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    SubjectRe: IRQ handling difference between i386 and x86_64


    On Sat, 30 Jun 2007, Arjan van de Ven wrote:

    > On Sat, 2007-06-30 at 16:55 +0200, Krzysztof Oledzki wrote:
    >> Hello,
    >>
    >> It seems that IRQ handling is somehow different between i386 and x86_64.
    >>
    >> In my Dell PowerEdge 1950 is it possible to enable interrupts spreading
    >> over all CPUs. This a single CPU, four CORE system (Quad-Core E5335 Xeon)
    >> so I think that interrupts migration may be useful. Unfortunately, it
    >> works only with 32-bit kernel. Booting it with x86_64 leads to situation,
    >> when all interrupts goes only to the first cpu matching a smp_affinity
    >> mask.
    >
    > arguably that is the most efficient behavior... round robin of
    > interrupts is the worst possible case in terms of performance

    Even on dual/quadro core CPUs with shared cache? So why it is possible to
    enable such behaviuor in BIOS, which works only on i386 BTW. :(

    > are you using irqbalance ? (www.irqbalance.org)

    Yes, I'm aware about this useful tool, but in some situations (routing
    for example) it cannot help much as it keeps three cpus idle. :(

    Best regards,

    Krzysztof Olędzki
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