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

[David Holmes]

On 11/12/2014 7:02 AM, Andrew Haley wrote:
> 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.

There are many good uses of storestore in the various lock-free 
algorithms inside hotspot.

David

> Andrew.
>