RFR: 8272773: Investigate making card table size configurable [v3]

[Thomas Schatzl]

On Wed, 13 Oct 2021 20:30:33 GMT, Vishal Chand <duke at openjdk.java.net> wrote:

>> Vishal Chand has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Merge branch 'card-size-configurable' of https://github.com/vish-chan/jdk into card-size-configurable
>>  - Changes as per the first set of comments
>
> src/hotspot/share/gc/g1/g1CardTable.hpp line 79:
> 
>> 77:   static const size_t WordAllClean = SIZE_MAX;
>> 78:   static const size_t WordAllDirty = 0;
>> 79:   static const size_t LogOfMaxCardsPerRegion = BitsPerByte * sizeof(G1CardSetArray::EntryDataType);
> 
> @tschatzl Do we need this code once JDK-8275056 (Virtualize G1CardSet containers over heap region) gets integrated? From my understanding, this won't be a restriction from heap region point of view. Do I need to remove this and the changes in `g1CardTable.cpp `?

Yes. The change you will need will be very similar to https://github.com/openjdk/jdk/commit/70dcca62c4fd6657729beb3c2b985eb342b5788b (slightly modified because of review comments); but please wait until it is in. No hurry though, we'll need to complete the CSR before we can integrate anyway.

Thomas

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PR: https://git.openjdk.java.net/jdk/pull/5838