> For TX mbuf fast release offload, I propose to add the mbuf mempool > pointer to the ethdev tx queue configuration structure, > so the ethdev TX burst operation doesn't need to fetch it from the > first mbuf of each burst being fast free'd to the mempool. > > This modification of the struct rte_eth_txconf, and the requirement > to set the mempool pointer if the RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE > flag is set, will be an API+ABI change in 25.11. > Should it be announced in the 25.07 release notes? > > Note: We could phase it in softly by letting the ethdev drivers > check if the pointer has been set, and fall back to fetching it > from mbuf[0] if not. > > /** > * A structure used to configure a Tx ring of an Ethernet port. > */ > struct rte_eth_txconf { > struct rte_eth_thresh tx_thresh; /**< Tx ring threshold registers. */ > uint16_t tx_rs_thresh; /**< Drives the setting of RS bit on TXDs. */ > uint16_t tx_free_thresh; /**< Start freeing Tx buffers if there are > less free descriptors than this value. */ > > uint8_t tx_deferred_start; /**< Do not start queue with > rte_eth_dev_start(). */ > /** > * Per-queue Tx offloads to be set using RTE_ETH_TX_OFFLOAD_* flags. > * Only offloads set on tx_queue_offload_capa or tx_offload_capa > * fields on rte_eth_dev_info structure are allowed to be set. > */ > uint64_t offloads; > > + /** > + * Per-queue mempool to release the mbufs to; required for > + * RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE offload. > + */ > + struct rte_mempool *mp; > +
Even though I usually recommend to use MBUF_FAST_FREE - that's probably a good change. At least people will realize that they have to provide a single mempool per TX queue when they enable FAST_FREE flag. One naming suggestion I have - can we name it somehow more informative: 'fast_free_mp' or so? Also, we can update tx_queue_setup() to catch the situation when FAST_FREE is set but mp is NULL, or visa-versa. Again drivers can probably add extra check when debug is enabled, that all mbufs are exactly from that mempool. > uint64_t reserved_64s[2]; /**< Reserved for future fields */ > void *reserved_ptrs[2]; /**< Reserved for future fields */ > }; >