Re: Performance on SUSE w/ reiserfs

From: Claus Guttesen <kometen(at)gmail(dot)com>
To: Jon Brisbin <jon(dot)brisbin(at)npcinternational(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Performance on SUSE w/ reiserfs
Date: 2005-10-11 07:41:32
Message-ID: b41c75520510110041j4b3d4017y@mail.gmail.com
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I have a postgresql 7.4.8-server with 4 GB ram.

> #max_fsm_pages = 20000 # min max_fsm_relations*16, 6 bytes each
> #max_fsm_relations = 1000 # min 100, ~50 bytes each

If you do a vacuum verbose (when it's convenient) the last couple of
lines will tell you something like this:

INFO: free space map: 143 relations, 62034 pages stored; 63792 total
pages needed
DETAIL: Allocated FSM size: 300 relations + 75000 pages = 473 kB shared memory.

It says 143 relations and 63792 total pages needed, so I up'ed my
values to these settings:

max_fsm_relations = 300 # min 10, fsm is free space map, ~40 bytes
max_fsm_pages = 75000 # min 1000, fsm is free space map, ~6 bytes

> #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

Bear in mind that this is 7.4.8 and FreeBSD so these suggestions may
not apply to your environment. These suggestions could be validated by
the other members of this list.

regards
Claus

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