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

[Erik Helin]

Hi Harold,

thanks for reviewing!

Erik

On 2013-09-04, harold seigel wrote:
> Hi Erik,
> 
> I looked into this a bit.  You are correct in saying "has no effect".
> 
> Sorry,  Harold
> 
> On 9/4/2013 2:13 PM, harold seigel wrote:
> >Hi Erik,
> >
> >These changes look good.  Just a small nit.  In arguments.cpp, I
> >think the new warning should say "has no affect" instead of "has
> >no effect".
> >
> >Thanks, Harold
> >
> >On 9/4/2013 1:36 PM, 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/
> >>
> >>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
> >
>