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Commit 5e13a0d3 authored by Yafang Shao's avatar Yafang Shao Committed by David S. Miller
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tcp: minor optimization in tcp ack fast path processing 



Bitwise operation is a little faster.
So I replace after() with using the flag FLAG_SND_UNA_ADVANCED as it is
already set before.

In addtion, there's another similar improvement in tcp_cwnd_reduction().

Cc: Joe Perches <joe@perches.com>
Suggested-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarYafang Shao <laoar.shao@gmail.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0cf3a68a

net/ipv4/tcp_input.c

+4 −3
Original line number Diff line number Diff line
@@ -2457,8 +2457,8 @@ void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int flag) 
		u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered +

			       tp->prior_cwnd - 1;

		sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out;

	} else if ((flag & FLAG_RETRANS_DATA_ACKED) &&

		   !(flag & FLAG_LOST_RETRANS)) {

	} else if ((flag & (FLAG_RETRANS_DATA_ACKED | FLAG_LOST_RETRANS)) ==

		   FLAG_RETRANS_DATA_ACKED) {

		sndcnt = min_t(int, delta,

			       max_t(int, tp->prr_delivered - tp->prr_out,

				     newly_acked_sacked) + 1);
@@ -3610,7 +3610,8 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) 
	if (flag & FLAG_UPDATE_TS_RECENT)

		tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);



	if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) {

	if ((flag & (FLAG_SLOWPATH | FLAG_SND_UNA_ADVANCED)) ==

	    FLAG_SND_UNA_ADVANCED) {

		/* Window is constant, pure forward advance.

		 * No more checks are required.

		 * Note, we use the fact that SND.UNA>=SND.WL2.