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

[Thomas Schatzl]

On Fri, 8 Oct 2021 08:38:39 GMT, Vishal Chand <duke at openjdk.java.net> wrote:

>> src/hotspot/share/gc/parallel/objectStartArray.hpp line 57:
>> 
>>> 55:   static uint block_shift;
>>> 56:   static uint block_size;
>>> 57:   static uint block_size_in_words;
>> 
>> I *think* the naming guideline for static members is the same as for regular class members, i.e. use an underscore in front. Maybe wait on changing this for another person to comment on (I did not look up the style guide).
>> We do not use public static members too often :)
>
> Actually I've kept the names of all the pre-existing constants (which are now variables) same as before. Otherwise we have to change all the references also.

Let's see what the second reviewer thinks. Otherwise this can be done separately as it might hide the interesting part of this change.

>> src/hotspot/share/gc/shared/cardTable.cpp line 468:
>> 
>>> 466: uintx CardTable::ct_max_alignment_constraint() {
>>> 467:   // CardTable max alignment is computed with card_size_max
>>> 468:   return card_size_max * os::vm_page_size();
>> 
>> I think this change causes some tests to fail because their heap will get too large. Maybe it is possible to move code so that the actual card size value is used here to avoid this, or fix the errors (will be visible with enabled github actions).
>
> I don't see any errors after enabling the tests via github actions. Am I missing something here?

I'll re-check.

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