RFR: 8047818: G1 HeapRegions can no longer be ContiguousSpaces

Jon Masamitsu jon.masamitsu at oracle.com
Tue Jun 24 14:26:52 UTC 2014


Did you consider creating a base class for ContiguousSpace and
G1OffsetTableContigSpace that has a  _top but does not assume

Could allocate_inner() have been called allocate_impl() as it is
in ContiguousSpace?  I don't know what the "inner" in the name
is telling me.

I've just started on the review so more to come.


On 06/23/2014 07:26 AM, Mikael Gerdin wrote:
> Hi!
> When G1 is modified to unload classes without doing full collections the old
> HeapRegions can contain unparseable objects. This makes ContiguousSpace
> unsuitable as a base class for HeapRegion since it assumes that all objects
> below _top are parseable.
> Modify G1OffsetTableContigSpace to implement allocation with a separate _top
> and reimplement some Space pure virtuals to make object iteration work as
> expected.
> This change is the last part of a set of 4 changes: 8047818, 8047819, 8047820,
> 8047821 which are needed to refactor the HeapRegion class and its superclasses
> in order to simplify the G1 class unloading change which is coming.
> This change depends on the 19, 20 and 21 changes.
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8047818
> Webrev:
> http://cr.openjdk.java.net/~mgerdin/8047818/webrev/
> Notes:
> The moving of set_offset_range is due to an introduced circular dependency
> between g1BlockOffsetTable.inline.hpp and heapRegion.inline.hpp
> Thanks
> /Mikael

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