Messages in this thread | | | Date | Mon, 19 Nov 2007 18:18:42 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [rfc 08/45] cpu alloc: x86 support |
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Christoph Lameter wrote: > On Mon, 19 Nov 2007, H. Peter Anvin wrote: > >> You're making the assumption here that NUMA = large number of CPUs. This >> assumption is flat-out wrong. > > Well maybe. Usually one gets to NUMA because the hardware gets too big to > be handleed the UMA way. > >> On x86-64, most two-socket systems are still NUMA, and I would expect that >> most distro kernels probably compile in NUMA. However, >> burning megabytes of memory on a two-socket dual-core system when we're >> talking about tens of kilobytes used would be more than a wee bit insane. > > Yeah yea but the latencies are minimal making the NUMA logic too expensive > for most loads ... If you put a NUMA kernel onto those then performance > drops (I think someone measures 15-30%?) >
How do you handle this memory, in the first place? Do you allocate the whole 2 MB for the particular CPU, or do you reclaim the upper part of the large page? (I haven't dug far enough into the source to tell.)
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