[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Spurious "NUMA placement failed, performance might be affected" message on ARM
On lun, 2014-04-28 at 11:01 +0100, Ian Campbell wrote: > On Mon, 2014-04-28 at 11:55 +0200, Dario Faggioli wrote: > > While I wonder why that does not happen on ARM, a sensible solution > > would be to bail earlier, if we find only one NUMA node exist, for > > whatever arch. Would that be ok? If yes, I can arrange a patch pretty > > easily, I think. > > I suppose if ARM is also reporting 1 node then for some reason this > check isn't hitting and moving it earlier won't help (not that it would > be a bad idea independently to optimise this a bit). > Exactly. Honestly, I thought it was like that already, but I was evidently mis-remembering. I'll do that as soon as we will have sorted this out. > Perhaps ARM is reporting no NUMA nodes? The xl info -n output suggests > not but where else should I check. > The output (which I removed) really looks similar to my non-NUMA x86 box. As per what to check, in libxl__get_numa_candidate(), if it enters this loop (and it should): for (comb_ok = comb_init(gc, &comb_iter, nr_suit_nodes, min_nodes); comb_ok; comb_ok = comb_next(comb_iter, nr_suit_nodes, min_nodes)) { The only reason why it does not get to the end of the first iter (and set cndt_found to 1) seems to be one of these if-s: /* If there is not enough memory in this combination, skip it * and go generating the next one... */ nodes_free_memkb = nodemap_to_free_memkb(ninfo, &nodemap); if (min_free_memkb && nodes_free_memkb < min_free_memkb) continue; /* And the same applies if this combination is short in cpus */ nodes_cpus = nodemap_to_nr_cpus(tinfo, nr_cpus, suitable_cpumap, &nodemap); if (min_cpus && nodes_cpus < min_cpus) continue; With only 1 node, the first one should really be false, or we shouldn't be here. The second is, I think, possible, but very unlikely (does your guest have more vCPUs than the host has pCPUs?). I'd be happy to have a look myself, but I don't have an ARM (cross) build environment ready right now... Perhaps this is the chance to get one, though... Do you want me to? (provided I can access that or a similar box) Regards, Dario -- <<This happens because I choose it to happen!>> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) Attachment:
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