> When fast releasing mbufs, the mbufs are not accessed, so do not prefetch
> them.
> This saves a mbuf load operation for each fast released TX mbuf.
>
> When fast release of mbufs is enabled for a TX queue, cache the mbuf
> mempool pointer in the TX queue structure.
> This saves one mbuf load operation for each burst of fast released TX
> mbufs.
>
> The txep->mbuf pointer is not used after the mbuf has been freed, so do
> not reset the pointer.
> This saves a txep store operation for each TX mbuf freed.
>
> Signed-off-by: Morten Brørup <m...@smartsharesystems.com>
> ---
> drivers/net/intel/common/tx.h | 5 +++
> .../i40e/i40e_recycle_mbufs_vec_common.c | 4 +-
> drivers/net/intel/i40e/i40e_rxtx.c | 39 ++++++++++---------
> 3 files changed, 28 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/net/intel/common/tx.h b/drivers/net/intel/common/tx.h
> index b0a68bae44..54c9b845f7 100644
> --- a/drivers/net/intel/common/tx.h
> +++ b/drivers/net/intel/common/tx.h
> @@ -62,6 +62,11 @@ struct ci_tx_queue {
> uint16_t tx_next_dd;
> uint16_t tx_next_rs;
> uint64_t offloads;
> + /* Mempool pointer for fast release of mbufs.
> + * NULL if disabled, UINTPTR_MAX if enabled and not yet known.
> + * Initialized at first use.
> + */
> + struct rte_mempool *fast_free_mp;
> uint64_t mbuf_errors;
> rte_iova_t tx_ring_dma; /* TX ring DMA address */
> bool tx_deferred_start; /* don't start this queue in dev start */
> diff --git a/drivers/net/intel/i40e/i40e_recycle_mbufs_vec_common.c
> b/drivers/net/intel/i40e/i40e_recycle_mbufs_vec_common.c
> index 2875c578af..a46605cee9 100644
> --- a/drivers/net/intel/i40e/i40e_recycle_mbufs_vec_common.c
> +++ b/drivers/net/intel/i40e/i40e_recycle_mbufs_vec_common.c
> @@ -106,7 +106,9 @@ i40e_recycle_tx_mbufs_reuse_vec(void *tx_queue,
> if (txq->offloads & RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE) {
> /* Avoid txq contains buffers from unexpected mempool. */
> if (unlikely(recycle_rxq_info->mp
> - != txep[0].mbuf->pool))
> + != (likely(txq->fast_free_mp != (void
> *)UINTPTR_MAX) ?
> + txq->fast_free_mp :
> + (txq->fast_free_mp = txep[0].mbuf->pool))))
> return 0;
>
> /* Directly put mbufs from Tx to Rx. */
> diff --git a/drivers/net/intel/i40e/i40e_rxtx.c
> b/drivers/net/intel/i40e/i40e_rxtx.c
> index c3ff2e05c3..679c1340b8 100644
> --- a/drivers/net/intel/i40e/i40e_rxtx.c
> +++ b/drivers/net/intel/i40e/i40e_rxtx.c
> @@ -1332,7 +1332,7 @@ static __rte_always_inline int
> i40e_tx_free_bufs(struct ci_tx_queue *txq)
> {
> struct ci_tx_entry *txep;
> - uint16_t tx_rs_thresh = txq->tx_rs_thresh;
> + const uint16_t tx_rs_thresh = txq->tx_rs_thresh;
> uint16_t i = 0, j = 0;
> struct rte_mbuf *free[RTE_I40E_TX_MAX_FREE_BUF_SZ];
> const uint16_t k = RTE_ALIGN_FLOOR(tx_rs_thresh,
> RTE_I40E_TX_MAX_FREE_BUF_SZ);
> @@ -1345,41 +1345,40 @@ i40e_tx_free_bufs(struct ci_tx_queue *txq)
>
> txep = &txq->sw_ring[txq->tx_next_dd - (tx_rs_thresh - 1)];
>
> - for (i = 0; i < tx_rs_thresh; i++)
> - rte_prefetch0((txep + i)->mbuf);
> -
> if (txq->offloads & RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE) {
> + struct rte_mempool * const fast_free_mp =
> + likely(txq->fast_free_mp != (void
> *)UINTPTR_MAX) ?
> + txq->fast_free_mp :
> + (txq->fast_free_mp = txep[0].mbuf->pool);
> +
Nit idea.
Acked-by: Konstantin Ananyev <konstantin.anan...@huawei.com>
Just as a suggestion for further improvement:
can we update (& check) txq->fast_free_mp not at tx_free_bufs() time,
but when we fill txep[] and filling txd[] based on mbuf values?
In theory it should allow to remove the check above.
Also, again in theory, it opens opportunity (with some extra effort) to use
similar optimization rte_mempool_put_bulk)
even for cases when RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE is not set.
> if (k) {
> for (j = 0; j != k; j += RTE_I40E_TX_MAX_FREE_BUF_SZ) {
> - for (i = 0; i < RTE_I40E_TX_MAX_FREE_BUF_SZ;
> ++i, ++txep) {
> + for (i = 0; i < RTE_I40E_TX_MAX_FREE_BUF_SZ;
> ++i, ++txep)
> free[i] = txep->mbuf;
> - txep->mbuf = NULL;
> - }
> - rte_mempool_put_bulk(free[0]->pool, (void
> **)free,
> + rte_mempool_put_bulk(fast_free_mp, (void
> **)free,
> RTE_I40E_TX_MAX_FREE_BUF_SZ);
> }
> }
>
> if (m) {
> - for (i = 0; i < m; ++i, ++txep) {
> + for (i = 0; i < m; ++i, ++txep)
> free[i] = txep->mbuf;
> - txep->mbuf = NULL;
> - }
> - rte_mempool_put_bulk(free[0]->pool, (void **)free, m);
> + rte_mempool_put_bulk(fast_free_mp, (void **)free, m);
> }
> } else {
> - for (i = 0; i < txq->tx_rs_thresh; ++i, ++txep) {
> + for (i = 0; i < tx_rs_thresh; i++)
> + rte_prefetch0((txep + i)->mbuf);
> +
> + for (i = 0; i < tx_rs_thresh; ++i, ++txep)
> rte_pktmbuf_free_seg(txep->mbuf);
> - txep->mbuf = NULL;
> - }
> }
>
> - txq->nb_tx_free = (uint16_t)(txq->nb_tx_free + txq->tx_rs_thresh);
> - txq->tx_next_dd = (uint16_t)(txq->tx_next_dd + txq->tx_rs_thresh);
> + txq->nb_tx_free = (uint16_t)(txq->nb_tx_free + tx_rs_thresh);
> + txq->tx_next_dd = (uint16_t)(txq->tx_next_dd + tx_rs_thresh);
> if (txq->tx_next_dd >= txq->nb_tx_desc)
> - txq->tx_next_dd = (uint16_t)(txq->tx_rs_thresh - 1);
> + txq->tx_next_dd = (uint16_t)(tx_rs_thresh - 1);
>
> - return txq->tx_rs_thresh;
> + return tx_rs_thresh;
> }
>
> /* Populate 4 descriptors with data from 4 mbufs */
> @@ -2546,6 +2545,8 @@ i40e_dev_tx_queue_setup(struct rte_eth_dev *dev,
> txq->reg_idx = reg_idx;
> txq->port_id = dev->data->port_id;
> txq->offloads = offloads;
> + txq->fast_free_mp = offloads & RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE ?
> + (void *)UINTPTR_MAX : NULL;
> txq->i40e_vsi = vsi;
> txq->tx_deferred_start = tx_conf->tx_deferred_start;
>
> --
> 2.43.0
