RFR (M): 8027959: Investigate early reclamation of large objects in G1

Thomas Schatzl thomas.schatzl at oracle.com
Tue Jul 15 09:15:28 UTC 2014


Hi again,

On Tue, 2014-07-15 at 11:10 +0200, Thomas Schatzl wrote: 
> Hi all,
> 
>   could I have reviews for the following change that allows G1 to
> eagerly/early reclaim humongous objects on every GC?
> 
> Problem:
> 
> In G1 large objects are always allocated in the old generation,
> currently requiring a complete heap liveness analysis (full gc, marking)
> to reclaim them. 

  forgot to mention that this eager reclaim is intentionally limited to
humongous objects that do not contain references. In our tests we never
found a large (or any) amount of humongous reference arrays that were
reclaimable in this fashion.

Nevertheless there are additional CRs for improving these shortcomings
as necessary, e.g:

JDK-8048180 Investigate early reclaim of large reference arrays
JDK-8048179 Early reclaim of large objects that are referenced by a few
objects

Thanks,
  Thomas




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