quiche/recovery/gcongestion/bbr2/
probe_rtt.rs

1// Copyright (c) 2015 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5// Copyright (C) 2023, Cloudflare, Inc.
6// All rights reserved.
7//
8// Redistribution and use in source and binary forms, with or without
9// modification, are permitted provided that the following conditions are
10// met:
11//
12//     * Redistributions of source code must retain the above copyright notice,
13//       this list of conditions and the following disclaimer.
14//
15//     * Redistributions in binary form must reproduce the above copyright
16//       notice, this list of conditions and the following disclaimer in the
17//       documentation and/or other materials provided with the distribution.
18//
19// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
20// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
21// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
23// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
24// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
25// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
26// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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30
31use std::time::Instant;
32
33use crate::recovery::gcongestion::Acked;
34use crate::recovery::gcongestion::Lost;
35
36use super::mode::Cycle;
37use super::mode::Mode;
38use super::mode::ModeImpl;
39use super::network_model::BBRv2NetworkModel;
40use super::BBRv2CongestionEvent;
41use super::Limits;
42use super::PARAMS;
43
44#[derive(Debug)]
45pub(super) struct ProbeRTT {
46    pub(super) model: BBRv2NetworkModel,
47    pub(super) cycle: Cycle,
48    exit_time: Option<Instant>,
49}
50
51impl ProbeRTT {
52    pub(super) fn new(model: BBRv2NetworkModel, cycle: Cycle) -> Self {
53        ProbeRTT {
54            model,
55            cycle,
56            exit_time: None,
57        }
58    }
59
60    fn into_probe_bw(
61        mut self, now: Instant, congestion_event: Option<&BBRv2CongestionEvent>,
62    ) -> Mode {
63        self.leave(now, congestion_event);
64        let mut next_mode = Mode::probe_bw(self.model, self.cycle);
65        next_mode.enter(now, congestion_event);
66        next_mode
67    }
68
69    fn inflight_target(&self) -> usize {
70        self.model.bdp(
71            self.model.max_bandwidth(),
72            PARAMS.probe_rtt_inflight_target_bdp_fraction,
73        )
74    }
75}
76
77impl ModeImpl for ProbeRTT {
78    fn is_probing_for_bandwidth(&self) -> bool {
79        false
80    }
81
82    fn on_congestion_event(
83        mut self, _prior_in_flight: usize, event_time: Instant,
84        _acked_packets: &[Acked], _lost_packets: &[Lost],
85        congestion_event: &mut BBRv2CongestionEvent,
86        _target_bytes_inflight: usize,
87    ) -> Mode {
88        match self.exit_time {
89            None => {
90                if congestion_event.bytes_in_flight <= self.inflight_target() {
91                    self.exit_time = Some(
92                        congestion_event.event_time + PARAMS.probe_rtt_duration,
93                    )
94                }
95                Mode::ProbeRTT(self)
96            },
97            Some(exit_time) =>
98                if congestion_event.event_time > exit_time {
99                    self.into_probe_bw(event_time, Some(congestion_event))
100                } else {
101                    Mode::ProbeRTT(self)
102                },
103        }
104    }
105
106    fn get_cwnd_limits(&self) -> Limits<usize> {
107        let inflight_upper_bound = self
108            .model
109            .inflight_lo()
110            .min(self.model.inflight_hi_with_headroom());
111        Limits::no_greater_than(inflight_upper_bound.min(self.inflight_target()))
112    }
113
114    fn on_exit_quiescence(
115        self, now: Instant, _quiescence_start_time: Instant,
116    ) -> Mode {
117        match self.exit_time {
118            None => self.into_probe_bw(now, None),
119            Some(exit_time) if now > exit_time => self.into_probe_bw(now, None),
120            Some(_) => Mode::ProbeRTT(self),
121        }
122    }
123
124    fn enter(
125        &mut self, _now: Instant,
126        _congestion_event: Option<&BBRv2CongestionEvent>,
127    ) {
128        self.model.set_pacing_gain(1.0);
129        self.model.set_cwnd_gain(1.0);
130        self.exit_time = None;
131    }
132
133    fn leave(
134        &mut self, _now: Instant,
135        _congestion_event: Option<&BBRv2CongestionEvent>,
136    ) {
137    }
138}
quiche/recovery/gcongestion/bbr2/probe_rtt.rs

quiche/recovery/gcongestion/bbr2/
probe_rtt.rs
