On 2007-02-21, Mark Kirkwood <markir@xxxxxxxxxxxxxxx> wrote: > With respect to 'select count(*) from ...' being slower on FreeBSD, > there are a number of things to try to make FreeBSD faster for this sort > of query. Two I'm currently using are: > > - setting sysctl vfs.read_max to 16 or 32 > - rebuilding the relevant filesystem with 32K blocks and 4K frags Be aware that increasing the filesystem block size above 16k is _known_ to tickle kernel bugs - there is a workaround involving increasing BKVASIZE, but this isn't a config parameter and therefore you have to patch the sources. The symptom to look for is: largescale filesystem deadlocks with many processes (especially syncer) blocked in "nbufkv" state. -- Andrew, Supernews http://www.supernews.com - individual and corporate NNTP services
