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 (original) (raw)

Jon Masamitsu jon.masamitsu at oracle.com
Mon Mar 21 03:04:23 UTC 2016

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.

Thanks.

Jon

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