Re: [PATCH v3 net-next 2/2] tcp: minor optimization around tcp_hdr() usage in tcp receive path

[Eric Dumazet]

On 05/28/2018 05:41 PM, Yafang Shao wrote:

> OK.
> 
> And what about introducing a new helper tcp_hdr_fast() ?
> 
> /* use it when tcp header has not been pulled yet */
> static inline struct tcphdr *tcp_hdr_fast(const struct sk_buff *skb)
> 
> {
> 
> return (const struct tcphdr *)skb->data;
> 
> }
> 
> 
> That could help us to use this optimized one instead of the original
> one if possilbe.


I would rather not add such macro...

The call site needs to know what is going on, so having a macro like that would 
not help.

Re: [PATCH v3 net-next 2/2] tcp: minor optimization around tcp_hdr() usage in tcp receive path

[Yafang Shao]

On Tue, May 29, 2018 at 12:36 AM, Eric Dumazet  wrote:
> On Mon, May 28, 2018 at 8:36 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.
>
>> Cc: Eric Dumazet 
>> Signed-off-by: Yafang Shao 
>> ---
>>   net/ipv4/tcp_ipv4.c | 2 +-
>>   net/ipv6/tcp_ipv6.c | 2 +-
>>   2 files changed, 2 insertions(+), 2 deletions(-)
>
>> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
>> index adbdb50..d179386 100644
>> --- a/net/ipv4/tcp_ipv4.c
>> +++ b/net/ipv4/tcp_ipv4.c
>> @@ -1486,7 +1486,7 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff
> *skb)
>>  sk->sk_rx_dst = NULL;
>>  }
>>  }
>> -   tcp_rcv_established(sk, skb, tcp_hdr(skb));
>> +   tcp_rcv_established(sk, skb, (const struct tcphdr
> *)skb->data);
>>  return 0;
>>  }
>
>> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
>> index 7d47c2b..1c633ff 100644
>> --- a/net/ipv6/tcp_ipv6.c
>> +++ b/net/ipv6/tcp_ipv6.c
>> @@ -1322,7 +1322,7 @@ static int tcp_v6_do_rcv(struct sock *sk, struct
> sk_buff *skb)
>>  }
>>  }
>
>> -   tcp_rcv_established(sk, skb, tcp_hdr(skb));
>> +   tcp_rcv_established(sk, skb, (const struct tcphdr
> *)skb->data);
>>  if (opt_skb)
>>  goto ipv6_pktoptions;
>>  return 0;
>> --
>> 1.8.3.1
>
>
> I would rather remove the third parameter of tcp_rcv_established() instead
> of duplicating the cast.

OK.

And what about introducing a new helper tcp_hdr_fast() ?

/* use it when tcp header has not been pulled yet */
static inline struct tcphdr *tcp_hdr_fast(const struct sk_buff *skb)

{

return (const struct tcphdr *)skb->data;

}


That could help us to use this optimized one instead of the original
one if possilbe.

Thanks
Yafang

Re: [PATCH v3 net-next 2/2] tcp: minor optimization around tcp_hdr() usage in tcp receive path

[Eric Dumazet]

On Mon, May 28, 2018 at 8:36 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.

> Cc: Eric Dumazet 
> Signed-off-by: Yafang Shao 
> ---
>   net/ipv4/tcp_ipv4.c | 2 +-
>   net/ipv6/tcp_ipv6.c | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)

> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index adbdb50..d179386 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -1486,7 +1486,7 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff
*skb)
>  sk->sk_rx_dst = NULL;
>  }
>  }
> -   tcp_rcv_established(sk, skb, tcp_hdr(skb));
> +   tcp_rcv_established(sk, skb, (const struct tcphdr
*)skb->data);
>  return 0;
>  }

> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index 7d47c2b..1c633ff 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -1322,7 +1322,7 @@ static int tcp_v6_do_rcv(struct sock *sk, struct
sk_buff *skb)
>  }
>  }

> -   tcp_rcv_established(sk, skb, tcp_hdr(skb));
> +   tcp_rcv_established(sk, skb, (const struct tcphdr
*)skb->data);
>  if (opt_skb)
>  goto ipv6_pktoptions;
>  return 0;
> --
> 1.8.3.1


I would rather remove the third parameter of tcp_rcv_established() instead
of duplicating the cast.