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    SubjectRe: [rfc 08/45] cpu alloc: x86 support
    Date
    On Tuesday 20 November 2007 13:02, 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%?)

    Small socket count systems are going to increasingly be NUMA in future.
    If CONFIG_NUMA hurts performance by that much on those systems, then the
    kernel is broken IMO.
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