On 16 November 2012 01:20, Stephen Frost <sfrost@snowman.net> wrote:
> Setting it at run-time was actually my first thought on this. I'm
> disappointed to hear that it didn't work out well.
I actually did quite a lot of research on it, that was interesting,
but ultimately didn't lead to any breakthroughs. There was a couple of
research papers written on this subject in the late 80s and early 90s
that are cited in the transaction processing literature relatively
frequently, but the models involved aren't terribly applicable to
modern hardware.
This is the main paper:
http://www.hpl.hp.com/techreports/tandem/TR-88.1.pdf
This later 1991 paper reads kind of like a critique of the 1988 paper:
http://www.linux-mips.org/pub/linux/mips/people/macro/DEC/DTJ/DTJ107/DTJ107PF.PDF
There doesn't appear to be much of anything in the public domain after
this. I suppose that I could have spent more time pursuing this, but I
very much had the sense of pursuing diminishing returns. If the whole
idea of making the thing adaptive is to make it more accessible to
users, well, they'll still have to turn it on themselves (presumably
it will never be on by default), which is only slightly less effort
than following my advice here.
I suspect my tools - in particular, pgbench - just isn't sophisticated
enough to evaluate the effectiveness of any particular model. I might
have used something like Tsung, which modes workloads stochastically,
instead. However, I just didn't have the time.
--
Peter Geoghegan http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training and Services
