[concurrency-interest] Unsafe.getAndAddLong

Andrew Haley aph at redhat.com
Thu May 22 14:15:48 EDT 2014


On 05/22/2014 06:51 PM, Nathan Reynolds wrote:
> I am curious.  How much does the load barrier cost?  The CAS can't 
> execute until the load completes anyways.  In other words, there is a 
> data dependency there.

That's an excellent point.  I confess that I don't really know: I
assume that it might generate an extra bus transaction, but at best
it'll be completely free because it's in the shadow of the load.  It's
very hard for me to say for certain because there are (or will be)
several versions of this architecture, with different design goals.

Andrew.



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