RFR: 8087200: Code heap does not use large pages

[Erik Helin]

Hi all,

this patch fixes an issue with the page sizing in in the code heap
in 8u60 that was introduced in the backport for JDK-8049864. The issue does
not exist in JDK 9 because the code heap in JDK 9 has been rewritten and
uses the VirtualSpace to decide the page size for the reserved size
(there is still an issue with the alignment of the comittted size in JDK
9, see JDK-8087339 [0]).

The fix for 8u60 consists of using the reserved size to determine the
page size (and not require that the page size divides the reserved
size, because the reserved size will be aligned to the page size later
anyway).

Webrev:
http://cr.openjdk.java.net/~ehelin/8087200/webrev.00/

Bug:
https://bugs.openjdk.java.net/browse/JDK-8087200

Testing:
- JPRT
- Ad-hoc:
  - Bigapps:
    - Kitchensink
    - runThese
    - Weblogic
  - JTReg:
    - JDK
    - SVC
  - NSK
- Confirmed that the perf regression introduced with the backport of [0]
  went away.

Thanks,
Erik

[0]: https://bugs.openjdk.java.net/browse/JDK-8087339