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