RFR (S) 8019968: Reference CAS induces GC store barrier even on failure (original) (raw)

Andrew Dinn adinn at redhat.com
Wed Jul 29 09:24:38 UTC 2015

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On 29/07/15 09:58, Aleksey Shipilev wrote:

I would like to suggest a fix for: https://bugs.openjdk.java.net/browse/JDK-8019968

In short, current reference CAS intrinsic blindly emits postbarrier, ignoring the CAS result. In some cases, notably contended CAS spin-loops, we fail the CAS a lot, and thus go for a postbarrier excessively. Instead, we can conditionalize on the result of the store itself, and put the postbarrier only on success path: http://cr.openjdk.java.net/~shade/8019968/webrev.01/ More performance results here: http://cr.openjdk.java.net/~shade/8019968/notes.txt

Nice! The code looks fine and your test results are very convincing. I'll be interested to see how this looks on AArch64.

That said, I am afraid you still need a Reviewer!

regards,

Andrew Dinn

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