When the fast-free hint is provided to the driver we know that the mbufs have refcnt of 1 and are from the same mempool. Therefore, we can optimize a bit for this case by:
* resetting the necessary mbuf fields, ie. nb_seg and next pointer when we are accessing the mbuf on writing the descriptor. * on cleanup of buffers after transmit, we can just write those buffers straight to the mempool without accessing them. * when doing buffer cleanup, we can follow the model of the vector driver where we cleanup in fixed bursts which don't wrap, and where we track the mbufs between tx_tail and last_cleaned as invalid, so we don't need to set them to NULL. [We only set to NULL valid mbuf slots where we have a context descriptor or segment not backed by an mbuf] Signed-off-by: Bruce Richardson <[email protected]> --- v3: * used mbuf_raw_free_bulk rather than mempool function directly * check for fast_free via mp pointer rather than flags * remove unnecessary prefetches V2: Fix issues with original submission: * missed check for NULL mbufs * fixed issue with freeing directly from sw_ring in scalar path which doesn't work as thats not a flag array of pointers * fixed missing null assignment in case of large segments for TSO --- drivers/net/intel/common/tx.h | 21 ++++-- drivers/net/intel/common/tx_scalar.h | 99 +++++++++++++++++++++------- 2 files changed, 92 insertions(+), 28 deletions(-) diff --git a/drivers/net/intel/common/tx.h b/drivers/net/intel/common/tx.h index 23a8c39cf2..5fe71aed12 100644 --- a/drivers/net/intel/common/tx.h +++ b/drivers/net/intel/common/tx.h @@ -329,13 +329,22 @@ ci_txq_release_all_mbufs(struct ci_tx_queue *txq, bool use_ctx) return; if (!txq->use_vec_entry) { - /* Regular scalar path uses sw_ring with ci_tx_entry */ - for (uint16_t i = 0; i < txq->nb_tx_desc; i++) { - if (txq->sw_ring[i].mbuf != NULL) { - rte_pktmbuf_free_seg(txq->sw_ring[i].mbuf); - txq->sw_ring[i].mbuf = NULL; - } + /* Free mbufs from (last_desc_cleaned + 1) to (tx_tail - 1). */ + const uint16_t start = (txq->last_desc_cleaned + 1) % txq->nb_tx_desc; + const uint16_t nb_desc = txq->nb_tx_desc; + const uint16_t end = txq->tx_tail; + + uint16_t i = start; + if (end < i) { + for (; i < nb_desc; i++) + if (txq->sw_ring[i].mbuf != NULL) + rte_pktmbuf_free_seg(txq->sw_ring[i].mbuf); + i = 0; } + for (; i < end; i++) + if (txq->sw_ring[i].mbuf != NULL) + rte_pktmbuf_free_seg(txq->sw_ring[i].mbuf); + memset(txq->sw_ring, 0, sizeof(txq->sw_ring[0]) * nb_desc); return; } 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); + + /* 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++) { + struct rte_mbuf *m = sw_ring[first_to_clean + i].mbuf; + if (m == NULL) + continue; + free[nb_free++] = m; + if (unlikely(nb_free == CI_TX_MAX_FREE_BUF_SZ)) { + rte_mbuf_raw_free_bulk(mp, free, nb_free); + nb_free = 0; + } + } + + /* Bulk return to mempool using packed sw_ring entries directly */ + if (nb_free > 0) + rte_mbuf_raw_free_bulk(mp, free, nb_free); + } else { + /* Non-FAST_FREE path: use free_seg for refcount checks and freeing */ + for (uint16_t i = 0; i < nb_to_clean; i++) { + struct rte_mbuf *m = sw_ring[first_to_clean + i].mbuf; + if (m != NULL) + rte_pktmbuf_free_seg(m); + } + } + /* Update the txq to reflect the last descriptor that was cleaned */ - txq->last_desc_cleaned = desc_to_clean_to; + txq->last_desc_cleaned = first_to_clean + txq->tx_rs_thresh - 1; txq->nb_tx_free += txq->tx_rs_thresh; return 0; @@ -450,8 +498,6 @@ ci_xmit_pkts(struct ci_tx_queue *txq, txd = &ci_tx_ring[tx_id]; tx_id = txe->next_id; - if (txe->mbuf) - rte_pktmbuf_free_seg(txe->mbuf); txe->mbuf = tx_pkt; /* Setup TX Descriptor */ td_cmd |= CI_TX_DESC_CMD_EOP; @@ -471,11 +517,7 @@ ci_xmit_pkts(struct ci_tx_queue *txq, uint64_t *ctx_txd = RTE_CAST_PTR(uint64_t *, &ci_tx_ring[tx_id]); txn = &sw_ring[txe->next_id]; - RTE_MBUF_PREFETCH_TO_FREE(txn->mbuf); - if (txe->mbuf) { - rte_pktmbuf_free_seg(txe->mbuf); - txe->mbuf = NULL; - } + txe->mbuf = NULL; write_txd(ctx_txd, cd_qw0, cd_qw1); @@ -488,11 +530,7 @@ ci_xmit_pkts(struct ci_tx_queue *txq, uint64_t *ipsec_txd = RTE_CAST_PTR(uint64_t *, &ci_tx_ring[tx_id]); txn = &sw_ring[txe->next_id]; - RTE_MBUF_PREFETCH_TO_FREE(txn->mbuf); - if (txe->mbuf) { - rte_pktmbuf_free_seg(txe->mbuf); - txe->mbuf = NULL; - } + txe->mbuf = NULL; ipsec_txd[0] = ipsec_qw0; ipsec_txd[1] = ipsec_qw1; @@ -507,10 +545,22 @@ ci_xmit_pkts(struct ci_tx_queue *txq, txd = &ci_tx_ring[tx_id]; txn = &sw_ring[txe->next_id]; - if (txe->mbuf) - rte_pktmbuf_free_seg(txe->mbuf); txe->mbuf = m_seg; + /* For FAST_FREE: reset mbuf fields while we have it in cache. + * [Fast free is indicated by txq->fast_free_mp being non-NULL.] + * FAST_FREE guarantees refcnt=1 and direct mbufs, so we only + * need to reset nb_segs and next pointer as per rte_pktmbuf_prefree_seg. + * Save next pointer before resetting since we need it for loop iteration. + */ + struct rte_mbuf *next_seg = m_seg->next; + if (txq->fast_free_mp != NULL) { + if (m_seg->nb_segs != 1) + m_seg->nb_segs = 1; + if (next_seg != NULL) + m_seg->next = NULL; + } + /* Setup TX Descriptor */ /* Calculate segment length, using IPsec callback if provided */ if (ipsec_ops != NULL) @@ -528,18 +578,23 @@ ci_xmit_pkts(struct ci_tx_queue *txq, ((uint64_t)CI_MAX_DATA_PER_TXD << CI_TXD_QW1_TX_BUF_SZ_S) | ((uint64_t)td_tag << CI_TXD_QW1_L2TAG1_S); write_txd(txd, buf_dma_addr, cmd_type_offset_bsz); + /* txe for this slot has already been written (e.g. above outside + * loop), so we write the extra NULL mbuf pointer for this + * descriptor after we increment txe below. + */ buf_dma_addr += CI_MAX_DATA_PER_TXD; slen -= CI_MAX_DATA_PER_TXD; tx_id = txe->next_id; txe = txn; + txe->mbuf = NULL; txd = &ci_tx_ring[tx_id]; txn = &sw_ring[txe->next_id]; } /* fill the last descriptor with End of Packet (EOP) bit */ - if (m_seg->next == NULL) + if (next_seg == NULL) td_cmd |= CI_TX_DESC_CMD_EOP; const uint64_t cmd_type_offset_bsz = CI_TX_DESC_DTYPE_DATA | @@ -551,7 +606,7 @@ ci_xmit_pkts(struct ci_tx_queue *txq, tx_id = txe->next_id; txe = txn; - m_seg = m_seg->next; + m_seg = next_seg; } while (m_seg); end_pkt: txq->nb_tx_free = (uint16_t)(txq->nb_tx_free - nb_used); -- 2.53.0
