linux-kernel - Re: [PATCH v3 net-next v3 3/6] net: add code for TCP fraglist GRO

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Date: Fri, 26 Apr 2024 09:47:30 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Felix Fietkau <nbd@....name>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, 
	David Ahern <dsahern@...nel.org>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	willemdebruijn.kernel@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 net-next v3 3/6] net: add code for TCP fraglist GRO

On Fri, Apr 26, 2024 at 8:51 AM Felix Fietkau <nbd@....name> wrote:
>
> This implements fraglist GRO similar to how it's handled in UDP, however
> no functional changes are added yet. The next change adds a heuristic for
> using fraglist GRO instead of regular GRO.
>
> Signed-off-by: Felix Fietkau <nbd@....name>
> ---
>  net/ipv4/tcp_offload.c   | 22 ++++++++++++++++++++++
>  net/ipv6/tcpv6_offload.c |  9 +++++++++
>  2 files changed, 31 insertions(+)
>
> diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
> index c493e95e09a5..ffd6b7a4163a 100644
> --- a/net/ipv4/tcp_offload.c
> +++ b/net/ipv4/tcp_offload.c
> @@ -332,6 +332,19 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
>         flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
>         flush |= skb_cmp_decrypted(p, skb);
>
> +       if (NAPI_GRO_CB(p)->is_flist) {


Please add unlikely() for all NAPI_GRO_CB(p)->is_flist checks added in
this patch.

> +               flush |= (__force int)(flags ^ tcp_flag_word(th2));
> +               flush |= skb->ip_summed != p->ip_summed;
> +               flush |= skb->csum_level != p->csum_level;
> +               flush |= !pskb_may_pull(skb, skb_gro_offset(skb));
> +               flush |= NAPI_GRO_CB(p)->count >= 64;
> +
> +               if (flush || skb_gro_receive_list(p, skb))
> +                       mss = 1;
> +
> +               goto out_check_final;
> +       }
> +
>         if (flush || skb_gro_receive(p, skb)) {
>                 mss = 1;
>                 goto out_check_final;
> @@ -398,6 +411,15 @@ INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
>         const struct iphdr *iph = ip_hdr(skb);
>         struct tcphdr *th = tcp_hdr(skb);
>
> +       if (NAPI_GRO_CB(skb)->is_flist) {
> +               skb_shinfo(skb)->gso_type |= SKB_GSO_FRAGLIST | SKB_GSO_TCPV4;
> +               skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
> +
> +               __skb_incr_checksum_unnecessary(skb);
> +
> +               return 0;
> +       }
> +
>         th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
>                                   iph->daddr, 0);
>
> diff --git a/net/ipv6/tcpv6_offload.c b/net/ipv6/tcpv6_offload.c
> index b3b8e1f6b92a..c97d55cf036f 100644
> --- a/net/ipv6/tcpv6_offload.c
> +++ b/net/ipv6/tcpv6_offload.c
> @@ -32,6 +32,15 @@ INDIRECT_CALLABLE_SCOPE int tcp6_gro_complete(struct sk_buff *skb, int thoff)
>         const struct ipv6hdr *iph = ipv6_hdr(skb);
>         struct tcphdr *th = tcp_hdr(skb);
>
> +       if (NAPI_GRO_CB(skb)->is_flist) {
> +               skb_shinfo(skb)->gso_type |= SKB_GSO_FRAGLIST | SKB_GSO_TCPV6;
> +               skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
> +
> +               __skb_incr_checksum_unnecessary(skb);
> +
> +               return 0;
> +       }
> +
>         th->check = ~tcp_v6_check(skb->len - thoff, &iph->saddr,
>                                   &iph->daddr, 0);
>         skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV6;
> --
> 2.44.0
>