Re: Can't get Dell PE T420 (Perc H710) perform better than a MacMini with PostgreSQL

On Thu, Apr 2, 2015 at 9:23 AM, Pietro Pugni <pietro(dot)pugni(at)gmail(dot)com> wrote:

> the command
> dmesg | grep -i numa
> doesn’t display me anything. I think T420 hasn’t NUMA on it. Is there a
> way to enable it from Ubuntu? I don’t have immediate access to BIOS (server
> is in another location).
>

NUMA stands for "Non-Uniform-Memory-Access" . It's basically the "label"
for systems which have memory attached to different cpu sockets, such that
accessing all of the memory from a paritciular cpu thread has different
costs based on where the actual memory is located (i.e. on some other
socket, or the local socket).

> For QPI I don’t know what to do. Please, can you give me more details?
>

QPI is the the intel "QuickPath Interconnect". It's the communication path
between CPU sockets. Memory ready by one cpu thread that has to come from
another cpu socket's memory controller goes through QPI.

Google has lots of info on these, and how they impact performance, etc.

> If you want to see how bad the NUMA/QPI is, play with stream to benchmark
> memory performance.
>
>
> With stream you refer to this:
> https://sites.utexas.edu/jdm4372/tag/stream-benchmark/ ? Do you suggest
> me some way to do this kind of tests?
>

Ya, that's the one. I don't have specific tests in mind.

A more simple "overview" might be "numactl --hardware"

a.