Re: BUG #3801: max_fsm_pages postgresql.conf default != guc.c default

Kris-

Thanks for digging into the code for that. Unfortunately, I'm now more
confused.

> the actual default at initdb time can be set as high as nbuffers *
> 50,
> where the max shared_buffers is 4096. So the default max_fsm_pages
> for a
> beefier machine will be 204800 which is what you will find in
> postgresql.conf.sample.

The initdb was done on an 8-way Opteron with 32GB of RAM. I would have
assumed that this satisfied the definition of a "beefier machine", but I
got the measly 20000 m_f_p setting (and didn't manually change the
shared_buffers setting). Initdb was done with 8.2.3 IIRC.

> The fact that you have a commented out value in your postgresql.conf
> does
> not mean it is the default.

Really? Comments in postgresql.conf file sayeth:

# The
# commented-out settings shown in this file represent the default
values.
#
# Please note that re-commenting a setting is NOT sufficient to revert
it
# to the default value, unless you restart the server.

This seems to directly say that the commented out settings are the
default values, and furthermore that one must restart to get the
indicated default back. Based on your evidence, it seems that the
postgresql.conf comment for max_fsm_pages needs revising to indicate
that the m_f_p default is determined at initdb-time.

Thank you,
Reece

--
Reece Hart, http://harts.net/reece/, GPG:0x25EC91A0