Re: [PATCH/RFC] [v2] TCP: use non-delayed ACK for congestion control RTT
From: Gavin McCullagh <hidden>
Date: 2007-12-18 20:40:19
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
The last attempt didn't take account of the situation where a timestamp wasn't available and tcp_clean_rtx_queue() has to feed both the RTO and the congestion avoidance. This updated patch stores both RTTs, making the delayed one available for the RTO and the other (ca_seq_rtt) available for congestion control. Signed-off-by: Gavin McCullagh <redacted>
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 889c893..6fb7989 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c@@ -2651,6 +2651,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p, u32 cnt = 0; u32 reord = tp->packets_out; s32 seq_rtt = -1; + s32 ca_seq_rtt = -1; ktime_t last_ackt = net_invalid_timestamp(); while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
@@ -2686,13 +2687,15 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p, if (sacked & TCPCB_SACKED_RETRANS) tp->retrans_out -= packets_acked; flag |= FLAG_RETRANS_DATA_ACKED; + ca_seq_rtt = -1; seq_rtt = -1; if ((flag & FLAG_DATA_ACKED) || (packets_acked > 1)) flag |= FLAG_NONHEAD_RETRANS_ACKED; } else { + ca_seq_rtt = now - scb->when; if (seq_rtt < 0) { - seq_rtt = now - scb->when; + seq_rtt = ca_seq_rtt; if (fully_acked) last_ackt = skb->tstamp; }
@@ -2709,8 +2712,9 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p, !before(end_seq, tp->snd_up)) tp->urg_mode = 0; } else { + ca_seq_rtt = now - scb->when; if (seq_rtt < 0) { - seq_rtt = now - scb->when; + seq_rtt = ca_seq_rtt; if (fully_acked) last_ackt = skb->tstamp; }
@@ -2772,8 +2776,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p, net_invalid_timestamp())) rtt_us = ktime_us_delta(ktime_get_real(), last_ackt); - else if (seq_rtt > 0) - rtt_us = jiffies_to_usecs(seq_rtt); + else if (ca_seq_rtt > 0) + rtt_us = jiffies_to_usecs(ca_seq_rtt); } ca_ops->pkts_acked(sk, pkts_acked, rtt_us);