> From: Konstantin Ananyev [mailto:konstantin.anan...@huawei.com] > Sent: Friday, 4 July 2025 18.20 > > > 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.
Correction in your other mail noted: "[...] NOT to use MBUF_FAST_FREE" > 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? I was planning to put information about the field in the comments only, but yes, we can name it "fast_free_mp". > Also, we can update tx_queue_setup() to catch the situation when > FAST_FREE > is set but mp is NULL, or visa-versa. Yes, that was the plan. (Although I didn't think about the "vice-versa" case, which is also a good thing to catch.) > Again drivers can probably add extra check when debug is enabled, that > all mbufs are exactly from that mempool. I recently added the rte_mbuf_raw_free_bulk() function to the mbuf API, to emphasize the requirements that drivers must comply to when fast-freeing mbufs. And for verification purposes, when conformance testing drivers' fast-free implementation. Drivers should use this mbuf API instead of directly interacting with the mempool API when bulk freeing mbufs. > > > > uint64_t reserved_64s[2]; /**< Reserved for future fields */ > > void *reserved_ptrs[2]; /**< Reserved for future fields */ > > }; > >
