I'm not sure if blocks reffered from all WAL records in single WAL segment can fit kernel cache. This is why current pg_readahead returns the last LSN and require starting LSN. So far, with FPW, it seems that we can prefetch all the pages in a WAL segment. So it will be okay for archive log compressed with pg_compresslog. I'll test if it's okay in the case full_page_writes=off.
Anyway, I'd like to keep my proposal for 8.4 and continue the test and evaluation to report to the mailing list. I'll also change the whole code to run in the core. ------- Koichi Suzuki 2008/10/29 Simon Riggs <[EMAIL PROTECTED]>: > > On Wed, 2008-10-29 at 09:55 +0900, Koichi Suzuki wrote: > >> I'd like to hear some more about these. I'm more than happy to write >> all the code inside PG core to avoid overhead to create another >> process. > > Having an external program can help earlier releases also, so I think > this is the right approach for now. > > In next PG release we should bring this into core, along with streaming. > > Interface would be better if it accepted > pg_readahead filename > or pg_readahead filename start-lsn > > We don't always need a starting lsn. > > -- > Simon Riggs www.2ndQuadrant.com > PostgreSQL Training, Services and Support > > -- ------ Koichi Suzuki -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
