Re: Commitfest patches

On Fri, 2008-03-28 at 09:08 +0000, Gregory Stark wrote:

> A more invasive form of this patch would be to assign and pin a buffer when
> the preread is done. That would men subsequently we would have a pinned buffer
> ready to go and not need to go back to the buffer manager a second time. We
> would instead just "complete" the i/o by issuing a normal read call.

So if posix_fadvise did nothing or there was a longer than optimal
delay, this would be a net loss.

You'd need reasonable evidence that the posix_fadvise facility was a win
on all platforms and recent release levels before we could agree with
that.

I think we need a more thorough examination of this area before we
commit anything. Maybe you've done this, but I haven't seen the
analysis. Can you say more, please? Or at least say what you don't know,
so other experts listening can fill in the blanks.

--  Simon Riggs 2ndQuadrant  http://www.2ndQuadrant.com 
 PostgreSQL UK 2008 Conference: http://www.postgresql.org.uk