RFR: 8272773: Investigate making card table size configurable

[Thomas Schatzl]

On Fri, 8 Oct 2021 08:48:46 GMT, Vishal Chand <github.com+10235864+vish-chan at openjdk.org> wrote:

>> src/hotspot/share/gc/shared/cardTable.hpp line 234:
>> 
>>> 232:   static uintx card_shift;
>>> 233:   static uintx card_size;
>>> 234:   static uintx card_size_in_words;
>> 
>> Please do not use `uintx`; I think `uint` is just fine for those.
>
> I tried using uint, but card_size is being treated as a uintx everywhere in the code. So I'm observing compilation errors with uint.

When trying this out, at least on Linux, I found just one (already ugly) cast that needs to be "improved", in g1CollectedHeap.cpp:1664:


  // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
  // start within the first card.
  guarantee(heap_rs.base() >= (char*)(uintptr_t)G1CardTable::card_size, "Java heap must not start within the first card."); /// <--- here
  G1FromCardCache::initialize(max_reserved_regions());


Test branch at https://github.com/openjdk/jdk/compare/master...tschatzl:submit/5838-card-size-as-uint?expand=1

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