the cost of logging statements

[Marcin Krol <mrkafk(at)gmail(dot)com>]

So I turned this option on:

log_statement = 'all'

..and it logs queries nicely to PostgreSQL log files. It's great for 
diagnostics & query optimization, so I'm thinking loudly - how costly in 
terms of performance would it be to have it turned on on a production 
system?

Does PostgreSQL do a sync on getting smth to log (like Linux syslog)?

If not, would the cost of that be high (apart from obvious 
considerations with disk space)?

Regards,
Marcin Krol