On Wed, Jan 19, 2011 at 10:44 AM, Robert Haas <robertmh...@gmail.com> wrote: > Here's a new version of the patch based on some experimentation with > ideas I posted yesterday. At least on my Mac laptop, this is pretty > effective at blunting the response time spike for the first table > scan, and it converges to steady-state after about 20 tables scans. > Rather than write every 20th page, what I've done here is make every > 2000'th buffer allocation grant an allowance of 100 "hint bit only" > writes. All dirty pages and the next 100 pages that are > dirty-only-for-hint-bits get written out. Then we stop writing the > dirty-only-for-hint-bits-pages until we get our next allowance of > writes. The idea is to try to avoid creating a lot of random writes > on each scan through the table. At least here, that seems to work > pretty well - the initial scan is only about 25% slower than the > steady state (rather than 6x or more slower).
does this only impact the scan case? in oltp scenarios you want to write out the bits asap, i would imagine. what about time based flushing, so that only x dirty hint bit pages can be written out per time unit y? merlin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
