Re: testing HS/SR - 1 vs 2 performance

On Sat, 2010-04-17 at 18:52 -0400, Tom Lane wrote:
> Simon Riggs <simon@2ndQuadrant.com> writes:
> > What I'm not clear on is why you've used a spinlock everywhere when only
> > weak-memory thang CPUs are a problem. Why not have a weak-memory-protect
> > macro that does does nada when the hardware already protects us? (i.e. a
> > spinlock only for the hardware that needs it).
> 
> Well, we could certainly consider that, if we had enough places where
> there was a demonstrable benefit from it.  I couldn't measure any real
> slowdown from adding a spinlock in that sinval code, so I didn't propose
> doing so at the time --- and I'm pretty dubious that this code is
> sufficiently performance-critical to justify the work, either.

OK, I'll put a spinlock around access to the head of the array.

Thanks for your input.

-- Simon Riggs           www.2ndQuadrant.com