Re: free space map usage - Mailing list pgsql-performance

From Tom Lane
Subject Re: free space map usage
Date
Msg-id 11798.1066158968@sss.pgh.pa.us
Whole thread Raw
In response to free space map usage  ("Jeremy M. Guthrie" <jeremy.guthrie@berbee.com>)
Responses Re: free space map usage
List pgsql-performance
"Jeremy M. Guthrie" <jeremy.guthrie@berbee.com> writes:
> Is there any way to determine how much of the free space map is currently i=
> n=20
> use?(ie. where and what it is tracking?)  I vacuum on a regular basis but I=
> =20
> never hold in terms of disk space usage.

Not in 7.3 AFAIR.  In 7.4 a full-database VACUUM VERBOSE will end with
the info you want:

regression=# vacuum verbose;
... much cruft ...
INFO:  free space map: 11 relations, 144 pages stored; 272 total pages needed
DETAIL:  Allocated FSM size: 1000 relations + 20000 pages = 178 kB shared memory.
VACUUM
regression=#

This tells me I'm only using about 1% of the FSM space (272 out of 20000
page slots).

> I jacked up the free space map=20
> pages but this doesn't appear to be working.

You know you have to restart the postmaster to make those changes take
effect, right?

            regards, tom lane

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