Re: PostgreSQL on Dual Processors, Dual-Core AMD Chips

Mark Rae wrote:
> On Wed, Oct 19, 2005 at 12:32:36AM -0700, William Yu wrote:
>
>>Expect to need to upgrade to later Linux cores though. Previous kernel
>>on this server was 2.6.9+ (FC3 64-bit) -- promptly kernel panic'd upon
>>install of the DCs. FC3 installer did the same thing. Went to FC4
>>(2.6.11+) and it has run perfect for the past 3 months. We'll probably
>>do a yum update to 2.6.13+ to take advantage of the better NUMA code now
>>that we've successfully done this update on a less critical server.
>
>
> You should definitely do the upgrade to 2.6.13, the previous
> versions had problems were they would allocate memory to
> the wrong bank of memory when using dual core CPUs. So you
> would find only about a 20% improvement over a single core.
>
> With the newer kernels you should find that a dual core will
> be giving you about 80% increase over a single core.

I'm not experiencing this problem right now because I have NUMA disabled
in the BIOS. :) I'm not sure NUMA will help that much for Postgres due
to Postgres shared memory + OS caching architecture -- but I'll run it
with NUMA on for a week and then compare it to NUMA off after we do the
kernel upgrade. (Ordinarily, I would be afraid to do this type of
testing on a production server but this 2xDC is so freaking fast, I can
afford to give away 80%+ of the processing power and still be within my
performance target.)