From: Mark Kirkwood <markir@paradise.net.nz>
To: Cosimo Streppone <cosimo@streppone.it>
Cc: Postgresql Performance <pgsql-performance@postgresql.org>
Subject: Re: postgresql-8.0.1 performance tuning
Date: Wed, 01 Jun 2005 19:22:42 +1200
Message-ID: <429D6242.6000804@paradise.net.nz> (raw)
In-Reply-To: <429D5942.6020502@streppone.it>
References: <1117201312.7060.6.camel@fandelm.ecommit.de>
<429D47FD.7090501@streppone.it>
<429D56B2.9070302@paradise.net.nz>
<429D5942.6020502@streppone.it>
Cosimo Streppone wrote:
> Mark Kirkwood ha scritto:
>
>> Cosimo Streppone wrote:
>>
>>> ######### Config ############
>>>
>>>> /etc/sysctl.conf:
>>>> kernel.shmall = 786432000
>>>> kernel.shmmax = 786432000
>>>
>>>
>>> I think you have a problem here.
>>> kernel.shmmax should *not* be set to an amount of RAM, but
>
>
> Sorry, I thought "shmall" but written "shmmax".
> Thanks Mark!
>
Hehe - happens to me all the time!
On the shmall front - altho there is *probably* no real performance
impact setting it to the same as shmmax (i.e. allowing 4096 allocations
of size shmmax!), it is overkill. In addition it does allow for a DOS by
a program that allocates thousands of segments (or somehow starts
thousands of Pg servers on different ports...)!
For a dedicated Pg server I would size shmall using a calculation along
the lines of:
shmall = (no. of postgresql servers) * (shmmax/4096)
If there are other daemons on the box that need to use shared memory,
then add their likely requirements to shmall too!
cheers
Mark
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To: pgsql-performance@postgresql.org
Cc: markir@paradise.net.nz, cosimo@streppone.it
Subject: Re: postgresql-8.0.1 performance tuning
In-Reply-To: <429D6242.6000804@paradise.net.nz>
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