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    SubjectRe: questions on NAPI processing latency and dropped network packets
    Rick Jones wrote:
    >> 1) Interrupts are being processed on both cpus:
    >> root@base0-0-0-13-0-11-1:/root> cat /proc/interrupts
    >> CPU0 CPU1
    >> 30: 1703756 4530785 U3-MPIC Level eth0
    > IIRC none of the e1000 driven cards are multi-queue

    the pci-express variants are, but the functionality is almost always disabled (and
    relatively new anyway).

    even with multiqueue, you can still have only a single irq line (which defeats the
    purpose of course mostly).

    >, so while the above
    > shows that interrupts from eth0 have been processed on both CPUs at
    > various points in the past, it doesn't necessarily mean that they are
    > being processed on both CPUs at the same time right?

    never will, an irq can only be processed on one cpu at a time anyway, obviously
    the irq here has been migrated ONCE from one of the cpu's to the other.
    unfortunately you can't see from /proc/interrupts whether this happens frequently
    or not, or how many times it happened before.


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      Last update: 2008-01-10 20:05    [W:0.029 / U:13.828 seconds]
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