Re: [ADMIN] shared_buffers and shmmax

From: "Greg Sabino Mullane" <greg(at)turnstep(dot)com>
To: pgsql-docs(at)postgresql(dot)org
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: [ADMIN] shared_buffers and shmmax
Date: 2008-07-24 17:54:31
Message-ID: 3bd4182ebf79bc4a171f08d03d2edb2f@biglumber.com
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>> shared_buffers is in disk block size, typically 8K

> The table the OP is looking at (table 17.2 in the 8.3 docs) predates
> the ability to specify shared_buffers in KB or MB instead of
> number-of-buffers. I agree it's not entirely obvious that what it
> means is "multiply your setting in KB/MB by 8400/8192". Anybody have
> an idea how to clarify things?

Bite the bullet and start showing the buffer settings as a pure number of bytes
everywhere, and get rid of the confusing '8kB' unit in pg_settings? Things like
this don't help our cause:

test=# show shared_buffers;
shared_buffers
----------------
24MB
(1 row)

test=# set temp_buffers = '24MB';
SET

test=# show temp_buffers;
temp_buffers
--------------
3072

test=# select name, setting from pg_settings where name ~ 'buffers';
name | setting
----------------+---------
shared_buffers | 3072
temp_buffers | 3072
wal_buffers | 8

test=# show wal_buffers;
wal_buffers
-------------
64kB

--
Greg Sabino Mullane greg(at)turnstep(dot)com
End Point Corporation
PGP Key: 0x14964AC8 200807241351
http://biglumber.com/x/web?pk=2529DF6AB8F79407E94445B4BC9B906714964AC8
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