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* Concept clarification on NICS with multiple queues
@ 2021-12-20 18:22 fwefew 4t4tg
  2021-12-22 16:53 ` Stephen Hemminger
  0 siblings, 1 reply; 2+ messages in thread
From: fwefew 4t4tg @ 2021-12-20 18:22 UTC (permalink / raw)
  To: users

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My NIC has 32 RX and 32 TX queues.

Now given this API,

static uint16_t rte_eth_tx_burst ( uint16_t  port_id,
uint16_t  queue_id,
struct rte_mbuf <https://doc.dpdk.org/api/structrte__mbuf.html> **  tx_pkts,
uint16_t  nb_pkts
)
I gather the most natural approach for efficient packet transmissions is,

- assign one core to TX on a given port, queue since I/O through different
queues is essentially independent
- arrange packets in memory buffers so packets for the same queue are in
the same buffer

The RX side is much the same:

static uint16_t rte_eth_rx_burst ( uint16_t  port_id,
uint16_t  queue_id,
struct rte_mbuf <https://doc.dpdk.org/api/structrte__mbuf.html> **  rx_pkts,
const uint16_t  nb_pkts
)
- assign one core to RX on a given port, queue since I/O through different
queues is essentially independent of other queues

Is this pretty much the starting place?

Now, my NIC also has RSS (elided):

ethtool -x eth0

RSS hash key:

e8:27:27:e4:d9:fa:e4:1e:c6:89:67:95:52:4b:7a:41:3a:a6:68:5f:12:ec:4c:2f:51:18:a0:9b:bb:e1:7a:fb:a7:fb:7f:68:39:47:c2:83

RSS hash function:

    toeplitz: on

    xor: off

    crc32: off

But doesn't specifying the queue_id on RX/TX burst functions undercut RSS?
That is, nowhere is there an opportunity for the NIC to determine which
queue TX or RX go to since it was told at the outset?

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2021-12-20 18:22 Concept clarification on NICS with multiple queues fwefew 4t4tg
2021-12-22 16:53 ` Stephen Hemminger

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