[concurrency-interest] RFR: 8065804: JEP 171: Clarifications/corrections for fence intrinsics

Andrew Haley aph at redhat.com
Wed Dec 10 16:02:39 EST 2014


On 12/05/2014 09:49 PM, Martin Buchholz wrote:
> The actual implementations of storestore (see below) seem to
> universally give you the stronger ::release barrier, and it seems
> likely that hotspot engineers are implicitly relying on that, that
> some uses of ::storestore in the hotspot sources are bugs (should be
> ::release instead) and that there is very little potential performance
> benefit from using ::storestore instead of ::release, precisely
> because the additional loadstore barrier is very close to free on all
> current hardware.

That's not really true for ARM, where the additional loadstore requires
a full barrier.  There is a good use for a storestore, which is when
zeroing a newly-created object.

Andrew.



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