RFR (M): 8213229: Treat StringTable as weak in G1 young collections

[Thomas Schatzl]

Hi again,

  I am retracting this RFR for now - Kim asked to have the string table
processing hooked up directly to the WeakProcessor, and completely
handle it there instead of potentially doing this in two steps.

Thanks,
  Thomas

On Tue, 2018-12-18 at 17:20 +0100, Thomas Schatzl wrote:
> Hi all,
> 
>   can I have reviews that treat the string table as weak during young
> gc (too)?
> 
> The change itself is pretty straightforward, i.e. not processing the
> string table as roots (if ClassUnloading is true - this seems to be
> the commonly used flag to turn this off), and at the end in some
> parallel phase purge the string table itself.
> 
> Unfortunately this incurred some changes to the parallel cleaning
> tasks to allow doing this parallel phase in conjunction with string
> deduplication to avoid the additional worker thread startup, and
> share some code, which rippled through the code a bit.
> 
> However this also makes it a bit easier imho to join other parallel
> phases like the weak handle processing during the post evacuation
> phase into this "partial cleanup" in follow-ups.
> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8213229
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8213229/webrev/
> Testing:
> hs-tier1-5, gc/shenandoah for shenandoah
> 
> Thanks,
>   Thomas
> 
>