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    SubjectRe: new IRQ scalability changes in 2.3.48
    On Fri, Mar 03, 2000 at 03:25:23PM +0100, Ingo Molnar wrote:
    > check out the fast path of level-triggered PCI IRQs:
    > do_IRQ()
    > mask_and_ack_level_ioapic_irq: empty!
    > ->handler()
    > end_level_ioapic_irq: a fast local-APIC write
    > no lowlevel spinlock taken. This is actually the case where the IOAPIC IRQ
    > hardware turned out to be very sane. The borken edge-triggered case is
    > nicely isolated.

    I have not looked at the APIC docs recently, but
    doesn't this block irqs during the "fast path" ?

    Since we need a spin lock anyways in doIRQ, I still don't get how
    this makes things any better.

    Victor Yodaiken
    FSMLabs is a servicemark and a service of
    VJY Associates L.L.C, New Mexico.

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