Using interrupts with DPDK - dpdk

Question

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 igb_uio and ixgbe drivers 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 since this is supposed to be easy to do. I based my code closely on the l3fwd-power example.

Answer 1

I talked with Dmitry Kozlyuk who pointed out that the ixgbe driver requires interrupts to be re-armed before each call to rte_epoll_wait. So rte_eth_dev_rx_intr_enable should be called before each call to rte_epoll_wait in the while loop:
rte_epoll_event event;
while (true) {
CHECK_EQ(rte_eth_dev_rx_intr_enable(kPort, kQueue), 0);
int n = rte_epoll_wait(RTE_EPOLL_PER_THREAD, &event, /*maxevents=*/1,
/*timeout=*/1000);
if (n == 0) {
// Timeout expired.
} else {
// Received RX interrupt.
}
}
You need to do the re-arm before each call to rte_poll_wait for some other drivers, too, such as vmxnet3.