jmap -histo option in Mustang is updated to use the attach mechanism and obtain the object histogram from the target VM (in the same way as -XX:+PrintClassHistogram but output in the client side).

Mustang jmap -histo is inconsistent with Tiger jmap -histo which uses SA to examine the core file (or snapshot of a running process) which doesn't trigger a GC in the target VM.

In addition, it would be useful to get a histogram without forcing a full GC. For example, you may want to compare a histogram without a full GC and a histogram with full GC to find out what get garbage collected.

We should keep jmap -histo with no full GC and add a new option to request a full GC before iterating the heap.

-dump option also has the same issue.