RFR: 8305896: Alternative full GC forwarding [v25]

[Thomas Schatzl]

On Wed, 3 May 2023 21:30:31 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix type narrowing
>
> src/hotspot/share/gc/shared/slidingForwarding.inline.hpp line 43:
> 
>> 41: 
>> 42: uint SlidingForwarding::region_index_containing(HeapWord* addr) {
>> 43:   uint index = static_cast<uint>(pointer_delta(addr, _heap_start) >> _region_size_words_shift);
> 
> I believe it is possible to bias the array pointer to avoid that subtraction of the `_heap_start` like we do e.g. for the card table. See also `G1BiasedArray` or so for a kind of ready-made class implementing this.
> 
> Not sure it will help a lot, but at least remove the subtraction and the load of the `_heap_start` value.

Maybe possible ;)

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PR Review Comment: https://git.openjdk.org/jdk/pull/13582#discussion_r1184338484