very slow perm gen verification

[John Coomes]

When running some nsk tests, I saw several timeouts which appear to be
due to very slow verification of the perm gen (i.e., 10+ minutes to
verify a 64MB perm gen (par scavenge)), which is done as the jvm is
exiting.  Happens frequently, but not every time; and w/my changes as
well as w/jdk7-b141.

I vaguely recall some discussion of this a few months ago, but can't
find any record of it :-(.  Sound familiar to anyone?

-John