Hi Stephen, Thanks a lot for your response. We wrote our application(by modifying l3fwd application) and by looking at the l3fwd-power sample application. But didnt know about this race you are talking about. Question: If we enable interrupt and go into epoll_wait, wont the interrupts be pending in eventfd ? Or am i missing something.
I applied the queue_count check and tried to read again in case there are packets. But still i see there is a lot of inconsistency in receiving interrupts. After i did this change, first time i ran the application i saw interrupts coming in, but from subsequent time i don't see them anymore. Here is the our code flow. 1. Register for interrupts 2. Poll Rx-Queue. 3. If idle_poll crosses configured limit, turn-on interrupt for that queue and goto epoll_wait 4. One interrupt is received then disable interrupt for that queue and poll. Let me know if you need any specific information. On Wed, Dec 14, 2016 at 3:52 AM, Stephen Hemminger < [email protected]> wrote: > 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; > } > } > } > -- Regards Prem
