Re: [gentoo-user] Dual or Quad CPU complications?

[Michael Mol]

Something _really_ weird happened to your quoting; you quoted my
email, but your email client said you wrote it.

On Mon, Dec 17, 2012 at 2:00 AM, J. Roeleveld <joost@××××××××.org> wrote:
>> On Sun, Dec 16, 2012 at 10:39 AM, J. Roeleveld <joost@××××××××.org> wrote:

^-- weird --^

>>> On Sunday, December 16, 2012 01:52:46 PM Volker Armin Hemmann wrote:
>>>> Am Samstag, 15. Dezember 2012, 20:57:24 schrieb J. Roeleveld:
>>>> > Even on a system with only 2 sockets, it can be useful to have NUMA
>>>> > available.
>>>>
>>>> or not, because it costs you performance.
>>>
>>> When does it cost performance?
>>> In all situations?
>>
>> It adds some additional logic to memory allocation (put an allocation
>> near the process that uses it) and to process scheduling (keep the
>> process near its memory, but bump it to a more distant idle core if
>> necessary).
>
> That's the way it's supposed to work, yes :)
>
>> In all honestly, it's not a performance loss you're likely to notice,
>> unless you're so in need of squeezing out every spare cycle that you
>> most definitely _have_ hardware where there are disconnected memory
>> banks. I'm not convinced it's even measurable for us mundanes and our
>> hardware.
>
> I don't think I would notice it either, but as the system I have supports
> it, I want to use it.
> And then I want to be certain it actually supports it correctly.
>
> The system I'm talking about is used for testing purposes. Running
> multiple VMs. As far as I know, Xen has support for it, just need to
> configure it properly.
> And for this usecase, I think NUMA with only 2 physical CPUs should make a
> positive difference.

Don't get me wrong; I was arguing that it shouldn't hurt to have it enabled. :)

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:wq