Commit 473900a5 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2bbc078f

net/ipv4/tcp_cubic.c

+3 −6
Original line number Diff line number Diff line
@@ -381,9 +381,6 @@ static void hystart_update(struct sock *sk, u32 delay) 
	struct tcp_sock *tp = tcp_sk(sk);

	struct bictcp *ca = inet_csk_ca(sk);



	if (ca->found & hystart_detect)

		return;



	if (hystart_detect & HYSTART_ACK_TRAIN) {

		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) {

			ca->last_ack = now;

			if ((s32)(now - ca->round_start) > ca->delay_min >> 4) {

				ca->found |= HYSTART_ACK_TRAIN;

				ca->found = 1;

				NET_INC_STATS(sock_net(sk),

					      LINUX_MIB_TCPHYSTARTTRAINDETECT);

				NET_ADD_STATS(sock_net(sk),
@@ -412,7 +409,7 @@ static void hystart_update(struct sock *sk, u32 delay) 
		} else {

			if (ca->curr_rtt > ca->delay_min +

			    HYSTART_DELAY_THRESH(ca->delay_min >> 3)) {

				ca->found |= HYSTART_DELAY;

				ca->found = 1;

				NET_INC_STATS(sock_net(sk),

					      LINUX_MIB_TCPHYSTARTDELAYDETECT);

				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;



	/* 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)

		hystart_update(sk, delay);

}

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