From f28186d6b55d4c0b315d025753c22927e836a0e2 Mon Sep 17 00:00:00 2001 From: Tariq Toukan Date: Thu, 15 Jun 2017 14:35:35 +0300 Subject: [PATCH] net/mlx4_en: Improve stack xmit function Several small code and performance improvements in stack TX datapath, including: - Compiler branch predictor hints. - Minimize variables scope. - Move tx_info non-inline flow handling to a separate function. - Calculate data_offset in compile time rather than in runtime (for !lso_header_size branch). - Avoid trinary-operator ("?") when value can be preset in a matching branch. Performance tests: Tested on ConnectX3Pro, Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz Gain is too small to be measurable, no degradation sensed. Results are similar for IPv4 and IPv6. Signed-off-by: Tariq Toukan Reviewed-by: Saeed Mahameed Cc: kernel-team@fb.com Cc: Eric Dumazet Signed-off-by: David S. Miller --- drivers/net/ethernet/mellanox/mlx4/en_tx.c | 151 ++++++++++++--------- 1 file changed, 87 insertions(+), 64 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c index 2d5e0da1de2f..58f4b322587b 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c @@ -774,37 +774,101 @@ static void mlx4_en_tx_write_desc(struct mlx4_en_tx_ring *ring, } } +static bool mlx4_en_build_dma_wqe(struct mlx4_en_priv *priv, + struct skb_shared_info *shinfo, + struct mlx4_wqe_data_seg *data, + struct sk_buff *skb, + int lso_header_size, + __be32 mr_key, + struct mlx4_en_tx_info *tx_info) +{ + struct device *ddev = priv->ddev; + dma_addr_t dma = 0; + u32 byte_count = 0; + int i_frag; + + /* Map fragments if any */ + for (i_frag = shinfo->nr_frags - 1; i_frag >= 0; i_frag--) { + const struct skb_frag_struct *frag; + + frag = &shinfo->frags[i_frag]; + byte_count = skb_frag_size(frag); + dma = skb_frag_dma_map(ddev, frag, + 0, byte_count, + DMA_TO_DEVICE); + if (dma_mapping_error(ddev, dma)) + goto tx_drop_unmap; + + data->addr = cpu_to_be64(dma); + data->lkey = mr_key; + dma_wmb(); + data->byte_count = cpu_to_be32(byte_count); + --data; + } + + /* Map linear part if needed */ + if (tx_info->linear) { + byte_count = skb_headlen(skb) - lso_header_size; + + dma = dma_map_single(ddev, skb->data + + lso_header_size, byte_count, + PCI_DMA_TODEVICE); + if (dma_mapping_error(ddev, dma)) + goto tx_drop_unmap; + + data->addr = cpu_to_be64(dma); + data->lkey = mr_key; + dma_wmb(); + data->byte_count = cpu_to_be32(byte_count); + } + /* tx completion can avoid cache line miss for common cases */ + tx_info->map0_dma = dma; + tx_info->map0_byte_count = byte_count; + + return true; + +tx_drop_unmap: + en_err(priv, "DMA mapping error\n"); + + while (++i_frag < shinfo->nr_frags) { + ++data; + dma_unmap_page(ddev, (dma_addr_t)be64_to_cpu(data->addr), + be32_to_cpu(data->byte_count), + PCI_DMA_TODEVICE); + } + + return false; +} + netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) { struct skb_shared_info *shinfo = skb_shinfo(skb); struct mlx4_en_priv *priv = netdev_priv(dev); union mlx4_wqe_qpn_vlan qpn_vlan = {}; - struct device *ddev = priv->ddev; struct mlx4_en_tx_ring *ring; struct mlx4_en_tx_desc *tx_desc; struct mlx4_wqe_data_seg *data; struct mlx4_en_tx_info *tx_info; - int tx_ind = 0; + int tx_ind; int nr_txbb; int desc_size; int real_size; u32 index, bf_index; __be32 op_own; - u16 vlan_proto = 0; - int i_frag; int lso_header_size; void *fragptr = NULL; bool bounce = false; bool send_doorbell; bool stop_queue; bool inline_ok; + u8 data_offset; u32 ring_cons; bool bf_ok; tx_ind = skb_get_queue_mapping(skb); ring = priv->tx_ring[TX][tx_ind]; - if (!priv->port_up) + if (unlikely(!priv->port_up)) goto tx_drop; /* fetch ring->cons far ahead before needing it to avoid stall */ @@ -826,6 +890,8 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) bf_ok = ring->bf_enabled; if (skb_vlan_tag_present(skb)) { + u16 vlan_proto; + qpn_vlan.vlan_tag = cpu_to_be16(skb_vlan_tag_get(skb)); vlan_proto = be16_to_cpu(skb->vlan_proto); if (vlan_proto == ETH_P_8021AD) @@ -862,64 +928,31 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) tx_info->skb = skb; tx_info->nr_txbb = nr_txbb; - data = &tx_desc->data; - if (lso_header_size) - data = ((void *)&tx_desc->lso + ALIGN(lso_header_size + 4, - DS_SIZE)); + if (!lso_header_size) { + data = &tx_desc->data; + data_offset = offsetof(struct mlx4_en_tx_desc, data); + } else { + int lso_align = ALIGN(lso_header_size + 4, DS_SIZE); + + data = (void *)&tx_desc->lso + lso_align; + data_offset = offsetof(struct mlx4_en_tx_desc, lso) + lso_align; + } /* valid only for none inline segments */ - tx_info->data_offset = (void *)data - (void *)tx_desc; + tx_info->data_offset = data_offset; tx_info->inl = inline_ok; - tx_info->linear = (lso_header_size < skb_headlen(skb) && - !inline_ok) ? 1 : 0; + tx_info->linear = lso_header_size < skb_headlen(skb) && !inline_ok; tx_info->nr_maps = shinfo->nr_frags + tx_info->linear; data += tx_info->nr_maps - 1; - if (!tx_info->inl) { - dma_addr_t dma = 0; - u32 byte_count = 0; - - /* Map fragments if any */ - for (i_frag = shinfo->nr_frags - 1; i_frag >= 0; i_frag--) { - const struct skb_frag_struct *frag; - - frag = &shinfo->frags[i_frag]; - byte_count = skb_frag_size(frag); - dma = skb_frag_dma_map(ddev, frag, - 0, byte_count, - DMA_TO_DEVICE); - if (dma_mapping_error(ddev, dma)) - goto tx_drop_unmap; - - data->addr = cpu_to_be64(dma); - data->lkey = ring->mr_key; - dma_wmb(); - data->byte_count = cpu_to_be32(byte_count); - --data; - } - - /* Map linear part if needed */ - if (tx_info->linear) { - byte_count = skb_headlen(skb) - lso_header_size; - - dma = dma_map_single(ddev, skb->data + - lso_header_size, byte_count, - PCI_DMA_TODEVICE); - if (dma_mapping_error(ddev, dma)) - goto tx_drop_unmap; - - data->addr = cpu_to_be64(dma); - data->lkey = ring->mr_key; - dma_wmb(); - data->byte_count = cpu_to_be32(byte_count); - } - /* tx completion can avoid cache line miss for common cases */ - tx_info->map0_dma = dma; - tx_info->map0_byte_count = byte_count; - } + if (!tx_info->inl) + if (!mlx4_en_build_dma_wqe(priv, shinfo, data, skb, + lso_header_size, ring->mr_key, + tx_info)) + goto tx_drop_count; /* * For timestamping add flag to skb_shinfo and @@ -1055,16 +1088,6 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) } return NETDEV_TX_OK; -tx_drop_unmap: - en_err(priv, "DMA mapping error\n"); - - while (++i_frag < shinfo->nr_frags) { - ++data; - dma_unmap_page(ddev, (dma_addr_t) be64_to_cpu(data->addr), - be32_to_cpu(data->byte_count), - PCI_DMA_TODEVICE); - } - tx_drop_count: ring->tx_dropped++; tx_drop: -- 2.30.2