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tcp: move tcp_rack_update_reo_wnd() to tcp_input.c

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tcp_rack_update_reo_wnd() is called only once from tcp_ack()

Move it to tcp_input.c so that it can be inlined by the compiler
to save space and cpu cycles.

$ scripts/bloat-o-meter -t vmlinux.old vmlinux.new
add/remove: 0/2 grow/shrink: 1/0 up/down: 110/-153 (-43)
Function                                     old     new   delta
tcp_ack                                     5631    5741    +110
__pfx_tcp_rack_update_reo_wnd                 16       -     -16
tcp_rack_update_reo_wnd                      137       -    -137
Total: Before=22572723, After=22572680, chg -0.00%

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260127032147.3498272-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-01-27 03:21:46 +00:00 committed by Jakub Kicinski
parent 773a700213
commit 629a68865a
3 changed files with 43 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/net/tcp.h
View File

@ -2517,7 +2517,6 @@ 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);
extern void tcp_rack_update_reo_wnd(struct sock *sk, struct rate_sample *rs);
/* tcp_plb.c */

43
net/ipv4/tcp_input.c
View File

@ -4149,6 +4149,49 @@ static u32 tcp_newly_delivered(struct sock *sk, u32 prior_delivered,
return delivered;
}
/* Updates the RACK's reo_wnd based on DSACK and no. of recoveries.
*
* If a DSACK is received that seems like it may have been due to reordering
* triggering fast recovery, increment reo_wnd by min_rtt/4 (upper bounded
* by srtt), since there is possibility that spurious retransmission was
* due to reordering delay longer than reo_wnd.
*
* Persist the current reo_wnd value for TCP_RACK_RECOVERY_THRESH (16)
* no. of successful recoveries (accounts for full DSACK-based loss
* recovery undo). After that, reset it to default (min_rtt/4).
*
* At max, reo_wnd is incremented only once per rtt. So that the new
* DSACK on which we are reacting, is due to the spurious retx (approx)
* after the reo_wnd has been updated last time.
*
* reo_wnd is tracked in terms of steps (of min_rtt/4), rather than
* absolute value to account for change in rtt.
*/
static void tcp_rack_update_reo_wnd(struct sock *sk, struct rate_sample *rs)
{
struct tcp_sock *tp = tcp_sk(sk);
if ((READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) &
TCP_RACK_STATIC_REO_WND) ||
!rs->prior_delivered)
return;
/* Disregard DSACK if a rtt has not passed since we adjusted reo_wnd */
if (before(rs->prior_delivered, tp->rack.last_delivered))
tp->rack.dsack_seen = 0;
/* Adjust the reo_wnd if update is pending */
if (tp->rack.dsack_seen) {
tp->rack.reo_wnd_steps = min_t(u32, 0xFF,
tp->rack.reo_wnd_steps + 1);
tp->rack.dsack_seen = 0;
tp->rack.last_delivered = tp->delivered;
tp->rack.reo_wnd_persist = TCP_RACK_RECOVERY_THRESH;
} else if (!tp->rack.reo_wnd_persist) {
tp->rack.reo_wnd_steps = 1;
}
}
/* This routine deals with incoming acks, but not outgoing ones. */
static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
{

43
net/ipv4/tcp_recovery.c
View File

@ -166,49 +166,6 @@ void tcp_rack_reo_timeout(struct sock *sk)
tcp_rearm_rto(sk);
}
/* Updates the RACK's reo_wnd based on DSACK and no. of recoveries.
*
* If a DSACK is received that seems like it may have been due to reordering
* triggering fast recovery, increment reo_wnd by min_rtt/4 (upper bounded
* by srtt), since there is possibility that spurious retransmission was
* due to reordering delay longer than reo_wnd.
*
* Persist the current reo_wnd value for TCP_RACK_RECOVERY_THRESH (16)
* no. of successful recoveries (accounts for full DSACK-based loss
* recovery undo). After that, reset it to default (min_rtt/4).
*
* At max, reo_wnd is incremented only once per rtt. So that the new
* DSACK on which we are reacting, is due to the spurious retx (approx)
* after the reo_wnd has been updated last time.
*
* reo_wnd is tracked in terms of steps (of min_rtt/4), rather than
* absolute value to account for change in rtt.
*/
void tcp_rack_update_reo_wnd(struct sock *sk, struct rate_sample *rs)
{
struct tcp_sock *tp = tcp_sk(sk);
if ((READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) &
TCP_RACK_STATIC_REO_WND) ||
!rs->prior_delivered)
return;
/* Disregard DSACK if a rtt has not passed since we adjusted reo_wnd */
if (before(rs->prior_delivered, tp->rack.last_delivered))
tp->rack.dsack_seen = 0;
/* Adjust the reo_wnd if update is pending */
if (tp->rack.dsack_seen) {
tp->rack.reo_wnd_steps = min_t(u32, 0xFF,
tp->rack.reo_wnd_steps + 1);
tp->rack.dsack_seen = 0;
tp->rack.last_delivered = tp->delivered;
tp->rack.reo_wnd_persist = TCP_RACK_RECOVERY_THRESH;
} else if (!tp->rack.reo_wnd_persist) {
tp->rack.reo_wnd_steps = 1;
}
}
/* RFC6582 NewReno recovery for non-SACK connection. It simply retransmits
* the next unacked packet upon receiving
* a) three or more DUPACKs to start the fast recovery