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
[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
