RFR: JDK-8310111: Shenandoah wastes memory when running with very large page sizes [v2]

[Thomas Stuefe]

On Fri, 30 Jun 2023 13:23:25 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> 
> > My proposal would be: as you propose, use one RS. Then:
> > * static huge pages - no uncommit, no problem
> > * THP: never uncommit, all stays committed, no problem
> > * Non-LP: we use tiny system pages. Align the mark bitmap start to system page size, then all works as it did before.
> 
> Would still be nice to support slice uncommit with THP, at least for smaller 2M pages. Aligning marking bitmaps to 2M does not seem to waste a lot of memory, and our footprint is still much better with uncommits.

Okay, lets do that. I can just let the marking bitmaps live at the front of the RS, then the first is already aligned.

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PR Comment: https://git.openjdk.org/jdk/pull/14559#issuecomment-1614899136