Tom Lane escribió: > Alvaro Herrera <alvherre@xxxxxxxxxxxxxxxxx> writes: > > Tom Lane escribi� >> Reorder to what, though? You still have the problem that we don't know > >> much about the physical layout on-disk. > > > Well, to block numbers as a first step. > > fsync is a file-based operation, and we know exactly zip about the > relative positions of different files on the disk. Doh, right, I was thinking in the sync-file-range kind of API. > > We had a customer that had a > > performance problem because they were inserting lots of data to TOAST > > tables, causing very frequent extensions. I kept wondering whether an > > allocation policy that allocated several new blocks at a time could be > > useful (but I didn't try it). This would also alleviate fragmentation, > > thus helping the physical layout be more similar to logical block > > numbers. > > That's not going to do anything towards reducing the actual I/O volume. > Although I suppose it might be useful if it just cuts the number of > seeks. Oh, they had no problems with I/O volume. It was relation extension lock that was heavily contended for them. -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
