Re: RFC: IRQ affinity (aka interrupt routing)

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Mon, Jul 28, 2014 at 12:20:07PM +0900, Kengo NAKAHARA wrote:
> 
> I think analyzing interrupt rates, deciding which IRQ's interrupts
> shuld be moved and deciding which CPU is assigned the moved interrupts
> are complex.

I think this may prove counterproductive.  For one reason, it may cause
harmful cache behavior as the datastructures associated with the same
network flow move from one CPU to another as packets are received on
different interfaces for the transmit and receive directions.

I think you really don't want to do anything that could impede the use
of hardware classifiers to put the packets for the same flow on the
same CPUs' queues -- and balancing interrupts in userspace rather than in
the kernel seems to me likely to do just that.

Thor