From: Tom Lane <tgl@sss.pgh.pa.us>
To: Ryan Hansen <ryan.hansen@brightbuilders.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Memory Allocation
Date: Wed, 26 Nov 2008 17:58:33 -0500
Message-ID: <26199.1227740313@sss.pgh.pa.us> (raw)
In-Reply-To: <011101c95013$b6fca0a0$24f5e1e0$@hansen@brightbuilders.com>
References: <011101c95013$b6fca0a0$24f5e1e0$@hansen@brightbuilders.com>
"Ryan Hansen" <ryan.hansen@brightbuilders.com> writes:
> I have a fairly robust server running Ubuntu Hardy Heron, 24 GB of memory,
> and I've tried to commit half the memory to PG's shared buffer, but it seems
> to fail. I'm setting the kernel shared memory accordingly using sysctl,
> which seems to work fine, but when I set the shared buffer in PG and restart
> the service, it fails if it's above about 8 GB.
Fails how? And what PG version is that?
FWIW, while there are various schools of thought on how large to make
shared_buffers, pretty much everybody agrees that half of physical RAM
is not the sweet spot. What you're likely to get is maximal
inefficiency with every active disk page cached twice --- once in kernel
space and once in shared_buffers.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, ryan.hansen@brightbuilders.com
Subject: Re: Memory Allocation
In-Reply-To: <26199.1227740313@sss.pgh.pa.us>
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