From d5fb143dbe8d3050c9abcd390d65928e2a3e646e Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 27 Jan 2026 03:21:47 +0000 Subject: [PATCH] tcp: move tcp_rack_advance() to tcp_input.c tcp_rack_advance() is called from tcp_ack() and tcp_sacktag_one(). Moving it to tcp_input.c allows the compiler to inline it and save both space and cpu cycles in TCP fast path. $ scripts/bloat-o-meter -t vmlinux.1 vmlinux.2 add/remove: 0/2 grow/shrink: 1/1 up/down: 98/-132 (-34) Function old new delta tcp_ack 5741 5839 +98 tcp_sacktag_one 407 395 -12 __pfx_tcp_rack_advance 16 - -16 tcp_rack_advance 104 - -104 Total: Before=22572680, After=22572646, chg -0.00% Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260127032147.3498272-4-edumazet@google.com Signed-off-by: Jakub Kicinski --- include/net/tcp.h | 2 -- net/ipv4/tcp_input.c | 32 ++++++++++++++++++++++++++++++++ net/ipv4/tcp_recovery.c | 32 -------------------------------- 3 files changed, 32 insertions(+), 34 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index a4d9f263ea68..f1cf9e6730c8 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -2514,8 +2514,6 @@ void tcp_newreno_mark_lost(struct sock *sk, bool snd_una_advanced); extern s32 tcp_rack_skb_timeout(struct tcp_sock *tp, struct sk_buff *skb, u32 reo_wnd); extern bool tcp_rack_mark_lost(struct sock *sk); -extern void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq, - u64 xmit_time); extern void tcp_rack_reo_timeout(struct sock *sk); /* tcp_plb.c */ diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index d504a9a9b6ec..a2a872382fc0 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1558,6 +1558,38 @@ static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, return in_sack; } +/* Record the most recently (re)sent time among the (s)acked packets + * This is "Step 3: Advance RACK.xmit_time and update RACK.RTT" from + * draft-cheng-tcpm-rack-00.txt + */ +static void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, + u32 end_seq, u64 xmit_time) +{ + u32 rtt_us; + + rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, xmit_time); + if (rtt_us < tcp_min_rtt(tp) && (sacked & TCPCB_RETRANS)) { + /* If the sacked packet was retransmitted, it's ambiguous + * whether the retransmission or the original (or the prior + * retransmission) was sacked. + * + * If the original is lost, there is no ambiguity. Otherwise + * we assume the original can be delayed up to aRTT + min_rtt. + * the aRTT term is bounded by the fast recovery or timeout, + * so it's at least one RTT (i.e., retransmission is at least + * an RTT later). + */ + return; + } + tp->rack.advanced = 1; + tp->rack.rtt_us = rtt_us; + if (tcp_skb_sent_after(xmit_time, tp->rack.mstamp, + end_seq, tp->rack.end_seq)) { + tp->rack.mstamp = xmit_time; + tp->rack.end_seq = end_seq; + } +} + /* Mark the given newly-SACKed range as such, adjusting counters and hints. */ static u8 tcp_sacktag_one(struct sock *sk, struct tcp_sacktag_state *state, u8 sacked, diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c index 40732b84771e..139646751073 100644 --- a/net/ipv4/tcp_recovery.c +++ b/net/ipv4/tcp_recovery.c @@ -111,38 +111,6 @@ bool tcp_rack_mark_lost(struct sock *sk) return !!timeout; } -/* Record the most recently (re)sent time among the (s)acked packets - * This is "Step 3: Advance RACK.xmit_time and update RACK.RTT" from - * draft-cheng-tcpm-rack-00.txt - */ -void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq, - u64 xmit_time) -{ - u32 rtt_us; - - rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, xmit_time); - if (rtt_us < tcp_min_rtt(tp) && (sacked & TCPCB_RETRANS)) { - /* If the sacked packet was retransmitted, it's ambiguous - * whether the retransmission or the original (or the prior - * retransmission) was sacked. - * - * If the original is lost, there is no ambiguity. Otherwise - * we assume the original can be delayed up to aRTT + min_rtt. - * the aRTT term is bounded by the fast recovery or timeout, - * so it's at least one RTT (i.e., retransmission is at least - * an RTT later). - */ - return; - } - tp->rack.advanced = 1; - tp->rack.rtt_us = rtt_us; - if (tcp_skb_sent_after(xmit_time, tp->rack.mstamp, - end_seq, tp->rack.end_seq)) { - tp->rack.mstamp = xmit_time; - tp->rack.end_seq = end_seq; - } -} - /* We have waited long enough to accommodate reordering. Mark the expired * packets lost and retransmit them. */ -- 2.47.3