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

Andrew Bainbridge andbain at microsoft.com
Wed May 8 11:26:07 CEST 2019


testpmd calls rte_eth_tx_burst() in a loop. Does it fail? I suspect not. If not, then you can gradually transform testpmd until it looks like your code that fails. The loop in question is in txonly.c.

You need a command line something like this for the test:
testpmd -- --forward-mode=txonly --stats-period 1

-----Original Message-----
From: users <users-bounces at dpdk.org> On Behalf Of Arvind Narayanan
Sent: 05 May 2019 00:07
To: Yongseok Koh <yskoh at mellanox.com>
Cc: users <users at dpdk.org>
Subject: Re: [dpdk-users] Issue with mlx5_rxtx.c while calling rte_eth_tx_burst() in DPDK 18.11

It passes __rte_mbuf_sanity_check. rte_mbuf_check() is not available in dpdk 18.02.
I debugged when the assertion failed and double checked all the mbuf's pkt_len and data_len. All seems fine.
Yes, in my case its simple, all mbufs are single segment.

Is there some bound on the number of tx calls we can do consecutively using
mlx5 driver?
Its like if I do a lot of tx calls consecutively (e.g. ~10 to 20 calls to
rte_eth_tx_burst() with each call sending out a burst of ~64 mbufs), I face this problem otherwise I don't.

Thoughts?

Arvind

On Tue, Apr 23, 2019 at 6:45 PM Yongseok Koh <yskoh at mellanox.com> wrote:

>
> > On Apr 21, 2019, at 9:59 PM, Arvind Narayanan 
> > <webguru2688 at 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


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