On Mon, Aug 11, 2025 at 09:12:35PM +0800, Jason Xing wrote:
> From: Jason Xing <kernelxing@xxxxxxxxxxx>
>
> This patch is to prepare for later batch xmit in generic path. Add a new
> socket option to provide an alternative to achieve a higher overall
> throughput.
>
> skb_batch will be used to store newly allocated skb at one time in the
> xmit path.
I don't think we need yet another setsockopt. You previously added a knob
for manipulating max tx budget on generic xmit and that should be enough.
I think that we should strive for making the batching approach a default
path in xsk generic xmit.
>
> Signed-off-by: Jason Xing <kernelxing@xxxxxxxxxxx>
> ---
> Documentation/networking/af_xdp.rst | 9 ++++++++
> include/net/xdp_sock.h | 2 ++
> include/uapi/linux/if_xdp.h | 1 +
> net/xdp/xsk.c | 32 +++++++++++++++++++++++++++++
> tools/include/uapi/linux/if_xdp.h | 1 +
> 5 files changed, 45 insertions(+)
>
> diff --git a/Documentation/networking/af_xdp.rst b/Documentation/networking/af_xdp.rst
> index 50d92084a49c..1194bdfaf61e 100644
> --- a/Documentation/networking/af_xdp.rst
> +++ b/Documentation/networking/af_xdp.rst
> @@ -447,6 +447,15 @@ mode to allow application to tune the per-socket maximum iteration for
> better throughput and less frequency of send syscall.
> Allowed range is [32, xs->tx->nentries].
>
> +XDP_GENERIC_XMIT_BATCH
> +----------------------
> +
> +It provides an option that allows application to use batch xmit in the copy
> +mode. Batch process minimizes the number of grabbing/releasing queue lock
> +without redundant actions compared to before to gain the overall performance
> +improvement whereas it might increase the latency of per packet. The maximum
> +value shouldn't be larger than xs->max_tx_budget.
> +
> XDP_STATISTICS getsockopt
> -------------------------
>
> diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
> index ce587a225661..b5a3e37da8db 100644
> --- a/include/net/xdp_sock.h
> +++ b/include/net/xdp_sock.h
> @@ -61,6 +61,7 @@ struct xdp_sock {
> XSK_BOUND,
> XSK_UNBOUND,
> } state;
> + struct sk_buff **skb_batch;
>
> struct xsk_queue *tx ____cacheline_aligned_in_smp;
> struct list_head tx_list;
> @@ -70,6 +71,7 @@ struct xdp_sock {
> * preventing other XSKs from being starved.
> */
> u32 tx_budget_spent;
> + u32 generic_xmit_batch;
>
> /* Statistics */
> u64 rx_dropped;
> diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
> index 23a062781468..44cb72cd328e 100644
> --- a/include/uapi/linux/if_xdp.h
> +++ b/include/uapi/linux/if_xdp.h
> @@ -80,6 +80,7 @@ struct xdp_mmap_offsets {
> #define XDP_STATISTICS 7
> #define XDP_OPTIONS 8
> #define XDP_MAX_TX_SKB_BUDGET 9
> +#define XDP_GENERIC_XMIT_BATCH 10
>
> struct xdp_umem_reg {
> __u64 addr; /* Start of packet data area */
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 9c3acecc14b1..7a149f4ac273 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -1122,6 +1122,7 @@ static int xsk_release(struct socket *sock)
> xskq_destroy(xs->tx);
> xskq_destroy(xs->fq_tmp);
> xskq_destroy(xs->cq_tmp);
> + kfree(xs->skb_batch);
>
> sock_orphan(sk);
> sock->sk = NULL;
> @@ -1456,6 +1457,37 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname,
> WRITE_ONCE(xs->max_tx_budget, budget);
> return 0;
> }
> + case XDP_GENERIC_XMIT_BATCH:
> + {
> + unsigned int batch, batch_alloc_len;
> + struct sk_buff **new;
> +
> + if (optlen != sizeof(batch))
> + return -EINVAL;
> + if (copy_from_sockptr(&batch, optval, sizeof(batch)))
> + return -EFAULT;
> + if (batch > xs->max_tx_budget)
> + return -EACCES;
> +
> + mutex_lock(&xs->mutex);
> + if (!batch) {
> + kfree(xs->skb_batch);
> + xs->generic_xmit_batch = 0;
> + goto out;
> + }
> + batch_alloc_len = sizeof(struct sk_buff *) * batch;
> + new = kmalloc(batch_alloc_len, GFP_KERNEL);
> + if (!new)
> + return -ENOMEM;
> + if (xs->skb_batch)
> + kfree(xs->skb_batch);
> +
> + xs->skb_batch = new;
> + xs->generic_xmit_batch = batch;
> +out:
> + mutex_unlock(&xs->mutex);
> + return 0;
> + }
> default:
> break;
> }
> diff --git a/tools/include/uapi/linux/if_xdp.h b/tools/include/uapi/linux/if_xdp.h
> index 23a062781468..44cb72cd328e 100644
> --- a/tools/include/uapi/linux/if_xdp.h
> +++ b/tools/include/uapi/linux/if_xdp.h
> @@ -80,6 +80,7 @@ struct xdp_mmap_offsets {
> #define XDP_STATISTICS 7
> #define XDP_OPTIONS 8
> #define XDP_MAX_TX_SKB_BUDGET 9
> +#define XDP_GENERIC_XMIT_BATCH 10
>
> struct xdp_umem_reg {
> __u64 addr; /* Start of packet data area */
> --
> 2.41.3
>
