RFR(S) Contended Locking fast exit bucket (8073165)

Aleksey Shipilev aleksey.shipilev at oracle.com
Fri Mar 13 14:05:25 UTC 2015

On 03/13/2015 07:50 AM, David Holmes wrote:
>> - remove old mfence() support
> So I had expected to see this change conditional on the runtime
> processor type. But then I checked Dave's blog and saw this was
> determined 5+ years ago (!!!) so those older processors are no longer a
> consideration. I do hope the performance tests have been re-run since
> then though ;-)

MFENCE still has stronger ordering guarantees, and LOCK'ed instructions
are faster for regular accesses. Note that we also observed the
performance effects when doing blind "lock addl %(rsp), 0":


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