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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: Eric Dumazet <edumazet@google.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yafang Shao 2018-11-11 20:10:10 +08:00 committed by David S. Miller
parent 0cf3a68a53
commit 5e13a0d3f5
1 changed files with 4 additions and 3 deletions
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7
net/ipv4/tcp_input.c
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@ -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 + u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered +
tp->prior_cwnd - 1; tp->prior_cwnd - 1;
sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out; sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out;
} else if ((flag & FLAG_RETRANS_DATA_ACKED) && } else if ((flag & (FLAG_RETRANS_DATA_ACKED | FLAG_LOST_RETRANS)) ==
!(flag & FLAG_LOST_RETRANS)) { FLAG_RETRANS_DATA_ACKED) {
sndcnt = min_t(int, delta, sndcnt = min_t(int, delta,
max_t(int, tp->prr_delivered - tp->prr_out, max_t(int, tp->prr_delivered - tp->prr_out,
newly_acked_sacked) + 1); 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) if (flag & FLAG_UPDATE_TS_RECENT)
tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 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. /* Window is constant, pure forward advance.
* No more checks are required. * No more checks are required.
* Note, we use the fact that SND.UNA>=SND.WL2. * Note, we use the fact that SND.UNA>=SND.WL2.