Messages in this thread |  | | Date | Wed, 3 Oct 2001 10:38:34 +0200 (CEST) | From | Ingo Molnar <> | Subject | Re: [announce] [patch] limiting IRQ load, irq-rewrite-2.4.11-B5 |
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On Tue, 2 Oct 2001, jamal wrote:
> You are still missing the point (by humping on the literal meaning of > the example i provide), the point is: fine grained vs shutting down > the whole IRQ.
i'm convinced that this is a minor detail.
there are *tons* of disadvantages if IRQs are shared. In any high-performance environment, not having enough interrupt sources is a sizing or hw design mistake. You can have up to 200 interrupts even on a PC, using multipe IO-APICs. Any decent server board distributes interrupt sources properly. Shared interrupts are a legacy of the PC design, and we are moving away from it slowly but surely. Especially under gigabit loads there are several PCI busses anyway, so getting non-shared interrupts is not only easy but a necessity as well. There is no law in physics that somehow mandates or prefers the sharing of interrupt vectors: devices are distinct, they use up distinct slots in the board. The PCI bus can get multiple IRQ sources out of a single card, so even multi-controller cards are covered.
i fully agree that both the irq code and drivers themselves have to handle shared interrupts correctly, and we should not penalize shared interrupts unnecesserily, but do they have to influence our design decisions too much? Nope.
Ingo
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