net/mlx4_en: Replace TXBB_SIZE multiplications with shift operations

Define LOG_TXBB_SIZE, log of TXBB_SIZE, and use it with a shift
operation instead of a multiplication with TXBB_SIZE.
Operations are equivalent as TXBB_SIZE is a power of two.

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@mellanox.com>
Reviewed-by: Saeed Mahameed <saeedm@mellanox.com>
Cc: kernel-team@fb.com
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index 500442c..efc4411 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -234,23 +234,24 @@ static void mlx4_en_stamp_wqe(struct mlx4_en_priv *priv,
                              u8 owner)
 {
        __be32 stamp = cpu_to_be32(STAMP_VAL | (!!owner << STAMP_SHIFT));
-       struct mlx4_en_tx_desc *tx_desc = ring->buf + index * TXBB_SIZE;
+       struct mlx4_en_tx_desc *tx_desc = ring->buf + (index << LOG_TXBB_SIZE);
        struct mlx4_en_tx_info *tx_info = &ring->tx_info[index];
        void *end = ring->buf + ring->buf_size;
        __be32 *ptr = (__be32 *)tx_desc;
        int i;
 
        /* Optimize the common case when there are no wraparounds */
-       if (likely((void *)tx_desc + tx_info->nr_txbb * TXBB_SIZE <= end)) {
+       if (likely((void *)tx_desc +
+                  (tx_info->nr_txbb << LOG_TXBB_SIZE) <= end)) {
                /* Stamp the freed descriptor */
-               for (i = 0; i < tx_info->nr_txbb * TXBB_SIZE;
+               for (i = 0; i < tx_info->nr_txbb << LOG_TXBB_SIZE;
                     i += STAMP_STRIDE) {
                        *ptr = stamp;
                        ptr += STAMP_DWORDS;
                }
        } else {
                /* Stamp the freed descriptor */
-               for (i = 0; i < tx_info->nr_txbb * TXBB_SIZE;
+               for (i = 0; i < tx_info->nr_txbb << LOG_TXBB_SIZE;
                     i += STAMP_STRIDE) {
                        *ptr = stamp;
                        ptr += STAMP_DWORDS;
@@ -269,7 +270,7 @@ u32 mlx4_en_free_tx_desc(struct mlx4_en_priv *priv,
                         int napi_mode)
 {
        struct mlx4_en_tx_info *tx_info = &ring->tx_info[index];
-       struct mlx4_en_tx_desc *tx_desc = ring->buf + index * TXBB_SIZE;
+       struct mlx4_en_tx_desc *tx_desc = ring->buf + (index << LOG_TXBB_SIZE);
        struct mlx4_wqe_data_seg *data = (void *) tx_desc + tx_info->data_offset;
        void *end = ring->buf + ring->buf_size;
        struct sk_buff *skb = tx_info->skb;
@@ -289,7 +290,8 @@ u32 mlx4_en_free_tx_desc(struct mlx4_en_priv *priv,
        }
 
        /* Optimize the common case when there are no wraparounds */
-       if (likely((void *) tx_desc + tx_info->nr_txbb * TXBB_SIZE <= end)) {
+       if (likely((void *)tx_desc +
+                  (tx_info->nr_txbb << LOG_TXBB_SIZE) <= end)) {
                if (!tx_info->inl) {
                        if (tx_info->linear)
                                dma_unmap_single(priv->ddev,
@@ -542,7 +544,7 @@ static struct mlx4_en_tx_desc *mlx4_en_bounce_to_desc(struct mlx4_en_priv *priv,
                                                      u32 index,
                                                      unsigned int desc_size)
 {
-       u32 copy = (ring->size - index) * TXBB_SIZE;
+       u32 copy = (ring->size - index) << LOG_TXBB_SIZE;
        int i;
 
        for (i = desc_size - copy - 4; i >= 0; i -= 4) {
@@ -557,12 +559,12 @@ static struct mlx4_en_tx_desc *mlx4_en_bounce_to_desc(struct mlx4_en_priv *priv,
                if ((i & (TXBB_SIZE - 1)) == 0)
                        wmb();
 
-               *((u32 *) (ring->buf + index * TXBB_SIZE + i)) =
+               *((u32 *)(ring->buf + (index << LOG_TXBB_SIZE) + i)) =
                        *((u32 *) (ring->bounce_buf + i));
        }
 
        /* Return real descriptor location */
-       return ring->buf + index * TXBB_SIZE;
+       return ring->buf + (index << LOG_TXBB_SIZE);
 }
 
 /* Decide if skb can be inlined in tx descriptor to avoid dma mapping
@@ -881,7 +883,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 
        /* Align descriptor to TXBB size */
        desc_size = ALIGN(real_size, TXBB_SIZE);
-       nr_txbb = desc_size / TXBB_SIZE;
+       nr_txbb = desc_size >> LOG_TXBB_SIZE;
        if (unlikely(nr_txbb > MAX_DESC_TXBBS)) {
                if (netif_msg_tx_err(priv))
                        en_warn(priv, "Oversized header or SG list\n");
@@ -916,7 +918,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
        /* See if we have enough space for whole descriptor TXBB for setting
         * SW ownership on next descriptor; if not, use a bounce buffer. */
        if (likely(index + nr_txbb <= ring->size))
-               tx_desc = ring->buf + index * TXBB_SIZE;
+               tx_desc = ring->buf + (index << LOG_TXBB_SIZE);
        else {
                tx_desc = (struct mlx4_en_tx_desc *) ring->bounce_buf;
                bounce = true;
@@ -1129,7 +1131,7 @@ netdev_tx_t mlx4_en_xmit_frame(struct mlx4_en_rx_ring *rx_ring,
        AVG_PERF_COUNTER(priv->pstats.inflight_avg,
                         (u32)(ring->prod - READ_ONCE(ring->cons) - 1));
 
-       tx_desc = ring->buf + index * TXBB_SIZE;
+       tx_desc = ring->buf + (index << LOG_TXBB_SIZE);
        data = &tx_desc->data;
 
        dma = frame->dma;

diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
index 7f61b58..963b77d 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
+++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
@@ -72,7 +72,8 @@
 #define DEF_RX_RINGS           16
 #define MAX_RX_RINGS           128
 #define MIN_RX_RINGS           4
-#define TXBB_SIZE              64
+#define LOG_TXBB_SIZE          6
+#define TXBB_SIZE              BIT(LOG_TXBB_SIZE)
 #define HEADROOM               (2048 / TXBB_SIZE + 1)
 #define STAMP_STRIDE           64
 #define STAMP_DWORDS           (STAMP_STRIDE / 4)