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Message-ID: <CALzJLG-rNgKSroZg5+XsHRF8vPb=+b4V2cSchAz3c6+cvOW96w@mail.gmail.com>
Date: Thu, 9 Feb 2017 19:15:59 +0200
From: Saeed Mahameed <saeedm@....mellanox.co.il>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>,
netdev <netdev@...r.kernel.org>,
Tariq Toukan <tariqt@...lanox.com>,
Martin KaFai Lau <kafai@...com>,
Willem de Bruijn <willemb@...gle.com>,
Jesper Dangaard Brouer <brouer@...hat.com>,
Brenden Blanco <bblanco@...mgrid.com>,
Alexei Starovoitov <ast@...nel.org>,
Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH v2 net-next 14/14] mlx4: remove duplicate code in mlx4_en_process_rx_cq()
On Thu, Feb 9, 2017 at 3:58 PM, Eric Dumazet <edumazet@...gle.com> wrote:
> We should keep one way to build skbs, regardless of GRO being on or off.
>
> Note that I made sure to defer as much as possible the point we need to
> pull data from the frame, so that future prefetch() we might add
> are more effective.
>
> These skb attributes derive from the CQE or ring :
> ip_summed, csum
> hash
> vlan offload
> hwtstamps
> queue_mapping
>
> As a bonus, this patch removes mlx4 dependency on eth_get_headlen()
So no copy at all in driver RX ? as it is handled in
napi_gro_frags(&cq->napi); ?
General question, why not just use build_skb() ? which approach is better ?
> which is very often broken enough to give us headaches.
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
> drivers/net/ethernet/mellanox/mlx4/en_rx.c | 203 ++++++-----------------------
> 1 file changed, 37 insertions(+), 166 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> index 0a87cc96e90ce7374821a0b4712d4b85ad8e..ef6c295789803a69f7066f7e5c80d1dc37f2 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> @@ -526,64 +526,6 @@ static int mlx4_en_complete_rx_desc(struct mlx4_en_priv *priv,
> return 0;
> }
>
> -
> -static struct sk_buff *mlx4_en_rx_skb(struct mlx4_en_priv *priv,
> - struct mlx4_en_rx_alloc *frags,
> - unsigned int length)
> -{
> - struct sk_buff *skb;
> - void *va;
> - int used_frags;
> - dma_addr_t dma;
> -
> - skb = netdev_alloc_skb(priv->dev, SMALL_PACKET_SIZE + NET_IP_ALIGN);
> - if (unlikely(!skb)) {
> - en_dbg(RX_ERR, priv, "Failed allocating skb\n");
> - return NULL;
> - }
> - skb_reserve(skb, NET_IP_ALIGN);
> - skb->len = length;
> -
> - /* Get pointer to first fragment so we could copy the headers into the
> - * (linear part of the) skb */
> - va = page_address(frags[0].page) + frags[0].page_offset;
> -
> - if (length <= SMALL_PACKET_SIZE) {
> - /* We are copying all relevant data to the skb - temporarily
> - * sync buffers for the copy */
> -
> - dma = frags[0].dma + frags[0].page_offset;
> - dma_sync_single_for_cpu(priv->ddev, dma, length,
> - DMA_FROM_DEVICE);
> - skb_copy_to_linear_data(skb, va, length);
> - skb->tail += length;
> - } else {
> - unsigned int pull_len;
> -
> - /* Move relevant fragments to skb */
> - used_frags = mlx4_en_complete_rx_desc(priv, frags,
> - skb, length);
> - if (unlikely(!used_frags)) {
> - kfree_skb(skb);
> - return NULL;
> - }
> - skb_shinfo(skb)->nr_frags = used_frags;
> -
> - pull_len = eth_get_headlen(va, SMALL_PACKET_SIZE);
> - /* Copy headers into the skb linear buffer */
> - memcpy(skb->data, va, pull_len);
> - skb->tail += pull_len;
> -
> - /* Skip headers in first fragment */
> - skb_shinfo(skb)->frags[0].page_offset += pull_len;
> -
> - /* Adjust size of first fragment */
> - skb_frag_size_sub(&skb_shinfo(skb)->frags[0], pull_len);
> - skb->data_len = length - pull_len;
> - }
> - return skb;
> -}
> -
> static void validate_loopback(struct mlx4_en_priv *priv, void *va)
> {
> const unsigned char *data = va + ETH_HLEN;
> @@ -792,8 +734,6 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
> */
> length = be32_to_cpu(cqe->byte_cnt);
> length -= ring->fcs_del;
> - l2_tunnel = (dev->hw_enc_features & NETIF_F_RXCSUM) &&
> - (cqe->vlan_my_qpn & cpu_to_be32(MLX4_CQE_L2_TUNNEL));
>
> /* A bpf program gets first chance to drop the packet. It may
> * read bytes but not past the end of the frag.
> @@ -849,122 +789,51 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
> ring->bytes += length;
> ring->packets++;
>
> + skb = napi_get_frags(&cq->napi);
> + if (!skb)
> + goto next;
> +
> + if (unlikely(ring->hwtstamp_rx_filter == HWTSTAMP_FILTER_ALL)) {
> + timestamp = mlx4_en_get_cqe_ts(cqe);
> + mlx4_en_fill_hwtstamps(mdev, skb_hwtstamps(skb),
> + timestamp);
> + }
> + skb_record_rx_queue(skb, cq->ring);
> +
> if (likely(dev->features & NETIF_F_RXCSUM)) {
> if (cqe->status & cpu_to_be16(MLX4_CQE_STATUS_TCP |
> MLX4_CQE_STATUS_UDP)) {
> if ((cqe->status & cpu_to_be16(MLX4_CQE_STATUS_IPOK)) &&
> cqe->checksum == cpu_to_be16(0xffff)) {
> ip_summed = CHECKSUM_UNNECESSARY;
> + l2_tunnel = (dev->hw_enc_features & NETIF_F_RXCSUM) &&
> + (cqe->vlan_my_qpn & cpu_to_be32(MLX4_CQE_L2_TUNNEL));
> + if (l2_tunnel)
> + skb->csum_level = 1;
> ring->csum_ok++;
> } else {
> - ip_summed = CHECKSUM_NONE;
> - ring->csum_none++;
> + goto csum_none;
> }
> } else {
> if (priv->flags & MLX4_EN_FLAG_RX_CSUM_NON_TCP_UDP &&
> (cqe->status & cpu_to_be16(MLX4_CQE_STATUS_IPV4 |
> MLX4_CQE_STATUS_IPV6))) {
> - ip_summed = CHECKSUM_COMPLETE;
> - ring->csum_complete++;
> + if (check_csum(cqe, skb, va, dev->features)) {
> + goto csum_none;
> + } else {
> + ip_summed = CHECKSUM_COMPLETE;
> + ring->csum_complete++;
> + }
> } else {
> - ip_summed = CHECKSUM_NONE;
> - ring->csum_none++;
> + goto csum_none;
> }
> }
> } else {
> +csum_none:
> ip_summed = CHECKSUM_NONE;
> ring->csum_none++;
> }
Why just not move this whole csum logic to a dedicated function ?
all it needs to do is update some csum statistics and determine
"ip_summed" value;
> -
> - /* This packet is eligible for GRO if it is:
> - * - DIX Ethernet (type interpretation)
> - * - TCP/IP (v4)
> - * - without IP options
> - * - not an IP fragment
> - */
> - if (dev->features & NETIF_F_GRO) {
> - struct sk_buff *gro_skb = napi_get_frags(&cq->napi);
> - if (!gro_skb)
> - goto next;
> -
> - nr = mlx4_en_complete_rx_desc(priv, frags, gro_skb,
> - length);
> - if (!nr)
> - goto next;
> -
> - if (ip_summed == CHECKSUM_COMPLETE) {
> - if (check_csum(cqe, gro_skb, va,
> - dev->features)) {
> - ip_summed = CHECKSUM_NONE;
> - ring->csum_none++;
> - ring->csum_complete--;
> - }
> - }
> -
> - skb_shinfo(gro_skb)->nr_frags = nr;
> - gro_skb->len = length;
> - gro_skb->data_len = length;
> - gro_skb->ip_summed = ip_summed;
> -
> - if (l2_tunnel && ip_summed == CHECKSUM_UNNECESSARY)
> - gro_skb->csum_level = 1;
> -
> - if ((cqe->vlan_my_qpn &
> - cpu_to_be32(MLX4_CQE_CVLAN_PRESENT_MASK)) &&
> - (dev->features & NETIF_F_HW_VLAN_CTAG_RX)) {
> - u16 vid = be16_to_cpu(cqe->sl_vid);
> -
> - __vlan_hwaccel_put_tag(gro_skb, htons(ETH_P_8021Q), vid);
> - } else if ((be32_to_cpu(cqe->vlan_my_qpn) &
> - MLX4_CQE_SVLAN_PRESENT_MASK) &&
> - (dev->features & NETIF_F_HW_VLAN_STAG_RX)) {
> - __vlan_hwaccel_put_tag(gro_skb,
> - htons(ETH_P_8021AD),
> - be16_to_cpu(cqe->sl_vid));
> - }
> -
> - if (dev->features & NETIF_F_RXHASH)
> - skb_set_hash(gro_skb,
> - be32_to_cpu(cqe->immed_rss_invalid),
> - (ip_summed == CHECKSUM_UNNECESSARY) ?
> - PKT_HASH_TYPE_L4 :
> - PKT_HASH_TYPE_L3);
> -
> - skb_record_rx_queue(gro_skb, cq->ring);
> -
> - if (ring->hwtstamp_rx_filter == HWTSTAMP_FILTER_ALL) {
> - timestamp = mlx4_en_get_cqe_ts(cqe);
> - mlx4_en_fill_hwtstamps(mdev,
> - skb_hwtstamps(gro_skb),
> - timestamp);
> - }
> -
> - napi_gro_frags(&cq->napi);
> - goto next;
> - }
> -
> - /* GRO not possible, complete processing here */
> - skb = mlx4_en_rx_skb(priv, frags, length);
> - if (unlikely(!skb)) {
> - ring->dropped++;
> - goto next;
> - }
> -
> - if (ip_summed == CHECKSUM_COMPLETE) {
> - if (check_csum(cqe, skb, va, dev->features)) {
> - ip_summed = CHECKSUM_NONE;
> - ring->csum_complete--;
> - ring->csum_none++;
> - }
> - }
> -
Finally! Best patch ever !
Thank you Eric.
> skb->ip_summed = ip_summed;
> - skb->protocol = eth_type_trans(skb, dev);
Not required anymore ? I know napi_frags_skb does the job,
but what about skb->pkt_type field which is handled in eth_type_trans ?
> - skb_record_rx_queue(skb, cq->ring);
> -
> - if (l2_tunnel && ip_summed == CHECKSUM_UNNECESSARY)
> - skb->csum_level = 1;
> -
> if (dev->features & NETIF_F_RXHASH)
> skb_set_hash(skb,
> be32_to_cpu(cqe->immed_rss_invalid),
> @@ -972,23 +841,25 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
> PKT_HASH_TYPE_L4 :
> PKT_HASH_TYPE_L3);
>
> - if ((be32_to_cpu(cqe->vlan_my_qpn) &
> - MLX4_CQE_CVLAN_PRESENT_MASK) &&
> +
> + if ((cqe->vlan_my_qpn &
> + cpu_to_be32(MLX4_CQE_CVLAN_PRESENT_MASK)) &&
> (dev->features & NETIF_F_HW_VLAN_CTAG_RX))
> - __vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), be16_to_cpu(cqe->sl_vid));
> - else if ((be32_to_cpu(cqe->vlan_my_qpn) &
> - MLX4_CQE_SVLAN_PRESENT_MASK) &&
> + __vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q),
> + be16_to_cpu(cqe->sl_vid));
> + else if ((cqe->vlan_my_qpn &
> + cpu_to_be32(MLX4_CQE_SVLAN_PRESENT_MASK)) &&
> (dev->features & NETIF_F_HW_VLAN_STAG_RX))
> __vlan_hwaccel_put_tag(skb, htons(ETH_P_8021AD),
> be16_to_cpu(cqe->sl_vid));
>
> - if (ring->hwtstamp_rx_filter == HWTSTAMP_FILTER_ALL) {
> - timestamp = mlx4_en_get_cqe_ts(cqe);
> - mlx4_en_fill_hwtstamps(mdev, skb_hwtstamps(skb),
> - timestamp);
> + nr = mlx4_en_complete_rx_desc(priv, frags, skb, length);
> + if (nr) {
likely() ?
> + skb_shinfo(skb)->nr_frags = nr;
> + skb->len = length;
> + skb->data_len = length;
> + napi_gro_frags(&cq->napi);
> }
no need to kfree_skb/reset some SKB fields in case nr == 0 ?
since this SKB will be returned via napi_get_frags if you didn't
actually consume it ..
for example 1st packet is a valn packet and for some reason
mlx4_en_complete_rx_desc returned 0 on it.
next packet is a non vlan packet that will get the same skb of the 1st
packet with non clean SKB fields such as (skb->vlan_tci) !
> -
> - napi_gro_receive(&cq->napi, skb);
> next:
> ++cq->mcq.cons_index;
> index = (cq->mcq.cons_index) & ring->size_mask;
> --
> 2.11.0.483.g087da7b7c-goog
>
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