Re: [announce] [patch] limiting IRQ load, irq-rewrite-2.4.11-B5

Ingo Molnar
2001-10-04T10:27:23Z

On Thu, 4 Oct 2001, BALBIR SINGH wrote:

> Shouldn't the interrupt mitigation be on a per CPU basis? [...]

this was done by an earlier version of the patch, but it's wrong. An IRQ
cannot arrive to multiple CPUs at once (well, normal device interrupts at
least) - it will arrive either to some random CPU, or can be bound via
/proc/irq/N/smp_affinity. (there are architectures that do
soft-distribution of interrupts, but that can be considered pseudo-random)

But in both cases, it's the actual, per-irq IRQ load that matters. If one
CPU is hogged by IRQ handlers that is not an issue - other CPUs can still
take over the work. If *all* CPUs are hogged then the patch detects the
overload.

Ingo