Re: Page-at-a-time Locking Considerations

On Mon, 2008-02-04 at 18:08 -0300, Alvaro Herrera wrote:
> Simon Riggs wrote:
> > On Mon, 2008-02-04 at 20:03 +0000, Gregory Stark wrote:
> > 
> > > I wonder how hard it would be to shove the clog into regular shared
> > > memory pages and let the clock sweep take care of adjusting the
> > > percentage of shared mem allocated to the clog versus data pages.
> > 
> > There is a reason that's not been done... try it and see.
> 
> What is it?

Time to locate a block differs in the two cases. clog requires a search
of data on 1 cache line, which isn't often changed. shared_buffers
requires a hash table search on a volatile data structure.

--  Simon Riggs 2ndQuadrant  http://www.2ndQuadrant.com