Heikki,
It's important to distinguish what kind of fadvise we're talking about. The bitmap scan code issues hints about individual pages, using posix_fadvise(... POSIX_FADV_WILLNEED). For increasing the readahead of a sequential scan, you'd want to use POSIX_FADV_SEQUENTIAL. I believe the support for the latter is much more widespread than for the former.
OK, so this is potentially useful (pending testing) but it's a different feature. We'll discuss it for 8.5.
The other thing I was going to ask you about is using posix_fadvise as an alternative to O_DIRECT for the xlog. O_DIRECT is, AFAIK, linux-only, whereas there are "direct write" fadvise flags which work on multiple OSes.
-- Josh Berkus PostgreSQL Experts Inc. www.pgexperts.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
