On Mon, Oct 11, 2010 at 10:14 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Reduction of contention for pg_clog access, for one thing. If you read > the archives, you'll find that pg_clog access contention has been shown > to be one cause of "context swap storms".
I wonder if we could improve this with some sort of process-local cache - not to get rid of hint bits, just to reduce pg_clog contention. We might easily end up testing the same XID many times during the same table scan. Another idea that's been discussed before is to avoid writing out pages when only the hit bints have changed. Or perhaps to write them out from the background writer only, but not from backends and not when checkpointing - have a state BM_UNTIDY, which the background writer cleaning scan will treat as dirty, but which can otherwise be treated as "not dirty", so that if we start to run short of free buffers we don't hold things up writing out the hint bit updates. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
