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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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