RFR: 8015107: NPG: Use consistent naming for metaspace concepts
mikael.gerdin at oracle.com
Thu Sep 5 09:08:26 PDT 2013
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
> 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
Thanks for taking care of this.
Change looks good to me.
> - JPRT
> - The jtreg tests in hotspot/test
> - Newly added jtreg test
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