Subject: Postgresql on an AMD64 machine
From: Mark Rinaudo <mark@bowmansystems.com>
To: pgsql-performance@postgresql.org
Content-Type: text/plain
Content-Transfer-Encoding: 7bit
Date: 06 Jun 2005 12:53:40 -0500
Message-Id: <1118080420.1644.23.camel@penguin1>
Mime-Version: 1.0

I'm not sure if this is the appropriate list to post this question to
but i'm starting with this one because it is related to the performance
of Postgresql server.  I have a Penguin Computing dual AMD 64 bit
opteron machine with 8 Gigs of memory.  In my attempt to increase the
number of shared_buffers from the default to 65000 i was running into a
semget error when trying to start Postgresql. After reading the
documentation I adjusted the semaphore settings in the kernel to allow
Postgresql to start successfully.  With this configuration running if I
do a ipcs -u i get the following.

------ Shared Memory Status --------
segments allocated 1
pages allocated 30728
pages resident  30626
pages swapped   0
Swap performance: 0 attempts     0 successes

------ Semaphore Status --------
used arrays = 1880
allocated semaphores = 31928

------ Messages: Status --------
allocated queues = 0
used headers = 0
used space = 0 bytes

I'm questioning the number of semaphores being used. In order for
postgresql to start I had to set the maximum number of semaphores system
wide to 6000000. This seems to be an abnormal amount of semaphores.  I'm
curious if this is a bug in the amd64 postgresql port. Is anyone else
using postgresql on an AMD64  machine without similar issues?

TIA
Mark