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d1e59a4697
(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>