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    SubjectRe: is irq smp affinity good for anything?
    On Tue, Mar 11, 2003 at 08:48:59PM -0500, Mark Hahn wrote:
    > > I did not expect to increase global latency to these results...
    > > and neither to increase latency in the CPU that's receiving
    > > just one interrupt!
    > but isn't that just a cache effect? that is, you're keeping
    > all cpus busy (caches too) with user-space, so when the interrupt
    > comes in, a bound interrupt has no choice, even if the cache
    > is busy with userspace.

    first of all thanks for your reply,

    I think that user space code always has to make the best use of cache as it
    can... in other words, i don't want to use a cpu exclusively for a device
    that delivers 6000 ints/second

    I bound an irq to a cpu because I thought that:

    as spin_irq_locks just disables interrupts locally I should get better
    latency that just one ISR on that particular cpu could at least reduce
    a little the number of times that interrupts get disabled on that cpu

    ... that was my reasoning...

    but latency gets worse... that's not comphrensible for me...


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