[9] RFR (L): 8015774: Add support for multiple code heaps

[Tobias Hartmann]

Hi,

the segmented code cache JEP is now targeted. Please review the final 
implementation before integration. The previous RFR, including a short 
description, can be found here [1].

JEP: https://bugs.openjdk.java.net/browse/JDK-8043304
Bug: https://bugs.openjdk.java.net/browse/JDK-8015774
Implementation: http://cr.openjdk.java.net/~thartmann/8015774/webrev.03/
JDK-Test fix: 
http://cr.openjdk.java.net/~thartmann/8015774_jdk_test/webrev.00/

Changes since the last review:
- Merged with other changes (for example, G1 class unloading changes [2])
- Fixed some minor bugs that showed up during testing
- Refactoring of 'NMethodIterator' and CodeCache implementation
- Non-method CodeHeap size increased to 5 MB
- Fallback solution: Store non-method code in the non-profiled code heap 
if there is not enough space in the non-method code heap (see 
'CodeCache::allocate')

Additional testing:
- BigApps (Weblogic, Dacapo, runThese, Kitchensink)
- Compiler and GC nightlies
- jtreg tests
- VM (NSK) Testbase
- More performance testing (results attached to the bug)

Thanks,
Tobias

[1] 
http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2014-April/014098.html
[2] https://bugs.openjdk.java.net/browse/JDK-8049421