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Message-Id: <1497526540-30028-6-git-send-email-tariqt@mellanox.com>
Date: Thu, 15 Jun 2017 14:35:35 +0300
From: Tariq Toukan <tariqt@...lanox.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: netdev@...r.kernel.org, Eran Ben Elisha <eranbe@...lanox.com>,
Saeed Mahameed <saeedm@...lanox.com>, kernel-team@...com,
Tariq Toukan <tariqt@...lanox.com>,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 05/10] 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 <tariqt@...lanox.com>
Reviewed-by: Saeed Mahameed <saeedm@...lanox.com>
Cc: kernel-team@...com
Cc: Eric Dumazet <edumazet@...gle.com>
---
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:
--
1.8.3.1
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