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tcp_cubic: optimize hystart_update() 

We do not care which bit in ca->found is set.

We avoid accessing hystart and hystart_detect unless really needed,
possibly avoiding one cache line miss.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2019-12-23 12:27:50 -08:00 committed by David S. Miller
parent 2bbc078f81
commit 473900a504
1 changed files with 3 additions and 6 deletions
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9
net/ipv4/tcp_cubic.c
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@ -381,9 +381,6 @@ static void hystart_update(struct sock *sk, u32 delay)
struct tcp_sock *tp = tcp_sk(sk); struct tcp_sock *tp = tcp_sk(sk);
struct bictcp *ca = inet_csk_ca(sk); struct bictcp *ca = inet_csk_ca(sk);
if (ca->found & hystart_detect)
return;
if (hystart_detect & HYSTART_ACK_TRAIN) { if (hystart_detect & HYSTART_ACK_TRAIN) {
u32 now = bictcp_clock(); u32 now = bictcp_clock();
@ -391,7 +388,7 @@ static void hystart_update(struct sock *sk, u32 delay)
if ((s32)(now - ca->last_ack) <= hystart_ack_delta) { if ((s32)(now - ca->last_ack) <= hystart_ack_delta) {
ca->last_ack = now; ca->last_ack = now;
if ((s32)(now - ca->round_start) > ca->delay_min >> 4) { if ((s32)(now - ca->round_start) > ca->delay_min >> 4) {
ca->found |= HYSTART_ACK_TRAIN; ca->found = 1;
NET_INC_STATS(sock_net(sk), NET_INC_STATS(sock_net(sk),
LINUX_MIB_TCPHYSTARTTRAINDETECT); LINUX_MIB_TCPHYSTARTTRAINDETECT);
NET_ADD_STATS(sock_net(sk), NET_ADD_STATS(sock_net(sk),
@ -412,7 +409,7 @@ static void hystart_update(struct sock *sk, u32 delay)
} else { } else {
if (ca->curr_rtt > ca->delay_min + if (ca->curr_rtt > ca->delay_min +
HYSTART_DELAY_THRESH(ca->delay_min >> 3)) { HYSTART_DELAY_THRESH(ca->delay_min >> 3)) {
ca->found |= HYSTART_DELAY; ca->found = 1;
NET_INC_STATS(sock_net(sk), NET_INC_STATS(sock_net(sk),
LINUX_MIB_TCPHYSTARTDELAYDETECT); LINUX_MIB_TCPHYSTARTDELAYDETECT);
NET_ADD_STATS(sock_net(sk), NET_ADD_STATS(sock_net(sk),
@ -450,7 +447,7 @@ static void bictcp_acked(struct sock *sk, const struct ack_sample *sample)
ca->delay_min = delay; ca->delay_min = delay;
/* hystart triggers when cwnd is larger than some threshold */ /* hystart triggers when cwnd is larger than some threshold */
if (hystart && tcp_in_slow_start(tp) && if (!ca->found && hystart && tcp_in_slow_start(tp) &&
tp->snd_cwnd >= hystart_low_window) tp->snd_cwnd >= hystart_low_window)
hystart_update(sk, delay); hystart_update(sk, delay);
} }