[aarch64-port-dev ] Question about JVM option "-XX:+UseBarriersForVolatile" usage in aarch64.

[Andrew Haley]

On 4/7/20 5:05 PM, Derek White wrote:
> I think we should no longer enable UseBarriersForVolatile for the prototype ThunderX processors (model A1, variant 0). We believe that these should all have been replaced or decommissioned. We can add an error at startup if we detect that CPU.
> 
> Processor support is independent of whether UseBarriersForVolatile should be kept for debugging & development.
> 
> On that issue, in addition to the support being broken and not regularly tested, I think that this adds a veneer of complexity to already subtle code. Especially since about half of the uses of UseBarriersForVolatile are of the form "if not using extra barriers, add a barrier" ��. I'd be fine with seeing it go.

OK, thanks.

One other use of UseBarriersForVolatile was as a fallback when HotSpot
changes broke the use of ldar/stlr for volatile. Andrew Dinn, so you think
we still need it as a fallback in case ldar/stlr handling breaks again?

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
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