RFR(s): 8198553: jcmd: separate Metaspace statistics from NMT

[Thomas Stüfe]

Hi all,

may I please have reviews and a sponsor for this small change:

Issue: https://bugs.openjdk.java.net/browse/JDK-8198553
webrev:
http://cr.openjdk.java.net/~stuefe/webrevs/8198553-jcmd-separate-metaspace-stat-from-nmt/webrev.00/webrev/

Prior discussion on hotspot-runtime:
http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2018-February/026354.html
.

This patch introduces a new jcmd command, "VM.metaspace", which prints out
the metaspace statistics we before had as part of the NMT printout
(VM.native_memory). This is better because we now can print metaspace
statistics at any time regardless whether NMT is switched on or not.

Note that this does not affect the Metaspace information printed as part of
the final NMT report (-XX:+PrintNMTStatistics). That is still there.

Tested on Windows, AIX and Linux x64.

Thanks, Thomas