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Re: Limited performance on multi core server

From: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>
To: mlunnon(at)rwa-net(dot)co(dot)uk
Cc: Sven Geisler <sgeisler(at)aeccom(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Limited performance on multi core server
Date: 2007-12-12 15:47:00
Message-ID: 47600274.40009@commandprompt.com (view raw or flat)
Thread:
Lists: pgsql-performance
Matthew Lunnon wrote:
> Hi Sven,
> 
> Does this mean that one option I have is to use a multi core Intel based 
> server instead of an AMD based server?

Wow... hold on.

>> I remember that I also an issue with AMD Opterons before Pg 8.1
>> There is a specific Opteron behaviour on shared memory locks which adds
>> a extra "penalty" during the execution time for Pg code before 8.1.

I would like to see some proof of this.


>> I can you provide my patch for Pg 8.0 which should be adaptable for Pg
>> 7.4 if you can compile PostgreSQL.
>>

The real answer here is to upgrade to 8.1.10 or 8.2.5. 64bit if you can.

>>> I have a 4 * dual core 64bit AMD OPTERON server with 16G of RAM, running
>>> postgres 7.4.3.  This has been recompiled on the server for 64 stored
>>> procedure parameters, (I assume this makes postgres 64 bit but are not

This type of machine, assuming you have decent IO available will 
generally be very fast with anything >= 8.1.

>>> changes to postgresql.sql:
>>>
>>> max_connections = 500
>>> shared_buffers = 96000

Way to high for 7.4. Way to low for 8.1 or above (based on what you 
mention your work load is)

>>> sort_mem = 10240

Based on your specs this actually may be fine but I would suggest 
reviewing it after you upgrade.

>>> effective_cache_size = 1000000
>>>

Again, too low for 8.1 or above.

Sincerely,

Joshua D. Drake

--
The PostgreSQL Company: http://www.commandprompt.com/


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