RFR(s): 8221539: [metaspace] Improve MetaspaceObj::is_metaspace_obj() and friends

[coleen.phillimore at oracle.com]

http://cr.openjdk.java.net/~stuefe/webrevs/8221539--%5bmetaspace%5d-improve-metaspaceobj--is_metaspace_obj()-and-friends/webrev.00/webrev/src/hotspot/share/memory/allocation.cpp.udiff.html

Apparently comparing this == NULL or other values is undefined 
behaviour.  Luckily, I think there's just one call that can be made static.

The rest looks good.
Coleen



On 3/27/19 5:01 PM, Thomas Stüfe wrote:
> Hi all,
>
> May I please have reviews for this small optimization:
>
> cr:
> http://cr.openjdk.java.net/~stuefe/webrevs/8221539--%5bmetaspace%5d-improve-metaspaceobj--is_metaspace_obj()-and-friends/webrev.00/webrev/index.html
> Issue: https://bugs.openjdk.java.net/browse/JDK-8221539
>
> There are several functions which, given an unknown pointer assumed to be a
> metaspace object, check if the pointer is indeed a metaspace object by
> walking the VirtualSpaceList and checking ranges.
>
> This patch adds checks which weed out the obvious cases to avoid needlessly
> walking the vs list.
>
> Patch also adds verifications for the VirtualSpaceList in debug cases.
> Those run only when a new node has been added to the list, or when a node
> has been purged, so very sparingly.
>
> When purging nodes, I removed a small unnecessary and inefficient check
> which checked whether (one of the) purged nodes was still in the list.
> Since we now as part of the new VirtualSpaceNode::verify() walk this list,
> the check is unnecessary.
>
> Thanks, Thomas