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

[Thomas Stüfe]

On Mon, Apr 1, 2019 at 4:03 PM <coleen.phillimore at oracle.com> wrote:

>
>
> 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.
>
>
Hi Coleen,

What would be the "right" way to do this? A static helper taking a
MetaspaceObj* and comparing it to NULL?

Note that we seem to compare this == NULL in a couple of places. If this is
UB those should be fixed too.

Thank you, Thomas





> 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
>
>