Integrated: Scan remembered

[Kelvin Nilsen]

On Fri, 8 Jan 2021 17:56:02 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

> Add support for scanning remembered set
> 
> The code has support for two alternative implementations of the remembered set. The current remembered set implementation uses traditional card marking, where the post writer barrier for pointer write operations sets the mark for every overwritten card.
> 
> A contemplated future remembered set implementation is represented in skeleton form within the shenandoahBufferWithSATBRememberedSet.hpp and shenandoahBufferWithSATBRememberedSet.inline.hpp files. The idea of this alternative remembered set implementation is that the existing SATB buffers will be augmented to additionally remember the address of each overwritten reference field. Subsequent processing of the SATB buffer contents by background GC threads will update the TBD remembered set representation.
> 
> There are known bugs and performance improvements in the remembered set scanning implementation that have been addressed in certain Amazon-internal commits. These commits will be upstreamed at a later time after other commits not directly related to remembered set scanning are upstreamed.

This pull request has now been integrated.

Changeset: 8a38a9ed
Author:    Kelvin Nilsen <kdnilsen at openjdk.org>
Committer: Roman Kennke <rkennke at openjdk.org>
URL:       https://git.openjdk.java.net/shenandoah/commit/8a38a9ed
Stats:     1552 lines in 9 files changed: 1526 ins; 11 del; 15 mod

Scan remembered

Reviewed-by: rkennke, zgu

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PR: https://git.openjdk.java.net/shenandoah/pull/12