linux-kernel - Re: [PATCH v4 net-next 2/2] tcp: minor optimization around tcp

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Date:   Tue, 29 May 2018 06:54:27 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Yafang Shao <laoar.shao@...il.com>, songliubraving@...com,
        edumazet@...gle.com, davem@...emloft.net
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 net-next 2/2] tcp: minor optimization around tcp_hdr()
 usage in tcp receive path



On 05/29/2018 06:35 AM, Yafang Shao wrote:
> This is additional to the commit ea1627c20c34 ("tcp: minor optimizations around tcp_hdr() usage").
> At this point, skb->data is same with tcp_hdr() as tcp header has not
> been pulled yet.
> Remove the third parameter of tcp_rcv_established() and put it into
> the function body.
> 
> Cc: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> 
> ---
> v4: remove the third parameter of tcp_rcv_established()
> ---
>  include/net/tcp.h    | 3 +--
>  net/ipv4/tcp_input.c | 4 ++--
>  net/ipv4/tcp_ipv4.c  | 2 +-
>  net/ipv6/tcp_ipv6.c  | 2 +-
>  4 files changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 952d842..029a51b 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -334,8 +334,7 @@ ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
>  void tcp_delack_timer_handler(struct sock *sk);
>  int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
>  int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
> -void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
> -			 const struct tcphdr *th);
> +void tcp_rcv_established(struct sock *sk, struct sk_buff *skb);
>  void tcp_rcv_space_adjust(struct sock *sk);
>  int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
>  void tcp_twsk_destructor(struct sock *sk);
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index 1191cac..1d70dab 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -5390,11 +5390,11 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
>   *	the rest is checked inline. Fast processing is turned on in
>   *	tcp_data_queue when everything is OK.
>   */
> -void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
> -			 const struct tcphdr *th)
> +void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
>  {
>  	unsigned int len = skb->len;
>  	struct tcp_sock *tp = tcp_sk(sk);
> +	const struct tcphdr *th = (const struct tcphdr *)skb->data;
>  
>

Please reorder list to get a reverse christmas tree.

const struct tcphdr *th = (const struct tcphdr *)skb->data;
struct tcp_sock *tp = tcp_sk(sk);
unsigned int len = skb->len;