From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | "Ryan Hansen" <ryan(dot)hansen(at)brightbuilders(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Memory Allocation |
Date: | 2008-11-26 22:58:33 |
Message-ID: | 26199.1227740313@sss.pgh.pa.us |
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Lists: | pgsql-performance |
"Ryan Hansen" <ryan(dot)hansen(at)brightbuilders(dot)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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