[9] RFR(XS): 8176513 Poor code quality for ByteBuffers

Vladimir Kozlov vladimir.kozlov at oracle.com
Wed Mar 15 15:05:29 UTC 2017

Good for JDK 9. Since Vladimir I. suggested the fix I assume he reviewer too.

Roland, did you get ByteBuffers some performance back?

I will need to run pre-integration testing before pushing.


On 3/15/17 2:48 AM, Roland Westrelin wrote:
> http://cr.openjdk.java.net/~roland/8176513/webrev.01/
> This changes relaxes the condition under which MemBarCPUOrder nodes are
> added around unsafe accesses. If the object being accessed is an array
> and the access is mismatched, the current code add useless barriers
> (there's only one memory slice for the entire array so no risk of
> breaking alias analysis). If the base is not known to be not null,
> membars are added as well. These membars are not added for arrays in 8u
> and that hasn't caused any known problem. So in order to keep this
> change simple, we propose removing that condition (this was suggested by
> Vladimir Ivanov in the comments for this bug).
> Roland.

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