Re: [PATCH iwl-next v2 2/2] igc: enable build_skb on the non-XDP small-frame RX path

["Ruinskiy, Dima" <dima.ruinskiy@intel.com>]

On 17/03/2026 8:21, Kohei Enju wrote:
> igc implements igc_build_skb(), but it is currently unused because the
> IGC_RING_FLAG_RX_BUILD_SKB_ENABLED bit is never set. Enable the
> build_skb path when XDP is not active and the configured maximum frame
> size fits within IGC_MAX_FRAME_BUILD_SKB.
> 
> In a single-queue small-packet (64-byte) RX microbenchmark on my setup,
> enabling build_skb improved the receive rate from about 3.11 Mpps to
> about 3.30 Mpps, while reducing missed packets from about 484 kpps to
> about 300 kpps.
> 
> Keep the XDP path unchanged for now, since it uses a different RX buffer
> layout based on XDP_PACKET_HEADROOM, and enabling it there would need
> separate validation and buffer layout adjustments.
> 
> Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
> Signed-off-by: Kohei Enju <kohei@enjuk.jp>
> ---
>   drivers/net/ethernet/intel/igc/igc.h      | 4 ++++
>   drivers/net/ethernet/intel/igc/igc_main.c | 4 ++++
>   2 files changed, 8 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h
> index e66799507f81..acbd2c237667 100644
> --- a/drivers/net/ethernet/intel/igc/igc.h
> +++ b/drivers/net/ethernet/intel/igc/igc.h
> @@ -734,6 +734,10 @@ enum igc_ring_flags_t {
>   
>   #define ring_uses_build_skb(ring) \
>   	test_bit(IGC_RING_FLAG_RX_BUILD_SKB_ENABLED, &(ring)->flags)
> +#define set_ring_uses_build_skb(ring) \
> +	set_bit(IGC_RING_FLAG_RX_BUILD_SKB_ENABLED, &(ring)->flags)
> +#define clear_ring_uses_build_skb(ring) \
> +	clear_bit(IGC_RING_FLAG_RX_BUILD_SKB_ENABLED, &(ring)->flags)
>   
>   static inline unsigned int igc_rx_bufsz(struct igc_ring *ring)
>   {
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 79192b02e6be..b44f89311a4e 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -474,6 +474,7 @@ static void igc_clean_rx_ring(struct igc_ring *ring)
>   		igc_clean_rx_ring_page_shared(ring);
>   
>   	clear_ring_uses_large_buffer(ring);
> +	clear_ring_uses_build_skb(ring);
>   
>   	ring->next_to_alloc = 0;
>   	ring->next_to_clean = 0;
> @@ -654,6 +655,9 @@ static void igc_configure_rx_ring(struct igc_adapter *adapter,
>   
>   	if (igc_xdp_is_enabled(adapter))
>   		set_ring_uses_large_buffer(ring);
> +	else if (!(adapter->flags & IGC_FLAG_RX_LEGACY) &&
> +		 adapter->max_frame_size <= IGC_MAX_FRAME_BUILD_SKB)
> +		set_ring_uses_build_skb(ring);
>   
>   	/* disable the queue */
>   	wr32(IGC_RXDCTL(reg_idx), 0);
Reviewed-by: Dima Ruinskiy <dima.ruinskiy@intel.com>