Re: [dpdk-dev] Question about jumbo frame support on ixgbe

["Zhao1, Wei" <wei.zhao1@intel.com>]

Add Stephen Hemminger <stephen@networkplumber.org> for discussion.

> -----Original Message-----
> From: Zhao1, Wei
> Sent: Thursday, November 1, 2018 11:10 AM
> To: 'Hideyuki Yamashita' <yamashita.hideyuki@po.ntt-tx.co.jp>;
> dev@dpdk.org
> Subject: RE: [dpdk-dev] Question about jumbo frame support on ixgbe
> 
> Hi,  Hideyuki Yamashita
> 
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Hideyuki
> > Yamashita
> > Sent: Wednesday, October 31, 2018 4:22 PM
> > To: dev@dpdk.org
> > Subject: [dpdk-dev] Question about jumbo frame support on ixgbe
> >
> > Hi,
> >
> > I have a very basic question about jumbo frame support for ixgbe.
> >
> > I understand that some drivers support jumbo frame and if it receive
> > jumbo packet (greater than 1500 byte), it creates mbuf chains and pass
> > it to DPDK application through e.g. rte_eth_rx_burst.
> >
> > However it looks that ixgbe driver does not support jumbo frame.
> >
> > Q1. Is my understanding above correct?
> > Q2. If A1 equals YES, then are there any future plan to support jumbo
> > frame on ixgbe?
> 
> Your understanding above correct, but 82599 and x550 has support jumbo
> frame receive by now!
> In order to use this feature on ixgbe, you need do the following steps:
> 
> 1. you must set dev_conf.rxmode. max_rx_pkt_len to a big number, eg. 9500,
> when doing port start, for example when start port in API
> rte_eth_dev_start().
> ixgbe_dev_rx_init() will chose a scatter receive function if the
> max_rx_pkt_len is larger than the mbuf size, you do not need to set
> DEV_RX_OFFLOAD_SCATTER bit in dev_conf.rxmode.offloads, this is the
> work of PMD driver when it detect jumbo frame is needed to be supported.
> 
> 2. set dev_conf.txmode.offloads bit of  DEV_TX_OFFLOAD_MULTI_SEGS to 1
> when doing rte_eth_tx_queue_setup() or , this is very important!!
> If you not do this, you may only receive JUMBO frame but not forward out.
> Because as you say, the receive packets maybe has a mbuf chains(depending
> on the size relationship of mbuf size and the max_rx_pkt_len).
> But in ixgbe PMD for setting tx function, it is confusing  in
> ixgbe_set_tx_function(), you need  to take care of it, it is based on queue
> offloads bit!
> 
> 3. enable it using CLI "port config mtu <port_id> <value>" if you are using
> testpmd or using API rte_eth_dev_set_mtu() for your own APP.
> The mtu number is just what you need to update for a large number.
> 
> And all my discussion is based on pf port, if you are using vf, we can have a
> further discussion.
> Please feel free to contact me if necessary.
> 
> >
> > BR,
> > Hideyuki Yamashita
> > NTT TechnoCross