RFR: 8228991: Obsolete -XX:UseAdaptiveGCBoundary

[Stefan Karlsson]

Hi Kim,

On 2020-04-15 00:23, Kim Barrett wrote:
> Please review this change which obsoletes the boolean product flag
> -XX:UseAdaptiveGCBoundary and removed the supporting code.
> 
> As discussed in the associated CSR, this feature has had a long bug
> tail and does not appear to have ever really worked, so we're going
> straight to obsoleting the option and removing the code, rather than
> first deprecating it.
> 
> This mostly involves removal of a bunch of code.  In some places there
> are functions which previously needed to be virtual but no longer need
> that because the derived classes no longer exist.
> 
> There is an assertion in ParallelScavengeHeap::initialize() that was
> changed by removing !UseAdaptiveGCBoundary from a disjunction, which
> is not what one would expect if making that option unconditionally
> false.  It looks like the presence of a test for that option never
> mattered, as except in the heterogeneous heap case the virtual spaces
> have always supposed to meet (it's using AdjoiningGenerations after
> all) and did so.
>   
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8228991
> https://bugs.openjdk.java.net/browse/JDK-8242164 (CSR)
> 
> Webrev:
> https://cr.openjdk.java.net/~kbarrett/8228991/open.00/
> 

This looks good to me. If you want to push this, that's fine by me.

I found a lot of dead/unneeded code when following the trails of what 
you removed. It was too much to describe, so I created a patch for it 
instead:
https://cr.openjdk.java.net/~stefank/8228991/webrev.01/

Main change in the patch:
- Removes AdjoiningGenerations, AdjoiningVirtualSpaces, 
PSVirtualSpaceHighToLow
- Cleans up PS{Young,Old}Gen
-- Removes most virtual declarations from Removes
-- Moves PS{Young,Old}Gen initialization to constructor and makes 
initilization functions private.
-- protected -> private

Should I propose this as a follow-up cleanup?

Thanks,
StefanK


> Testing:
> mach5 tier1-5.
> Note: Unable to test nvdimm usage since we don't have any machines
> with that configuration.
>