Re: [dpdk-users] Issue with mlx5_rxtx.c while calling rte_eth_tx_burst() in DPDK 18.11

[Yongseok Koh <yskoh@mellanox.com>]

> On Apr 21, 2019, at 9:59 PM, Arvind Narayanan <webguru2688@gmail.com> wrote:
> 
> I am running into a weird problem when using rte_eth_tx_burst() using mlx5
> in dpdk 18.11, running on Ubuntu 18.04 LTS (using Mellanox Connect X5 100G
> EN).
> 
> Here is a simplified snippet.
> 
> ==================
> #define MAX_BATCHES 64
> #define MAX_BURST_SIZE 64
> 
> struct batch {
>    struct rte_mbuf *mbufs[MAX_BURST_SIZE]; // array of packets
>    int num_mbufs; // num of mbufs
>    int queue; // outgoing tx_queue
>    int port; // outgoing port
> }
> 
> struct batch * batches[MAX_BATCHES];
> 
> /* dequeue a number of batches */
> int batch_count = rte_ring_sc_dequeue_bulk(some_rte_ring, (void **)
> &(batches), MAX_BATCHES, NULL);
> 
> /* transmit out all pkts from every batch */
> if (likely(batch_count > 0)) {
>    for (i = 0; i < batch_count; i++) {
>        ret = rte_eth_tx_burst(batches[i]->port, batches[i]->queue, (struct
> rte_mbuf **) batches[i]->mbufs,
>                               batches[i]->num_mbufs);
>    }
> }
> 
> ==================
> 
> At rte_eth_tx_burst(), I keep getting an error saying:
> myapp: /home/arvind/dpdk/drivers/net/mlx5/mlx5_rxtx.c:1652: uint16_t
> txq_burst_empw(struct mlx5_txq_data *, struct rte_mbuf **, uint16_t):
> Assertion `length == DATA_LEN(buf)' failed.
> OR
> myapp: /home/arvind/dpdk/drivers/net/mlx5/mlx5_rxtx.c:1609: uint16_t
> txq_burst_empw(struct mlx5_txq_data *, struct rte_mbuf **, uint16_t):
> Assertion `length == DATA_LEN(buf)' failed.
> 
> I have debugged and ensured all the mbuf counts (at least in my code) are
> good. All the memory references to the mbufs also look good. However, I am
> not sure why Mellanox driver would complain.
> 
> I have also tried to play with mlx5_rxtx.c by changing above lines to
> something like
> assert(length == pkts_n); // pkts_n is an argument passed to the func.
> Didn't help.
> 
> Any thoughts?

Hi,

Does your mbuf pass rte_mbuf_check()?
That complaint is regarding mismatch between m->pkt_len and m->data_len.
If the mbuf is single segment packet (m->nb_segs == 1, m->next == NULL),
m->pkt_len should be same as m->data_len.

That assert() ins't strictly needed in the txq_burst_empw() though.


Thanks,
Yongseok