From: Christoph Paasch Date: Mon, 1 Jun 2026 06:15:22 +0000 (+0300) Subject: net/mlx5e: Avoid copying payload to the skb's linear part X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=399f030cd6123f1b3539d1557a6e956eb1cd7da7;p=thirdparty%2Flinux.git net/mlx5e: Avoid copying payload to the skb's linear part mlx5e_skb_from_cqe_mpwrq_nonlinear() copies MLX5E_RX_MAX_HEAD (256) bytes from the page-pool to the skb's linear part. Those 256 bytes include part of the payload. When attempting to do GRO in skb_gro_receive, if headlen > data_offset (and skb->head_frag is not set), we end up aggregating packets in the frag_list. This is of course not good when we are CPU-limited. Also causes a worse skb->len/truesize ratio,... So, let's avoid copying parts of the payload to the linear part. We use eth_get_headlen() to parse the headers and compute the length of the protocol headers, which will be used to copy the relevant bits of the skb's linear part. We still allocate MLX5E_RX_MAX_HEAD for the skb so that if the networking stack needs to call pskb_may_pull() later on, we don't need to reallocate memory. This gives a nice throughput increase (ARM Neoverse-V2 with CX-7 NIC and LRO enabled): BEFORE: ======= (netserver pinned to core receiving interrupts) $ netperf -H 10.221.81.118 -T 80,9 -P 0 -l 60 -- -m 256K -M 256K 87380 16384 262144 60.01 32547.82 (netserver pinned to adjacent core receiving interrupts) $ netperf -H 10.221.81.118 -T 80,10 -P 0 -l 60 -- -m 256K -M 256K 87380 16384 262144 60.00 52531.67 AFTER: ====== (netserver pinned to core receiving interrupts) $ netperf -H 10.221.81.118 -T 80,9 -P 0 -l 60 -- -m 256K -M 256K 87380 16384 262144 60.00 52896.06 (netserver pinned to adjacent core receiving interrupts) $ netperf -H 10.221.81.118 -T 80,10 -P 0 -l 60 -- -m 256K -M 256K 87380 16384 262144 60.00 85094.90 Additional tests across a larger range of parameters w/ and w/o LRO, w/ and w/o IPv6-encapsulation, different MTUs (1500, 4096, 9000), different TCP read/write-sizes as well as UDP benchmarks, all have shown equal or better performance with this patch. For XDP pull at most ETH_HLEN bytes in the linear area so that XDP_PASS can also benefit from this improvement and keep things simple when dealing with skb geometry changes from the XDP program. Reviewed-by: Eric Dumazet Reviewed-by: Saeed Mahameed Signed-off-by: Christoph Paasch Signed-off-by: Dragos Tatulea Signed-off-by: Tariq Toukan Link: https://patch.msgid.link/20260601061522.398044-3-tariqt@nvidia.com Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c index 75ccf40a7f17..6fbc0441c4b8 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c @@ -1912,7 +1912,6 @@ mlx5e_skb_from_cqe_mpwrq_nonlinear(struct mlx5e_rq *rq, struct mlx5e_mpw_info *w u32 page_idx) { struct mlx5e_frag_page *frag_page = &wi->alloc_units.frag_pages[page_idx]; - u16 headlen = min_t(u16, MLX5E_RX_MAX_HEAD, cqe_bcnt); struct mlx5e_frag_page *head_page = frag_page; struct mlx5e_frag_page *linear_page = NULL; struct mlx5e_xdp_buff *mxbuf = &rq->mxbuf; @@ -1928,6 +1927,7 @@ mlx5e_skb_from_cqe_mpwrq_nonlinear(struct mlx5e_rq *rq, struct mlx5e_mpw_info *w u32 linear_frame_sz; u16 linear_data_len; u16 linear_hr; + u16 headlen; if (unlikely(cqe_bcnt > rq->hw_mtu)) { u8 lro_num_seg = get_cqe_lro_num_seg(cqe); @@ -1971,11 +1971,14 @@ mlx5e_skb_from_cqe_mpwrq_nonlinear(struct mlx5e_rq *rq, struct mlx5e_mpw_info *w net_prefetchw(va); /* xdp_frame data area */ net_prefetchw(skb->data); + headlen = min(MLX5E_RX_MAX_HEAD, cqe_bcnt); addr = page_pool_get_dma_addr_netmem(head_page->netmem); dma_sync_single_for_cpu(rq->pdev, addr + head_offset, ALIGN(headlen, sizeof(long)), rq->buff.map_dir); + headlen = eth_get_headlen(rq->netdev, head_addr, headlen); + frag_offset += headlen; byte_cnt -= headlen; linear_hr = skb_headroom(skb); @@ -2060,9 +2063,9 @@ mlx5e_skb_from_cqe_mpwrq_nonlinear(struct mlx5e_rq *rq, struct mlx5e_mpw_info *w pagep->frags++; while (++pagep < frag_page); - headlen = min_t(u16, MLX5E_RX_MAX_HEAD - len, - skb->data_len); - __pskb_pull_tail(skb, headlen); + if (len < ETH_HLEN) + __pskb_pull_tail(skb, min(ETH_HLEN - len, + skb->data_len)); } } else { if (xdp_buff_has_frags(&mxbuf->xdp)) {