Re: Can I use rte_pktmbuf_chain to chain multiple mbuffs for calling only single tx_eth_burst API

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 9 Feb 2022 22:18:24 +0000
Ferruh Yigit <ferruh.yigit@intel.com> wrote:

> On 2/9/2022 6:03 PM, Ansar Kannankattil wrote:
> > Hi
> > My intention is to decrease the number of rte_tx_eth_burst calls, I know that mentioning nb_pkts will result in sending multiple packets in a single call.
> > But providing nb_pkts=1 and posting a head mbuff having number of mbuffs linked with it will results sending multiple packets  
> 
> If driver supports, you can do it.
> Driver should expose this capability via RTE_ETH_TX_OFFLOAD_MULTI_SEGS flag,
> in 'dev_info->tx_offload_capa'.
> 
> > If not, what is the use case of linking multiple mbuffs together  
> 
> It is also used in Rx path (again if driver supports).

I think Ansar was asking about chaining multiple packets in one call to tx burst.
The chaining in DPDK is to make a single packet out of multiple pieces (like writev).

DPDK mbufs were based on original BSD concept.
In BSD mbufs, mbuf has two linked lists.
  BSD m->m_next pointer == DPDK m->next  for multiple parts of packet.
  BSD m->m_nextpkt                       for next packet in queue

There is no nextpkt in DPDK.