Enable RX interrupts

[Jack Humphries]

Thanks Stephen. I am just using one RX queue from the NIC. I assume that since I don’t need per-queue interrupts here since there is only one queue, I should be good using ixgbe+igb_uio?

Thanks,
Jack

> On Nov 1, 2021, at 8:20 AM, Stephen Hemminger <stephen at networkplumber.org> wrote:
> 
> On Sun, 31 Oct 2021 22:50:40 -0700
> Jack Humphries <jack at chillysky.com> wrote:
> 
>> 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).
> 
> If you are going to use interrupts you need to have MSI-X to get per-queue interrupts.
> The igb_uio driver doesn't support this; you need to use vfio-pci in kernel to get queue interrupts.