On Mon, 2005-01-03 at 17:14, Tom Lane wrote: > Simon Riggs <[EMAIL PROTECTED]> writes: > > The situation where another backend requests the block immediately > > before the I/O is fairly common AFAICS, especially since > > StrategyGetBuffer ignores the BM_DIRTY flag in selecting victims. > > How do you figure that? StrategyGetBuffer won't return the same buffer > again (because dirty or not, it'll be pinned by the time anyone else > gets to run StrategyGetBuffer). The case we are interested in is where > someone suddenly wants the original page again --- that is, a page that > was just about to fall off the back end of the freelist is wanted again. > I don't see that that case is common, especially not with a reasonably > large shared_buffer setting, and most especially not when the bgwriter > is doing its job and keeping the back end of the freelist clean.
Yes, what I was effectively arguing for was to tune for the case where shared_buffers is still at the default...which is of course fairly pointless, since the way to tune is just to increase shared_buffers. ...Fully agree with your original suggestion now. -- Best Regards, Simon Riggs ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
