syntax : GC.class_stats [options] [<columns>]

     Arguments:
	columns : [optional] Comma-separated list of all the columns to
                   show. If not specified, the following columns are shown:
                   InstBytes,KlassBytes,CpAll,annotations,MethodCount,Bytecodes,
                   MethodAll,ROAll,RWAll,Total (STRING, no default value)

     Options: (options must be specified using the <key> or <key>=<value> syntax)
	-all : [optional] Show all columns (BOOLEAN, false)
	-csv : [optional] Print in CSV (comma-separated values) format for
                 spreadsheets (BOOLEAN, false)
	-help : [optional] Show meaning of all the columns (BOOLEAN, false)
     ======================================================

By default, the output is human-readable tabulated text format. The
user can also select CSV format (comma-separated values) to be
used with spreadsheets.

A large number of columns are available. By default, a few "summary
columns" (e.g., size of Klass objects, total read-only data, etc)
are printed. The user can also manually select the columns.

Please see the attachments in the bug for sample output, as well as
a listing of all the columns and their meanings:

https://jbs.oracle.com/bugs/browse/JDK-6479360?focusedCommentId=13290360&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13290360



Impact:

If this diagnostic command is not used, there should be no
impact to the JVM's execution, except for

    + libjvm.so footprint increase (about 10KB larger on Linux/x64)
    + one additional virtual method in Klass.

This feature is excluded when INCLUDE_SERVICES=0 (e.g.,
embedded builds).



Tests run:

+ JPRT -- (hotspot only) to verify build-ability

+ Manually ran "jcmd $PID help GC.class_stats" on Linux/x64

+ I intend to add a new testcase once this is committed:
   https://jbs.oracle.com/bugs/browse/JDK-8006413
   Add utility classes for writing better multiprocess tests in jtreg

Thanks,
Ioi

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