[PERFORM] effective cache size on FreeBSD (WAS: Performance on SUSE w/ reiserfs)
I have a postgresql 7.4.8-server with 4 GB ram. #effective_cache_size = 1000# typically 8KB each This is computed by sysctl -n vfs.hibufspace / 8192 (on FreeBSD). So I changed it to: effective_cache_size = 27462# typically 8KB each Apparently this formula is no longer relevant on the FreeBSD systems as it can cache up to almost all the available RAM. With 4GB of RAM, one could specify most of the RAM as being available for caching, assuming that nothing but PostgreSQL runs on the server -- certainly 1/2 the RAM would be a reasonable value to tell the planner. (This was verified by using dd: dd if=/dev/zero of=/usr/local/pgsql/iotest bs=128k count=16384 to create a 2G file then dd if=/usr/local/pgsql/iotest of=/dev/null If you run systat -vmstat 2 you will see 0% diskaccess during the read of the 2G file indicating that it has, in fact, been cached) Thank you for your reply. Does this apply to FreeBSD 5.4 or 6.0 on amd64 (or both)? regards Claus ---(end of broadcast)--- TIP 2: Don't 'kill -9' the postmaster
Re: [PERFORM] effective cache size on FreeBSD (WAS: Performance on SUSE w/ reiserfs)
On Oct 11, 2005, at 10:54 AM, Claus Guttesen wrote: Thank you for your reply. Does this apply to FreeBSD 5.4 or 6.0 on amd64 (or both)? It applies to FreeBSD = 5.0. However, I have not been able to get a real answer from the FreeBSD hacker community on what the max buffer space usage will be to properly set this. The `sysctl -n vfs.hibufspace` / 8192 estimation works very well for me, still, and I continue to use it. ---(end of broadcast)--- TIP 6: explain analyze is your friend
