netdev - Re: [PATCH net-next] tcp: minor optimizations around tcp

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Message-Id: <20160516.134720.895829616600822039.davem@davemloft.net>
Date:	Mon, 16 May 2016 13:47:20 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next] tcp: minor optimizations around tcp_hdr()
 usage

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 13 May 2016 09:16:40 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> tcp_hdr() is slightly more expensive than using skb->data in contexts
> where we know they point to the same byte.
> 
> In receive path, tcp_v4_rcv() and tcp_v6_rcv() are in this situation,
> as tcp header has not been pulled yet.
> 
> In output path, the same can be said when we just pushed the tcp header
> in the skb, in tcp_transmit_skb() and tcp_make_synack()
> 
> Also factorize the two checks for tcb->tcp_flags & TCPHDR_SYN in
> tcp_transmit_skb() and pass tcp header pointer to tcp_ecn_send(),
> so that compiler can further optimize and avoid a reload.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied.