Enable RX interrupts

[Dmitry Kozlyuk]

2021-10-31 22:50 (UTC-0700), Jack Humphries:
> Hi folks,
> 
> Hope all are well. I’m trying to enable interrupts in DPDK so that my network receive thread can sleep on an epoll until packets arrive. I am using the ixgbe kernel driver and igb_uio userspace driver with an Intel 82599ES 10Gbps NIC.
> 
> I'm doing roughly the following to enable the interrupts, but the epoll never indicates that packets have arrived. The thread only handles packets when the epoll times out. I don't even see interrupts arrive from the device when monitoring /proc/interrupts.
> 
> port_conf.intr_conf.rxq = 1;
> 
> ...
> 
> CHECK_EQ(rte_eth_dev_rx_intr_ctl_q(kPort, kQueue, RTE_EPOLL_PER_THREAD,
>                                    RTE_INTR_EVENT_ADD, nullptr),
>          0); 
> CHECK_EQ(rte_eth_dev_rx_intr_enable(kPort, kQueue), 0);
> 
> ...
> 
> rte_epoll_event event;
> while (true) {
>   int n = rte_epoll_wait(RTE_EPOLL_PER_THREAD, &event, /*maxevents=*/1,
>                          /*timeout=*/1000);
>   if (n == 0) {
>     // Timeout expired.
>   } else {
>     // Received RX interrupt.
>   }
> }
> 
> Given that I don't see anything coming through in /proc/interrupts, I am going to start digging through the ixgbe driver. However, I wanted to ask here first to see if my setup is missing anything obvious. I based it closely on the l3fwd-power example, though I haven't been able to get that example up and running yet since my NIC only has one port plugged in right now and the example requires two (COVID building restrictions).
> 
> Thanks,
> Jack Humphries

Hi Jack,

Have you called rte_eth_dev_rx_intr_enable(port_id, queue_id)?

Not sure about ixgbe, but vmxnet3 also requires rearming interrupts with it
on each iteration before rte_epoll_wait().
This is what l3fwd-power does by the way (see turn_on_off_intr() function).

+ ixgbe maintainer just in case.