netdev - Re: [PATCH bpf-next 3/3] ice: xsk: borrow xdp_tx

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Date:   Mon, 13 Dec 2021 14:13:01 +0100
From:   Magnus Karlsson <magnus.karlsson@...il.com>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Network Development <netdev@...r.kernel.org>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>
Subject: Re: [PATCH bpf-next 3/3] ice: xsk: borrow xdp_tx_active logic from i40e

On Sat, Dec 11, 2021 at 3:02 AM Maciej Fijalkowski
<maciej.fijalkowski@...el.com> wrote:
>
> One of the things that commit 5574ff7b7b3d ("i40e: optimize AF_XDP Tx
> completion path") introduced was the @xdp_tx_active field. Its usage
> from i40e can be adjusted to ice driver and give us positive performance
> results.
>
> If the descriptor that @next_dd to points has been sent by HW (its DD
> bit is set), then we are sure that there are ICE_TX_THRESH count of
> descriptors ready to be cleaned. If @xdp_tx_active is 0 which means that
> related xdp_ring is not used for XDP_{TX, REDIRECT} workloads, then we
> know how many XSK entries should placed to completion queue, IOW walking
> through the ring can be skipped.

Thanks for implementing this in ice too.

Acked-by: Magnus Karlsson <magnus.karlsson@...el.com>

> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> ---
>  drivers/net/ethernet/intel/ice/ice_txrx.h     | 1 +
>  drivers/net/ethernet/intel/ice/ice_txrx_lib.c | 1 +
>  drivers/net/ethernet/intel/ice/ice_xsk.c      | 7 +++++++
>  3 files changed, 9 insertions(+)
>
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.h b/drivers/net/ethernet/intel/ice/ice_txrx.h
> index f2ebbe2158e7..8dd9c92662ad 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx.h
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx.h
> @@ -332,6 +332,7 @@ struct ice_tx_ring {
>         struct ice_ptp_tx *tx_tstamps;
>         spinlock_t tx_lock;
>         u32 txq_teid;                   /* Added Tx queue TEID */
> +       u16 xdp_tx_active;
>  #define ICE_TX_FLAGS_RING_XDP          BIT(0)
>         u8 flags;
>         u8 dcb_tc;                      /* Traffic class of ring */
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
> index 1dd7e84f41f8..f15c215c973c 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
> @@ -299,6 +299,7 @@ int ice_xmit_xdp_ring(void *data, u16 size, struct ice_tx_ring *xdp_ring)
>         tx_desc->cmd_type_offset_bsz = ice_build_ctob(ICE_TX_DESC_CMD_EOP, 0,
>                                                       size, 0);
>
> +       xdp_ring->xdp_tx_active++;
>         i++;
>         if (i == xdp_ring->count) {
>                 i = 0;
> diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
> index a7f866b3fcd7..8949a7be45c6 100644
> --- a/drivers/net/ethernet/intel/ice/ice_xsk.c
> +++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
> @@ -684,6 +684,7 @@ static void
>  ice_clean_xdp_tx_buf(struct ice_tx_ring *xdp_ring, struct ice_tx_buf *tx_buf)
>  {
>         xdp_return_frame((struct xdp_frame *)tx_buf->raw_buf);
> +       xdp_ring->xdp_tx_active--;
>         dma_unmap_single(xdp_ring->dev, dma_unmap_addr(tx_buf, dma),
>                          dma_unmap_len(tx_buf, len), DMA_TO_DEVICE);
>         dma_unmap_len_set(tx_buf, len, 0);
> @@ -713,6 +714,11 @@ bool ice_clean_tx_irq_zc(struct ice_tx_ring *xdp_ring)
>
>  again:
>         xsk_frames = 0;
> +       if (likely(!xdp_ring->xdp_tx_active)) {
> +               xsk_frames = ICE_TX_THRESH;
> +               goto skip;
> +       }
> +
>         ntc = xdp_ring->next_to_clean;
>
>         for (i = 0; i < ICE_TX_THRESH; i++) {
> @@ -729,6 +735,7 @@ bool ice_clean_tx_irq_zc(struct ice_tx_ring *xdp_ring)
>                 if (ntc >= xdp_ring->count)
>                         ntc = 0;
>         }
> +skip:
>         xdp_ring->next_to_clean += ICE_TX_THRESH;
>         if (xdp_ring->next_to_clean >= desc_cnt)
>                 xdp_ring->next_to_clean -= desc_cnt;
> --
> 2.33.1
>