tcp: remove pointless .dsack/.num_sacks code (5861f8e5) · Commits · 戴 / test

In the pure assignment case, the earlier zeroing is still in effect. David S. Miller raised concerns if the ifs are there to avoid dirtying cachelines. I came to these conclusions: > We'll be dirty it anyway (now that I check), the first "real" statement > in tcp_rcv_established is: > > tp->rx_opt.saw_tstamp = 0; > > ...that'll land on the same dword. :-/ > > I suppose the blocks are there just because they had more complexity > inside when they had to calculate the eff_sacks too (maybe it would > have been better to just remove them in that drop-patch so you would > have had less head-ache :-)). Signed-off-by:

Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

+2 −5

Original line number	Diff line number	Diff line
		@@ -4248,7 +4248,6 @@ static void tcp_sack_remove(struct tcp_sock *tp)
		this_sack++;
		sp++;
		}
		if (num_sacks != tp->rx_opt.num_sacks)
		tp->rx_opt.num_sacks = num_sacks;
		}

		@@ -4325,7 +4324,6 @@ static void tcp_data_queue(struct sock sk, struct sk_buff skb)

		TCP_ECN_accept_cwr(tp, skb);

		if (tp->rx_opt.dsack)
		tp->rx_opt.dsack = 0;

		/* Queue data for delivery to the user.
		@@ -4445,7 +4443,6 @@ drop:
		/* Initial out of order segment, build 1 SACK. */
		if (tcp_is_sack(tp)) {
		tp->rx_opt.num_sacks = 1;
		tp->rx_opt.dsack = 0;
		tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
		tp->selective_acks[0].end_seq =
		TCP_SKB_CB(skb)->end_seq;

net/ipv4/tcp_output.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -441,7 +441,6 @@ static void tcp_options_write(__be32 ptr, struct tcp_sock tp,
		*ptr++ = htonl(sp[this_sack].end_seq);
		}

		if (tp->rx_opt.dsack)
		tp->rx_opt.dsack = 0;
		}
		}

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