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    SubjectRe: [discuss] Re: [patch 1/3] x86_64: Node local PDA -- early cpu_to_node
    On Sat, Dec 03, 2005 at 12:02:06AM +0100, Andi Kleen wrote:
    > On Fri, Dec 02, 2005 at 02:51:56PM -0800, Ravikiran G Thirumalai wrote:
    > > On Fri, Dec 02, 2005 at 12:43:49PM +0100, Andi Kleen wrote:
    > > > And are you sure it will work with k8topology.c. Doesn't look like
    > > > that to me.
    > >
    > > I don't have a K8 box yet :(, so I cannot confirm either ways.
    > > But I thought newer opterons need to use ACPI_NUMA instead...
    >
    > k8topology still needs to work - e.g. for LinuxBios and users which use
    > acpi=off and as a fallback for broken SRAT tables. You can't break it right now.
    >

    I don't think this breaks K8 per-se, because x86_cpu_to_apicid[] is setup if
    acpi is compiled in and k8topology sets up apicid_to_node[] at
    k8_scan_nodes. That said, I don't know for sure as I don't have a K8 yet. If
    someone can test this patch on a opteron, compiled with
    ACPI_NUMA as well as K8, (but which falls back to K8 at boot),
    it will be helpful.

    > >
    > > Even if K8 detection is used, cpu_pda will have memory allocated from node0
    > > which is not different from the current state. So this patch helps Opterons
    > > and EM64t boxes which use ACPI_NUMA, right? Also the newer opteron boxes
    > > and em64t NUMA boxes can now get node local memory for static per-cpu areas.
    >
    > Hmm good point. However i would prefer if there was no performance regression
    > between the two options. However i guess it can be kept like this now.
    > Just make sure to comment it well.

    Sure.

    Thanks,
    Kiran
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