netdev - Re: [PATCH] tcp_input: move out condition check from tcp_data

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Date:   Sun, 6 Aug 2017 21:57:13 +0400
From:   Ilya Matveychikov <matvejchikov@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH] tcp_input: move out condition check from tcp_data_queue()


> On Aug 6, 2017, at 9:07 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> 
> On Sun, 2017-08-06 at 13:51 +0400, Ilya Matveychikov wrote:
>> As tcp_data_queue() function is used just only twice it's better
>> to move out the first check and wrap it with inline. It saves a
>> single call in case the condition evaluated as true.
>> 
>> Signed-off-by: Ilya V. Matveychikov <matvejchikov@...il.com>
>> ---
>> net/ipv4/tcp_input.c | 14 +++++++++-----
>> 1 file changed, 9 insertions(+), 5 deletions(-)
>> 
>> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
>> index 2920e0c..141a722 100644
>> --- a/net/ipv4/tcp_input.c
>> +++ b/net/ipv4/tcp_input.c
>> @@ -4585,16 +4585,12 @@ int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
>> 
>> }
>> 
>> -static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
>> +static void __tcp_data_queue(struct sock *sk, struct sk_buff *skb)
>> {
>> 	struct tcp_sock *tp = tcp_sk(sk);
>> 	bool fragstolen = false;
>> 	int eaten = -1;
>> 
>> -	if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
>> -		__kfree_skb(skb);
>> -		return;
>> -	}
>> 	skb_dst_drop(skb);
>> 	__skb_pull(skb, tcp_hdr(skb)->doff * 4);
>> 
>> @@ -4703,6 +4699,14 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
>> 	tcp_data_queue_ofo(sk, skb);
>> }
>> 
>> +static inline void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
>> +{
>> +	if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
>> +		__kfree_skb(skb);
>> +	else
>> +		__tcp_data_queue(sk, skb);
>> +}
>> +
> 
> We wont accept such a change, because this code does not need to be
> inlined in the callers, ( and btw inline in .c files are discouraged
> these days )

Not sure that I understand you point. What’s the reason for that code
not need to be inlined in the callers?