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1// SPDX-License-Identifier: GPL-2.02// Test of slow start when not application-limited, so that3// the cwnd continues to grow, even if TSQ triggers.4// In this variant, the receiver ACKs every other packet,5// approximating standard delayed ACKs.6 7// Note we use FQ/pacing to check if TCP Small Queues is not hurting8 9`./defaults.sh10tc qdisc replace dev tun0 root fq11sysctl -q net/ipv4/tcp_pacing_ss_ratio=20012sysctl -e -q net.ipv4.tcp_min_tso_segs=2`13 14 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 315 +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 016 +0 bind(3, ..., ...) = 017 +0 listen(3, 1) = 018 19 +.1 < S 0:0(0) win 32792 <mss 1460,sackOK,nop,nop,nop,wscale 7>20 +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>21 +.1 < . 1:1(0) ack 1 win 50022 +0 accept(3, ..., ...) = 423 +0 setsockopt(4, SOL_SOCKET, SO_SNDBUF, [200000], 4) = 024 25 +0 write(4, ..., 40000) = 4000026// This might change if we cook the initial packet with 10 MSS.27 +0 > P. 1:2921(2920) ack 128 +0 > P. 2921:5841(2920) ack 129 +0 > P. 5841:8761(2920) ack 130 +0 > P. 8761:11681(2920) ack 131 +0 > P. 11681:14601(2920) ack 132 +0 %{ assert tcpi_snd_cwnd == 10, tcpi_snd_cwnd }%33 34+.105 < . 1:1(0) ack 2921 win 50035 +0 %{ assert tcpi_snd_cwnd == 12, tcpi_snd_cwnd }%36 37// Note: after this commit : "net_sched: sch_fq: account for schedule/timers drifts"38// FQ notices that this packet missed the 'time to send next packet' computed39// when prior packet (11681:14601(2920)) was sent.40// So FQ will allow following packet to be sent a bit earlier (quantum/2)41// (FQ commit allows an application/cwnd limited flow to get at most quantum/2 extra credit)42 +0 > P. 14601:17521(2920) ack 143 44+.003 < . 1:1(0) ack 5841 win 50045 +0 %{ assert tcpi_snd_cwnd == 14, tcpi_snd_cwnd }%46 47+.001 > P. 17521:20441(2920) ack 148 49+.001 < . 1:1(0) ack 8761 win 50050 +0 %{ assert tcpi_snd_cwnd == 16, tcpi_snd_cwnd }%51 52// remaining packets are delivered at a constant rate.53+.007 > P. 20441:23361(2920) ack 154 55+.002 < . 1:1(0) ack 11681 win 50056 +0 %{ assert tcpi_snd_cwnd == 18, tcpi_snd_cwnd }%57+.001 < . 1:1(0) ack 14601 win 50058 59+.004 > P. 23361:26281(2920) ack 160 61+.007 > P. 26281:29201(2920) ack 162 63 +0 %{ assert tcpi_snd_cwnd == 20, 'cwnd=%d' % tcpi_snd_cwnd }%64