On Tue, 13 Dec 2016 14:43:41 +0530
Prem Chaitanya <[email protected]> wrote:
> Hi All,
>
> We modified the l3fwd application to run in interrupt+poll mode. The driver
> we used was IGB with Intel I350 NIC.
> When we ran with 1 lcore and 1 queue, there were no issues. When we tried
> to run with 2 lcores and 2 Rx-queues we are not getting interrupts.
> In one of the documentation(DPDK-201.pdf), it was mentioned that IGB driver
> doesn't support interrupt mode with multiple lcores since it supports only
> 1 epoll-fd.
> Can you please confirm if this is the case?
igb_uio device driver can not support an interrupt per queue (MSI).
> Then we went ahead and loaded the VFIO driver and tried to run the same
> application.
> Now we get an interrupt once and after that when we go back to waiting on
> epoll, we dont receive any further interrupts.
> But when we print the stats for rx-packets we see that there are packets
> waiting in the NIC Rx queue.
> Same behavior is observed even when we run application with 1 lcore and 1
> Rx queue.
You need to do some careful coding to handle interrupt+poll mode.
Look at l3fwd-power example, and even that isn't enough.
Basically, you need to dynamically go in and out of interrupt mode
and use the rx_queue_count function to check for races.
The application must have poll loop like:
while() {
rte_epoll_wait()
if (rx_event) {
readmore:
rte_eth_dev_rx_intr_disable()
while ( (n = rte_eth_rx_queue_burst()) > 0) {
process n packets;
}
rte_eth_dev_rx_intr_enable();
if (rte_eth_dev_rx_queue_count() > 0) {
// lost race
goto readmore;
}
}
}
