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Diffstat (limited to 'doc/guides/nics/enic.rst')
| -rw-r--r-- | doc/guides/nics/enic.rst | 53 |
1 files changed, 48 insertions, 5 deletions
diff --git a/doc/guides/nics/enic.rst b/doc/guides/nics/enic.rst index 42e781e3..26692022 100644 --- a/doc/guides/nics/enic.rst +++ b/doc/guides/nics/enic.rst @@ -59,11 +59,31 @@ Configuration information - **Number of Queues** - The maximum number of receive and transmit queues are configurable on a per - vNIC basis through the Cisco UCS Manager (CIMC or UCSM). These values - should be configured to be greater than or equal to the nb_rx_q and nb_tx_q - parameters expected to used in the call to the rte_eth_dev_configure() - function. + The maximum number of receive queues (RQs), work queues (WQs) and + completion queues (CQs) are configurable on a per vNIC basis + through the Cisco UCS Manager (CIMC or UCSM). + + These values should be configured as follows: + + - The number of WQs should be greater or equal to the value of the + expected nb_tx_q parameter in the call to the + rte_eth_dev_configure() + + - The number of RQs configured in the vNIC should be greater or + equal to *twice* the value of the expected nb_rx_q parameter in + the call to rte_eth_dev_configure(). With the addition of rx + scatter, a pair of RQs on the vnic is needed for each receive + queue used by DPDK, even if rx scatter is not being used. + Having a vNIC with only 1 RQ is not a valid configuration, and + will fail with an error message. + + - The number of CQs should set so that there is one CQ for each + WQ, and one CQ for each pair of RQs. + + For example: If the application requires 3 Rx queues, and 3 Tx + queues, the vNIC should be configured to have at least 3 WQs, 6 + RQs (3 pairs), and 6 CQs (3 for use by WQs + 3 for use by the 3 + pairs of RQs). - **Size of Queues** @@ -71,6 +91,29 @@ Configuration information a per vNIC bases via the UCS Manager and should be greater than or equal to the nb_rx_desc and nb_tx_desc parameters expected to be used in the calls to rte_eth_rx_queue_setup() and rte_eth_tx_queue_setup() respectively. + An application requesting more than the set size will be limited to that + size. + + Unless there is a lack of resources due to creating many vNICs, it + is recommended that the WQ and RQ sizes be set to the maximum. This + gives the application the greatest amount of flexibility in its + queue configuration. + + - *Note*: Since the introduction of rx scatter, for performance + reasons, this PMD uses two RQs on the vNIC per receive queue in + DPDK. One RQ holds descriptors for the start of a packet the + second RQ holds the descriptors for the rest of the fragments of + a packet. This means that the nb_rx_desc parameter to + rte_eth_rx_queue_setup() can be a greater than 4096. The exact + amount will depend on the size of the mbufs being used for + receives, and the MTU size. + + For example: If the mbuf size is 2048, and the MTU is 9000, then + receiving a full size packet will take 5 descriptors, 1 from the + start of packet queue, and 4 from the second queue. Assuming + that the RQ size was set to the maximum of 4096, then the + application can specify up to 1024 + 4096 as the nb_rx_desc + parameter to rte_eth_rx_queue_setup(). - **Interrupts** |