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

Arvind Narayanan webguru2688 at gmail.com
Wed May 8 15:03:50 CEST 2019


I will try using testpmd, and get back. Thanks.
Since my packets are single segment, as Yongseok suggested - I tried
commenting out the asserts. By doing this, the tx descriptors would get
depleted and would halt all tx completely. But if packets are sent slowly
by reducing traffic-generator's transmission speed, there is no problem.

What does "vectorized TX bursts" mean? Does executing consecutive tx_burst
calls (where each call is sending out ~64 mbufs) qualify as vectorized tx
burst?
I tried finding information about this online, but couldn't find anything
useful. I see a bunch of runtime config params for vectorized tx in mlx5.

Arvind


On Wed, May 8, 2019 at 4:26 AM Andrew Bainbridge <andbain at microsoft.com>
wrote:

> 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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