netdev - [PATCH net-next 1/2] xsk: introduce XDP_GENERIC_XMIT

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Message-Id: <20250811131236.56206-2-kerneljasonxing@gmail.com>
Date: Mon, 11 Aug 2025 21:12:35 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	bjorn@...nel.org,
	magnus.karlsson@...el.com,
	maciej.fijalkowski@...el.com,
	jonathan.lemon@...il.com,
	sdf@...ichev.me,
	ast@...nel.org,
	daniel@...earbox.net,
	hawk@...nel.org,
	john.fastabend@...il.com,
	horms@...nel.org,
	andrew+netdev@...n.ch
Cc: bpf@...r.kernel.org,
	netdev@...r.kernel.org,
	Jason Xing <kernelxing@...cent.com>
Subject: [PATCH net-next 1/2] xsk: introduce XDP_GENERIC_XMIT_BATCH setsockopt

From: Jason Xing <kernelxing@...cent.com>

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.

Signed-off-by: Jason Xing <kernelxing@...cent.com>
---
 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