RFR: 8047818: G1 HeapRegions can no longer be ContiguousSpaces

[Jon Masamitsu]

On 6/25/2014 4:50 AM, Mikael Gerdin wrote:
> Hi!
>
> On Monday 23 June 2014 16.26.03 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/
> Based on review comments from Jon, Stefan and Thomas (thanks!) here's a second
> version of this webrev.
>
> A quick summary of the incremental changes:
>
> * SA Support
> * taking {par_,}allocate_impl from ContiguousSpace
> * fix for building without precompiled headers
> * setting _saved_mark_word in clear()
> * initialization order problem with _top vs _bottom
> * object_iterate block_is_obj check
> * added a short specification for block_is_obj and block_size
>
> Note that the set_offset_array change was moved to the 8047820 webrev since
> it's needed to get that change to compile without precompiled headers.
>
> Full webrev:
> http://cr.openjdk.java.net/~mgerdin/8047818/webrev.1/
>
> Incremental webrev:
> http://cr.openjdk.java.net/~mgerdin/8047818/webrev.0_to_1/

Looks good.  Thanks for the changes.

Reviewed.

Jon

>
> /Mikael
>
>> Notes:
>> The moving of set_offset_range is due to an introduced circular dependency
>> between g1BlockOffsetTable.inline.hpp and heapRegion.inline.hpp
>>
>> Thanks
>> /Mikael