RFR(S): 8223575: add subspace transitions to gc+metaspace=info log lines

[Tony Printezis]

Any chance of someone taking a look at this?

http://cr.openjdk.java.net/~tonyp/8223575/webrev.0/

As I said on the JIRA, users can be confused when they metaspace capacity
shows as over 1G even though they asked for 128M. Breaking down the spaces,
when coops are enabled, can address this confusion (and having the actual
occupancy of each space separately is also a lot more informative and
avoids guesswork). The output looks like this when coops are enabled:

[10.090s][info][gc,metaspace     ] GC(8) Metaspace: 2130K->2130K(1056768K)
ClassMetadata: 1906K->1906K(8192K) ClassSpace: 223K->223K(1048576K)

and like this (i.e., what it was before the change) when coops are not
enabled:

[25.767s][info][gc,metaspace     ] GC(28) Metaspace: 8107K->8107K(10240K)

A couple of notes on the changes:

- I’m open to different suggestions for what to call ClassMetadata and
ClassSpace. :-)
- I didn’t know where to put the HEAP_CHANGE_FORMAT and
HEAP_CHANGE_FORMAT_ARGS macros, so that they can be easily shared, and I
ended up putting them in heap.hpp. Let me know if there’s a better place
for them.

Tony


—————
Tony Printezis | @TonyPrintezis | tprintezis at twitter.com
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