Re: Limited performance on multi core server

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?

Matthew

Sven Geisler wrote:
> Hi Matthew,
>
> 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 can you provide my patch for Pg 8.0 which should be adaptable for Pg
> 7.4 if you can compile PostgreSQL.
>
> But if you can upgrade you should upgrade to Pg 8.2.5 64-bit. The scale
> up for your concurrent queries will be great.
>
> Sven.
>
> Matthew Lunnon schrieb:
>
>> Hi,
>>
>> 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
>> sure). When the server gets under load from database connections
>> executing reads, lets say 20 - 40 concurrent reads, the CPU's seem to
>> limit at about 30-35% usage with no iowait reported. If I run a simple
>> select at this time it takes 5 seconds, the same query runs in 300
>> millis when the server is not under load so it seems that the database
>> is not performing well even though there is plenty of spare CPU. There
>> does not appear to be large amounts of disk IO and my database is about
>> 5.5G so this should fit comfortably in RAM.
>>
>> changes to postgresql.sql:
>>
>> max_connections = 500
>> shared_buffers = 96000
>> sort_mem = 10240
>> effective_cache_size = 1000000
>>
>> Does anyone have any ideas what my bottle neck might be and what I can
>> do about it?
>>
>> Thanks for any help.
>>
>> Matthew.
>>
>> ---------------------------(end of broadcast)---------------------------
>> TIP 6: explain analyze is your friend
>>
>
>

--
Matthew Lunnon
Technical Consultant
RWA Ltd.

mlunnon(at)rwa-net(dot)co(dot)uk
Tel: +44 (0)29 2081 5056
www.rwa-net.co.uk
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