Re: [ADMIN] shared_buffers and shmmax

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: valiouk(at)yahoo(dot)co(dot)uk
Cc: pgsql-docs(at)postgreSQL(dot)org, dx k9 <bitsandbytes88(at)hotmail(dot)com>
Subject: Re: [ADMIN] shared_buffers and shmmax
Date: 2008-07-22 14:45:59
Message-ID: 28167.1216737959@sss.pgh.pa.us
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Valentin Bogdanov <valiouk(at)yahoo(dot)co(dot)uk> writes:
>> From: dx k9 <bitsandbytes88(at)hotmail(dot)com>
>> I'm trying to understand what the documentation means
>> by bytes per increment, what is the increment supposed to
>> be bytes, MB, or Kb.

> shared_buffers is in disk block size, typically 8K, at least that's what it is on Linux platforms. shmmax is quite simply in bytes.

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?

regards, tom lane

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