> Subject: [PATCH v3] net/intel: optimize for fast-free hint
>
snip
> diff --git a/drivers/net/intel/common/tx_scalar.h
> b/drivers/net/intel/common/tx_scalar.h
> index 9fcd2e4733..d27df34dfa 100644
> --- a/drivers/net/intel/common/tx_scalar.h
> +++ b/drivers/net/intel/common/tx_scalar.h
> @@ -197,16 +197,64 @@ ci_tx_xmit_cleanup(struct ci_tx_queue *txq)
> const uint16_t rs_idx = (last_desc_cleaned == nb_tx_desc - 1) ?
> 0 :
> (last_desc_cleaned + 1) >> txq->log2_rs_thresh;
> - uint16_t desc_to_clean_to = (rs_idx << txq->log2_rs_thresh) + (txq-
> >tx_rs_thresh - 1);
> + const uint16_t dd_idx = txq->rs_last_id[rs_idx];
> + const uint16_t first_to_clean = rs_idx << txq->log2_rs_thresh;
>
> - /* Check if descriptor is done */
> - if ((txd[txq->rs_last_id[rs_idx]].cmd_type_offset_bsz &
> - rte_cpu_to_le_64(CI_TXD_QW1_DTYPE_M)) !=
> -
> rte_cpu_to_le_64(CI_TX_DESC_DTYPE_DESC_DONE))
> + /* Check if descriptor is done - all drivers use 0xF as done value in
> bits
> 3:0 */
> + if ((txd[dd_idx].cmd_type_offset_bsz &
> rte_cpu_to_le_64(CI_TXD_QW1_DTYPE_M)) !=
> + rte_cpu_to_le_64(CI_TX_DESC_DTYPE_DESC_DONE))
> + /* Descriptor not yet processed by hardware */
> return -1;
>
> + /* DD bit is set, descriptors are done. Now free the mbufs. */
> + /* Note: nb_tx_desc is guaranteed to be a multiple of tx_rs_thresh,
> + * validated during queue setup. This means cleanup never wraps
> around
> + * the ring within a single burst (e.g., ring=256, rs_thresh=32 gives
> + * bursts of 0-31, 32-63, ..., 224-255).
> + */
> + const uint16_t nb_to_clean = txq->tx_rs_thresh;
> + struct ci_tx_entry *sw_ring = txq->sw_ring;
> +
> + /* fast_free_mp is NULL only when the fast free is disabled*/
> + if (txq->fast_free_mp != NULL) {
> + /* FAST_FREE path: mbufs are already reset, just return to
> pool */
> + struct rte_mbuf *free[CI_TX_MAX_FREE_BUF_SZ];
> + uint16_t nb_free = 0;
> +
> + /* Get cached mempool pointer, or cache it on first use */
> + struct rte_mempool *mp =
> + likely(txq->fast_free_mp != (void *)UINTPTR_MAX) ?
> + txq->fast_free_mp :
> + (txq->fast_free_mp = sw_ring[dd_idx].mbuf->pool);
Is the mbuf you are dereferencing here guaranteed to be non NULL?
Other than that concern:
Acked-by: Ciara Loftus <[email protected]>
> +
> + /* Pack non-NULL mbufs in-place at start of sw_ring range.
> + * No modulo needed in loop since we're guaranteed not to
> wrap.
> + */
> + for (uint16_t i = 0; i < nb_to_clean; i++) {
