Re: [ADMIN] shared_buffers and shmmax

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: valiouk(at)yahoo(dot)co(dot)uk, pgsql-docs(at)postgresql(dot)org, dx k9 <bitsandbytes88(at)hotmail(dot)com>
Subject: Re: [ADMIN] shared_buffers and shmmax
Date: 2008-12-15 23:23:02
Message-ID: 200812152323.mBFNN3Y25121@momjian.us
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Tom Lane wrote:
> [ redirecting to pgsql-docs ]
>
> 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?

I have updated the table title to be clearer.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ If your life is a hard drive, Christ can be your backup. +

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