Re: StrategyGetBuffer questions

On Wednesday, November 21, 2012 4:21 AM Jeff Janes wrote:
> On Tue, Nov 20, 2012 at 1:26 PM, Merlin Moncure <mmoncure@gmail.com>
> wrote:
> > In this sprawling thread on scaling issues [1], the topic meandered
> > into StrategyGetBuffer() -- in particular the clock sweep loop.  I'm
> > wondering:
> >


> >
> > *) Since the purpose of usage_count is to act on advisory basis to
> > keep recently/frequently accessed buffers from being discarded, is it
> > really necessary to rigorously guard the count with a spinlock?  If a
> > ++ or -- operation on the value gets missed here or there, how big of
> > a deal is it really?
> 
> I don't think it is all that big of a deal.
> 
> I've implemented this patch to do that.  It still applies to head.
> 
> http://archives.postgresql.org/pgsql-hackers/2011-08/msg00305.php
> 
> It was very effective at removing BufFreelistLock contention on the
> system I had at the time.

In that case, why don't we work towards reducing it?
Is the generic use case a problem or will it effect any generic scenario in
negative way?

With Regards,
Amit Kapila.