Request for Review (s) - 8060463: ParNew: SurvivorAlignmentInBytes greater then YoungPLABSize cause assert(obj != NULL || plab->words_remaining() < word_sz) failed: Else should have been able to allocate

Thomas Schatzl thomas.schatzl at oracle.com
Thu Mar 24 12:14:19 UTC 2016


Hi Jon,

On Sun, 2016-03-20 at 20:04 -0700, Jon Masamitsu wrote:
> If SurvivorAlignmentInBytes is larger than the size of the promotion
> LAB an allocation aligned to SurvivorAlignmentInBytes  may fail. The
> allocation of the PLAB depends of the size of the object being
> allocated and if the PLAB is successfully allocated the allocation
> of the object should succeeded (and is checked by an assertion).
> For alignments larger than  PLAB, a larger PLAB is sometimes needed
> to allow for the alignment.
> 
> The fix does not try to avoid the need for a new PLAB at the
> next promotion by making the PLAB even larger.  The large
> values of SurvivorAlignmentInBytes  are allowed but not
> expected.  I chose not to make the PLAB even larger for a
> situation I don't expect to see in practice.
> 
> https://bugs.openjdk.java.net/browse/JDK-8060463
> http://cr.openjdk.java.net/~jmasa/8060463/webrev.00/
> 
> Tested with the newly added test which check a range
> of SurvivorAlignmentInBytes values.

  looks good sans Sangheon's comments.

Thanks,
  Thomas


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