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charset="UTF-8" On Tue, Nov 3, 2026 at 3:51 PM Stanislav Fomichev wrote: > > TX bindings use PAGE_SIZE net_iovs, so a frag covers at most a page. > A 64KB skb needs 16 frags, and MAX_SKB_FRAGS caps devmem skbs at about > 68KB, which makes BIG TCP ineffective for devmem TX. > > This series picks the TX net_iov size from the dmabuf sg table instead: > the largest power of 2, up to 2MB, which aligns every DMA segment. With > a 2MB hugepage-backed udmabuf a BIG TCP skb takes a few frags. There's > no UAPI change since TX addresses are dmabuf offsets. > > TCP still bounds skbs by size_goal, so frags get larger, skbs don't. > A single frag can now be as large as the skb, which matters for > NETMEM_TX drivers with tso_max_size above 64KB: > - mlx5: 32-bit length per data segment > - gve: splits frags into 16KB descriptors > - fbnic: keeps the default 64KB tso_max_size > - bnxt: 16-bit BD length, devmem TX frags are capped at 32KB by a new > per-device limit Reviewed-by: Mina Almasry