Re: hwo to adjust interrupt?

Bryan Henderson
2005-08-12T17:35:32Z

>>How much extra work does Linux have to do for each interrupt?
>
>usually 1 pci mmio read; the rest is negligible.

I was hoping you would cater better to my ignorance of how PCI interrupt
handling works in Linux.

Is it the case that Linux invokes the registered interrupt handler of each
of the drivers for the devices that share the interrupt, and each does an
mmio read of its device to find out if it had reason to generate an
interrupt? So the waste is that extra call, and you're saying the CPU
instructions involved are negligible compared to the mmio read?

Are these level-sensitive interrupts, so that if both devices need service
at the same time, they generate just one interrupt and neither device
driver call is wasted?