RFR: 8015107: NPG: Use consistent naming for metaspace concepts

[Erik Helin]

On 2013-09-05, Mikael Gerdin wrote:
> Erik,
> 
> On 2013-09-04 19:36, Erik Helin wrote:
> >Hi all,
> >
> >this patch changes the name of two flags:
> >- -XX:+UseCompressedKlassPointers becomes
> >   -XX:+UseCompressedClassPointers (note the 'K' instead of the 'C')
> >- -XX:ClassMetaspaceSize becomes -XX:CompressedClassSpaceSize
> >
> >Background:
> >These two flags were introduced when metaspace was merged into hs25.
> >To use a smaller size for the Java object headers, the pointer in the
> >object header that points to the Klass instance for the object can be 32
> >bits on a 64-bit system. Such pointers has been called compressed klass
> >pointers. This is the same concept as compressed oops.
> >
> >For the current implementation of compressed class pointers to work, the
> >Klass instances need to be placed in a continuous virtual memory space.
> >This virtual memory space was called ClassMetaspace but this patch
> >introduces the name CompressedClassSpace to emphasize that the concept
> >is closely related to compressed klass pointers.
> >
> >The 'K' in the CompressedKlassPointers and CompressedClassSpace was
> >changed to a 'C' since the C++ class Klass is an implementation detail
> >that we do not want to expose to the users.
> >
> >I've also added a check in Arguments::parse that checks if the user has
> >set CompressedClassSpaceSize when compressed class pointers
> >are _not_ used. If this is the case, then the VM will print a warning. I've
> >also added a test that verifies this actually happens.
> >
> >The change touches a lot of files, but the change in each file is very
> >small.
> >
> >Webrev:
> >http://cr.openjdk.java.net/~ehelin/8015107/webrev.00/
> 
> Thanks for taking care of this.
> Change looks good to me.

Thanks!

Erik

> /Mikael
> 
> >
> >Bug:
> >http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8015107
> >
> >Testing:
> >- JPRT
> >- The jtreg tests in hotspot/test
> >- Newly added jtreg test
> >
> >Thanks,
> >Erik
> >