On Wed, 4 Mar 2026 17:03:36 +0100
Larysa Zaremba <larysa.zaremba@intel.com> wrote:
> Add likely/unlikely markers for better branch prediction. While touching
> some functions, cleanup the code a little bit.
>
> This patch is not supposed to make any logic changes aside from making
> total_rx_bytes and total_rx_packets more correlated.
>
> Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
> Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
> Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
> ---
> .../net/ethernet/intel/ixgbevf/ixgbevf_main.c | 29 +++++++++----------
> 1 file changed, 14 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> index 5a270dd2c7aa..4619f2bea1ab 100644
> --- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> +++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> @@ -570,7 +570,7 @@ static void ixgbevf_alloc_rx_buffers(struct ixgbevf_ring *rx_ring,
> u16 ntu = rx_ring->next_to_use;
>
> /* nothing to do or no valid netdev defined */
> - if (!cleaned_count || !rx_ring->netdev)
> + if (unlikely(!cleaned_count || !rx_ring->netdev))
> return;
>
> rx_desc = IXGBEVF_RX_DESC(rx_ring, ntu);
> @@ -586,7 +586,7 @@ static void ixgbevf_alloc_rx_buffers(struct ixgbevf_ring *rx_ring,
>
> rx_desc++;
> ntu++;
> - if (unlikely(ntu == rx_ring->count)) {
> + if (unlikely(ntu == fq.count)) {
> rx_desc = IXGBEVF_RX_DESC(rx_ring, 0);
> ntu = 0;
> }
> @@ -823,7 +823,7 @@ static int ixgbevf_clean_rx_irq(struct ixgbevf_q_vector *q_vector,
>
> rx_desc = IXGBEVF_RX_DESC(rx_ring, rx_ring->next_to_clean);
> size = le16_to_cpu(rx_desc->wb.upper.length);
> - if (!size)
> + if (unlikely(!size))
> break;
>
> /* This memory barrier is needed to keep us from reading
> @@ -855,7 +855,7 @@ static int ixgbevf_clean_rx_irq(struct ixgbevf_q_vector *q_vector,
> }
>
> /* exit if we failed to retrieve a buffer */
> - if (!xdp_res && !skb) {
> + if (unlikely(!xdp_res && !skb)) {
I'd check that generates something sensible.
Using unlikely on multi-term conditionals doesn't always do
something sensible.
David
> rx_ring->rx_stats.alloc_rx_buff_failed++;
> break;
> }
> @@ -867,21 +867,19 @@ static int ixgbevf_clean_rx_irq(struct ixgbevf_q_vector *q_vector,
> continue;
>
> /* verify the packet layout is correct */
> - if (xdp_res || ixgbevf_cleanup_headers(rx_ring, rx_desc, skb)) {
> + if (xdp_res ||
> + unlikely(ixgbevf_cleanup_headers(rx_ring, rx_desc, skb))) {
> skb = NULL;
> continue;
> }
>
> - /* probably a little skewed due to removing CRC */
> - total_rx_bytes += skb->len;
> -
> /* Workaround hardware that can't do proper VEPA multicast
> * source pruning.
> */
> - if ((skb->pkt_type == PACKET_BROADCAST ||
> - skb->pkt_type == PACKET_MULTICAST) &&
> - ether_addr_equal(rx_ring->netdev->dev_addr,
> - eth_hdr(skb)->h_source)) {
> + if (unlikely((skb->pkt_type == PACKET_BROADCAST ||
> + skb->pkt_type == PACKET_MULTICAST) &&
> + ether_addr_equal(rx_ring->netdev->dev_addr,
> + eth_hdr(skb)->h_source))) {
> dev_kfree_skb_irq(skb);
> continue;
> }
> @@ -889,13 +887,14 @@ static int ixgbevf_clean_rx_irq(struct ixgbevf_q_vector *q_vector,
> /* populate checksum, VLAN, and protocol */
> ixgbevf_process_skb_fields(rx_ring, rx_desc, skb);
>
> + /* probably a little skewed due to removing CRC */
> + total_rx_bytes += skb->len;
> + total_rx_packets++;
> +
> ixgbevf_rx_skb(q_vector, skb);
>
> /* reset skb pointer */
> skb = NULL;
> -
> - /* update budget accounting */
> - total_rx_packets++;
> }
>
> /* place incomplete frames back on ring for completion */