> On Sun, Dec 16, 2012 at 10:39 AM, J. Roeleveld <jo...@antarean.org> wrote: >> 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. -- Joost
