[cpp-threads] Alternatives to SC

[Paul E. McKenney]

On Tue, Jan 16, 2007 at 10:04:12AM -0500, Doug Lea wrote:
> One broader issue hiding in...
> 
> Paul E. McKenney wrote:
> >  Raul's version has the advantage of
> >permitting the caches to retain read sharing.
> 
> As the number of CPUs increase, it is nearly always better
> to stall only one processor waiting out a barrier rather
> than to stall an unknown number of them for an unknown
> period as they fight for exclusive cache line access to perform
> an LL/SC or CAS.
> 
> This is one part of the reason that concurrent readability
> (i.e., CCCC, but not necessarily SC semantics) is so important
> for scalability. Standardized specs will need to be sensible
> in the upcoming years when having hundreds of processors is not
> uncommon.

What he said!!!  Hear, hear!!!

						Thanx, Paul