[dpdk-dev] Questions about TX descriptors run out occasionally

[Hui Liu <huiliu0213@gmail.com>]

Hi Experts,

I'm developing my own dpdk-based application via Intel 82599ES port. My
Application is doing a job to send ICMP requests (packet size varies from
64 bytes to 1472 bytes, 200,000 pps, 1.1Gbps) and receive responses, with
ARP request/response and ICMP response handling when necessary. It was
working pretty fine in 5 hours to 10 days  randomly and then TX descriptors
run out and cannot be freed by ixgbe_tx_free_bufs() due to DD bit is not
set:

        /* check DD bit on threshold descriptor */
        status = txq->tx_ring[txq->tx_next_dd].wb.status;
        if (!(status & IXGBE_ADVTXD_STAT_DD))
                return 0;

My tx queue setup is:
        tx_conf->tx_thresh.pthresh = 64;
        tx_conf->tx_thresh.hthresh = 0;
        tx_conf->tx_thresh.wthresh = 0;
        tx_conf->tx_free_thresh = 256;
        tx_conf->tx_rs_thresh = 32;
        tx_conf->txq_flags = ETH_TXQ_FLAGS_NOMULTSEGS |
ETH_TXQ_FLAGS_NOOFFLOADS;


I tried to read code to see if there is any case to take these descriptors
and never set IXGBE_ADVTXD_STAT_DD back but no luck yet. And I have not
even found the related code when IXGBE_ADVTXD_STAT_DD is set/unset when
descriptor is taken/released other than reset queues... So may I ask:
1. where do we set/unset IXGBE_ADVTXD_STAT_DD when descriptor is
taken/released?
2. any suggestion or information I should focus on to debug this issue? Is
this typically because of my upper application not alloc/free correctly or
any other problem?
3. another friend in dpdk-user list raised same issue in fm10k driver, but
later he mentioned his problem was because of overheating of NIC
(temperature was close to 85 degree Celsius). After setting system FAN to
full speed, he made it work perfectly. Since in my system I don't have
fan/temp sensors so I could not check this. Might this problem be caused by
high temperature in case?

Regards,
Hui