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

[Thomas Schatzl]

On Thu, 14 Oct 2021 13:25:27 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
>
> Are there any problems with waiting a bit for this change on PR#5909?
> [Vishal] No issues. I think it would be a cleaner and better approach. 
> 
> Maybe you are also interested to try out the combination of PR#5909 and this one, allowing card table entry sizes from 128 to 1024 and any combination of region size iirc.
> [Vishal] Yes, I'll try on my end different combinations of card sizes and region sizes. I'll report my observations.
> 
> In PR#5909 there is also the question of how large regions G1 should allow with that - the patch currently allows up to 512M regions, but theoretically there is no limit - do you have any opinion on that?
> [Vishal] Currently, I have no strong opinion regarding the max. region size. I'll run specjbb2015 with different region sizes > 32m with different card sizes. I'll report if I find anything interesting.  
> 
> Thanks,
> Vishal

@vish-chan : the change for PR#5909 has finally been integrated. Sorry for the delay, things like a related bug delayed its integration more than expected.

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