Integrated: 8306836: Remove pinned tag for G1 heap regions

[Thomas Schatzl]

On Tue, 25 Apr 2023 13:49:05 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   please review this change that removes the pinned tag from `HeapRegion`.
> 
> So that "pinned" tag for G1 heap regions indicates that the region should not move during (young) gc. This applies to now removed archive regions and humongous objects/regions.
> 
> With "real" g1 region pinning to deal with gclocker in g1 once and for all upcoming we need a refcount, a single bit is not sufficient anymore. Further there will be a naming conflict as this kind of "pinning" is different to g1 region pinning "pinning". The former indicates "contents can not be moved, but can be reclaimed", while the latter means "contents can not be moved and not reclaimed".
> 
> The (current) pinned flag is surprisingly little used, only for policy decisions.
> 
> The suggestion this change implements is to remove the "pinned" tag as it is, and reserve it for future g1 region pinning (that needs to store the pinning attribute differently as a refcount anyway).
> 
> Testing: tier1-3, gha
> 
> Thanks,
>   Thomas

This pull request has now been integrated.

Changeset: fc76687c
Author:    Thomas Schatzl <tschatzl at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/fc76687c2fac39fcbf706c419bfa170b8efa5747
Stats:     62 lines in 18 files changed: 5 ins; 31 del; 26 mod

8306836: Remove pinned tag for G1 heap regions

Reviewed-by: ayang, cjplummer, sspitsyn

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PR: https://git.openjdk.org/jdk/pull/13643