RFR: 8175561: Memory churn in jimage code affects startup after resource encapsulation changes

[Claes Redestad]

Hi,

various resource encapsulation changes in 9+148 meant an uptick in
footprint and startup times for certain applications.

While some of this regression is hard to avoid[1] (opening readers,
touching more memory mapped pages etc), a large part is due to simple
java allocation churn, some of which can be optimized away by reducing
the number of objects we create when scanning modules for resources.

Bug: https://bugs.openjdk.java.net/browse/JDK-8175561
Webrev: http://cr.openjdk.java.net/~redestad/8175561/jdk.01/

Thanks!

/Claes

[1] Things we could do in the future to improve further include adding
an index to the jimage (too late for 9) or marking modules with no 
non-encapsulated resources as such so that they can be skipped.