David Daney <ddaney@xxxxxxxxxxxxxxxxxx> writes: > Chris Friesen wrote: >> On 10/22/2009 03:40 PM, David Daney wrote: >> >>> The main problem I have encountered is how to fit the interrupt >>> management into the kernel framework. Currently the interrupt source >>> is connected to a single irq number. I request_irq, and then manage >>> the masking and unmasking on a per cpu basis by directly manipulating >>> the interrupt controller's affinity/routing registers. This goes >>> behind the back of all the kernel's standard interrupt management >>> routines. I am looking for a better approach. >>> >>> One thing that comes to mind is that I could assign a different >>> interrupt number per cpu to the interrupt signal. So instead of >>> having one irq I would have 32 of them. The driver would then do >>> request_irq for all 32 irqs, and could call enable_irq and disable_irq >>> to enable and disable them. The problem with this is that there isn't >>> really a single packets-ready signal, but instead 16 of them. So If I >>> go this route I would have 16(lines) x 32(cpus) = 512 interrupt >>> numbers just for the networking hardware, which seems a bit excessive. >> >> Does your hardware do flow-based queues? In this model you have >> multiple rx queues and the hardware hashes incoming packets to a single >> queue based on the addresses, ports, etc. This ensures that all the >> packets of a single connection always get processed in the order they >> arrived at the net device. >> > > Indeed, this is exactly what we have. > > >> Typically in this model you have as many interrupts as queues >> (presumably 16 in your case). Each queue is assigned an interrupt and >> that interrupt is affined to a single core. > > Certainly this is one mode of operation that should be supported, but I would > also like to be able to go for raw throughput and have as many cores as possible > reading from a single queue (like I currently have). I believe will detect false packet drops and ask for unnecessary retransmits if you have multiple cores processing a single queue, because you are processing the packets out of order. Eric
