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SubjectRe: Improving raw network performance [was Apache performance etc.]
Benjamin Herrenschmidt wrote:
> I beleive he though about using the kernel to mask/unmask the irq line,
> which can cause trouble with shared IRQs. Of course, the solution is to
> mask them on-chip.

Ok, this I understand. Barring interactions with RTLinux, which doesn't
disable them on chip.

> Note that masking/unmasking wiht the kernel's disable_irq/enable_irq from
> within the IRQ handler will not work on some platforms (notably PPC,
> except if things change since the last time I hacked in this piece of
> code). The problem is that if you mask the irq from within the handler,
> it will be unmasked by the kernel when going out of the handler.

I think this is true on x86 also, at least for 8259 irqs.

I'm suggesting a change to the generic interrupt dispatch code rather
than to the drivers, though the drivers might have to inform the
dispatch code that it's ok to switch to timed polling.

-- Jamie

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