Re: [Qemu-devel] Re: [PATCH 0/4] pci: interrupt status/interrupt disable support

[Paul Brook]

> No, this would slow us down because these are per-pin.
> We need a sum of interrupts so that config space
> can be updated by a single command.
> Interrupts are a fastpath, extra loops there should be avoided.

It's really not that much of a fast path. Unless you're doing something 
particularly obscure then even under heavy load you're unlikely to exceed a 
few kHz.  Compared to the average PIC implementation, and the overhead of the 
actual CPU interrupt, I find it hard to believe that looping over precisely 4 
entries has any real performance hit.

Paul