[dpdk-users] RX of multi-segment jumbo frames

Filip Janiszewski contact at filipjaniszewski.com
Sat Feb 9 16:27:24 CET 2019

Il 09/02/19 14:51, Wiles, Keith ha scritto:
>> On Feb 9, 2019, at 5:11 AM, Filip Janiszewski <contact at filipjaniszewski.com> wrote:
>> Hi,
>> I'm attempting to receive jumbo frames (~9000 bytes) on a Mellonox card
>> using DPDK, I've configured the DEV_RX_OFFLOAD_JUMBO_FRAME offload for
>> rte_eth_conf and rte_eth_rxconf (per RX Queue), but I can capture jumbo
>> frames only if the mbuf is large enough to contain the whole packet, is
>> there a way to enable DPDK to chain the incoming data in mbufs smaller
>> than the actual packet?
>> We don't have many of those big packets coming in, so would be optimal
>> to leave the mbuf size to RTE_MBUF_DEFAULT_BUF_SIZE and then configure
>> the RX device to chain those bufs for larger packets, but can't find a
>> way to do it, any suggestion?
> the best i understand is the nic or pmd needs to be configured to split up packets between mbufs in the rx ring. i look in the docs for the nic and see if it supports splitting up packets or ask the maintainer from the maintainers file.

I can capture jumbo packets with Wireshark on the same card (same port,
same setup), which let me think the problem is purely on my DPDK card

According to ethtools, the jumbo packet (from now on JF, Jumbo Frame) is
detected at phy level, the couters rx_packets_phy, rx_bytes_phy,
rx_8192_to_10239_bytes_phy are properly increased.

There was an option to setup manually the support for JF but was remove
from DPDK after version 16.07: CONFIG_RTE_LIBRTE_MLX5_SGE_WR_N.
According to the release note:

Improved jumbo frames support, by dynamically setting RX scatter gather
elements according to the MTU and mbuf size, no need for compilation
parameter ``MLX5_PMD_SGE_WR_N``

Not quire sure where to look for..

>> Thanks
>> -- 
>> BR, Filip
>> +48 666 369 823
> Regards,
> Keith

BR, Filip
+48 666 369 823

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