Integrated: 8254028: G1 incorrectly updates scan_top for collection set regions during preparation of evacuation

[Thomas Schatzl]

On Thu, 8 Oct 2020 08:52:20 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   can I have reviews for this change that makes values of G1RemSetScanState::_scan_top for regions in the initial
>   collection set consistent with ones in optional collection set?
> So currently G1RemSetScanState::_scan_top is top() for regions in the initial collection set although they will never
> be scanned as enforced when dropping the remsets onto the card table. For the optional collection set, G1 sets scan_top
> manually to NULL when selecting the next few optional regions (using G1RemSet::exclude_region_from_scan()).  When
> debugging this discrepancy recently posed some slight surprise for me, so I would like to change this. Also there is
> some risk that future code that relies on that property will be surprised.  Testing: tier1-4; lots of kitchensink runs
> with JDK-8254164.
> Thanks,
>   Thomas

This pull request has now been integrated.

Changeset: bf46acf9
Author:    Thomas Schatzl <tschatzl at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/bf46acf9
Stats:     21 lines in 2 files changed: 15 ins; 0 del; 6 mod

8254028: G1 incorrectly updates scan_top for collection set regions during preparation of evacuation

Reviewed-by: kbarrett

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PR: https://git.openjdk.java.net/jdk/pull/557