diff options
| author | Eric Dumazet <edumazet@google.com> | 2026-03-23 23:49:20 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-03-24 21:00:38 -0700 |
| commit | d1e59a46973719e458bec78d00dd767d7a7ba71f (patch) | |
| tree | 43fa8dcafd5334b6373a93d77d56ee0f2a1e464f /include | |
| parent | 112f4c6320070b19e7d49cba758400adc279e377 (diff) | |
tcp: add cwnd_event_tx_start to tcp_congestion_ops
(tcp_congestion_ops)->cwnd_event() is called very often, with
@event oscillating between CA_EVENT_TX_START and other values.
This is not branch prediction friendly.
Provide a new cwnd_event_tx_start pointer dedicated for CA_EVENT_TX_START.
Both BBR and CUBIC benefit from this change, since they only care
about CA_EVENT_TX_START.
No change in kernel size:
$ scripts/bloat-o-meter -t vmlinux.0 vmlinux
add/remove: 4/4 grow/shrink: 3/1 up/down: 564/-568 (-4)
Function old new delta
bbr_cwnd_event_tx_start - 450 +450
cubictcp_cwnd_event_tx_start - 70 +70
__pfx_cubictcp_cwnd_event_tx_start - 16 +16
__pfx_bbr_cwnd_event_tx_start - 16 +16
tcp_unregister_congestion_control 93 99 +6
tcp_update_congestion_control 518 521 +3
tcp_register_congestion_control 422 425 +3
__tcp_transmit_skb 3308 3306 -2
__pfx_cubictcp_cwnd_event 16 - -16
__pfx_bbr_cwnd_event 16 - -16
cubictcp_cwnd_event 80 - -80
bbr_cwnd_event 454 - -454
Total: Before=25240512, After=25240508, chg -0.00%
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260323234920.1097858-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/tcp.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index f87bdacb5a69..39ff4cf3c810 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1341,6 +1341,9 @@ struct tcp_congestion_ops { /* call when cwnd event occurs (optional) */ void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev); + /* call when CA_EVENT_TX_START cwnd event occurs (optional) */ + void (*cwnd_event_tx_start)(struct sock *sk); + /* call when ack arrives (optional) */ void (*in_ack_event)(struct sock *sk, u32 flags); @@ -1440,6 +1443,11 @@ static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event) { const struct inet_connection_sock *icsk = inet_csk(sk); + if (event == CA_EVENT_TX_START) { + if (icsk->icsk_ca_ops->cwnd_event_tx_start) + icsk->icsk_ca_ops->cwnd_event_tx_start(sk); + return; + } if (icsk->icsk_ca_ops->cwnd_event) icsk->icsk_ca_ops->cwnd_event(sk, event); } |