The mbuf pool said be configured to be the size of the largest packet you expect to receive. If you're getting packets longer than that, I would expect you to see problems. Same goes for transmitting; I believe it will just read past the end of the mbuf data.
On Sun, Jun 7, 2020, 06:36 Alex Kiselev <[email protected]> wrote: > On 2020-06-07 15:16, Cliff Burdick wrote: > > That shouldn't matter. The mbuf size is allocated when you create the > > mempool, and data_len/pkt_len are just to specify the size of the > > total packet and each segment. The underlying storage size is still > > the same. > > It does matter. I've done some tests and after > sending a few mbufs with data_len/pkt_len bigger than the size > of mbuf's underlying buffer the app stops sending/receiving packets. > The PMD apparently goes beyong the mbuf's buffer, that's why > I sill think that my question about the impact of using incorrect > data_len/pkt is valid. > > > > > Have you checked to see if it's potentially a hugepage issue? > > Please, explain. > > The app had been working two monghts before the crush > and the load was 3-4 gbit/s, so no, I don't think that > something is wrong with hugepages on that machine. > > > > > > On Sun, Jun 7, 2020, 02:59 Alex Kiselev <[email protected]> wrote: > > > >> On 2020-06-07 04:41, Cliff Burdick wrote: > >>> I can't tell from your code, but you assigned nb_rx to the number > >> of > >>> packets received, but then used vec_size, which might be larger. > >> Does > >>> this happen if you use nb_rx in your loops? > >> > >> No, this doesn't happen. > >> I just skip the part of the code that translates nb_rx to vec_size, > >> since that code is double checked. > >> > >> My actual question now is about possible impact of using > >> incorrect values of mbuf's pkt_len and data_len fields. > >> > >>> > >>> On Sat, Jun 6, 2020 at 5:59 AM Alex Kiselev <[email protected]> > >>> wrote: > >>> > >>>>> 1 июня 2020 г., в 19:17, Stephen Hemminger > >>>> <[email protected]> написал(а): > >>>>> > >>>>> On Mon, 01 Jun 2020 15:24:25 +0200 > >>>>> Alex Kiselev <[email protected]> wrote: > >>>>> > >>>>>> Hello, > >>>>>> > >>>>>> I've got a segmentation fault error in my data plane path. > >>>>>> I am pretty sure the code where the segfault happened is ok, > >>>>>> so my guess is that I somehow received a corrupted mbuf. > >>>>>> How could I troubleshoot this? Is there any way? > >>>>>> Is it possible that other threads of the application > >>>>>> corrupted that mbuf? > >>>>>> > >>>>>> I would really appriciate any advice. > >>>>>> Thanks. > >>>>>> > >>>>>> DPDK 18.11.3 > >>>>>> NIC: 82599ES > >>>>>> > >>>>>> Code: > >>>>>> > >>>>>> nb_rx = rte_eth_rx_burst(port_id, queue_id, pkts_burst, > >>>>>> MAX_PKT_BURST); > >>>>>> > >>>>>> ... > >>>>>> > >>>>>> for (i=0; i < vec_size; i++) { > >>>>>> rte_prefetch0(rte_pktmbuf_mtod(m_v[i], void *)); > >>>>>> > >>>>>> for (i=0; i < vec_size; i++) { > >>>>>> m = m_v[i]; > >>>>>> eth_hdr = rte_pktmbuf_mtod(m, struct ether_hdr *); > >>>>>> eth_type = rte_be_to_cpu_16(eth_hdr->ether_type); > >>>> <--- > >>>>>> Segmentation fault > >>>>>> ... > >>>>>> > >>>>>> #0 rte_arch_bswap16 (_x=<error reading variable: Cannot access > >>>> memory > >>>>>> at address 0x4d80000000053010>) > >>>>> > >>>>> Build with as many of the debug options turned on in the DPDK > >>>> config, > >>>>> and build with EXTRA_CFLAGS of -g. > >>>> > >>>> Could using an incorrect (a very big one) value of mbuf pkt_len > >> and > >>>> data_len while transmitting cause mbuf corruption and following > >>>> segmentation fault on rx? >
