Re: Performance problems on 4/8way Opteron (dualcore) HP

Hi Jeff,

which box are you running precisely and which OS/kernel?

We need to run 32bit because we need failover to 32 bit XEON system
(DL580). If this does not work out we probably need to switch to 64 bit
(dump/restore) and run a nother 64bit failover box too.

Regards,

Dirk



Jeffrey W. Baker wrote:
> On Fri, 2005-07-29 at 10:46 -0700, Josh Berkus wrote:
>
>>Dirk,
>>
>>
>>>does anybody have expierence with this machine (4x 875 dual core Opteron
>>>CPUs)?
>
>
> I'm using dual 275s without problems.
>
>
>>Nope.   I suspect that you may be the first person to report in on
>>dual-cores.  There may be special compile issues with dual-cores that
>>we've not yet encountered.
>
>
> Doubtful.  However you could see improvements using recent Linux kernel
> code.  There have been some patches for optimizing scheduling and memory
> allocations.
>
> However, if you are running this machine in 32-bit mode, why did you
> bother paying $14,000 for your CPUs?  You will get FAR better
> performance in 64-bit mode.  64-bit mode will give you 30-50% better
> performance on PostgreSQL loads, in my experience.  Also, if I remember
> correctly, the 32-bit x86 kernel doesn't understand Opteron NUMA
> topology, so you may be seeing poor memory allocation decisions.
>
> -jwb
>
>
>>>We run RHEL 3.0, 32bit and under high load it is a drag. We
>>>mostly run memory demanding queries. Context switches are pretty much
>>>around 20.000 on the average, no cs spikes when we run many processes in
>>>parallel. Actually we only see two processes in running state! When
>>>there are only a few processes running context switches go much higher.
>>>At the moment we are much slower that with a 4way XEON box (DL580).
>>
>>Um, that was a bit incoherent.  Are you seeing a CS storm or aren't you?
>>