1// Copyright 2014 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#include "net/quic/congestion_control/rtt_stats.h"
6
7#include "base/logging.h"
8#include "testing/gtest/include/gtest/gtest.h"
9
10namespace net {
11namespace test {
12
13class RttStatsPeer {
14 public:
15  static QuicTime::Delta GetHalfWindowRtt(const RttStats* rtt_stats) {
16    return rtt_stats->half_window_rtt_.rtt;
17  }
18
19  static QuicTime::Delta GetQuarterWindowRtt(const RttStats* rtt_stats) {
20    return rtt_stats->quarter_window_rtt_.rtt;
21  }
22};
23
24class RttStatsTest : public ::testing::Test {
25 protected:
26  RttStats rtt_stats_;
27};
28
29TEST_F(RttStatsTest, MinRtt) {
30  rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(100),
31                       QuicTime::Delta::Zero(),
32                       QuicTime::Zero());
33  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(100), rtt_stats_.min_rtt());
34  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(100),
35            rtt_stats_.recent_min_rtt());
36  rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(10),
37                       QuicTime::Delta::Zero(),
38                       QuicTime::Zero().Add(
39                           QuicTime::Delta::FromMilliseconds(10)));
40  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.min_rtt());
41  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.recent_min_rtt());
42  rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(50),
43                       QuicTime::Delta::Zero(),
44                       QuicTime::Zero().Add(
45                           QuicTime::Delta::FromMilliseconds(20)));
46  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.min_rtt());
47  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.recent_min_rtt());
48  rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(50),
49                       QuicTime::Delta::Zero(),
50                       QuicTime::Zero().Add(
51                           QuicTime::Delta::FromMilliseconds(30)));
52  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.min_rtt());
53  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.recent_min_rtt());
54  rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(50),
55                       QuicTime::Delta::Zero(),
56                       QuicTime::Zero().Add(
57                           QuicTime::Delta::FromMilliseconds(40)));
58  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.min_rtt());
59  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.recent_min_rtt());
60}
61
62TEST_F(RttStatsTest, RecentMinRtt) {
63  rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(10),
64                       QuicTime::Delta::Zero(),
65                       QuicTime::Zero());
66  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.min_rtt());
67  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.recent_min_rtt());
68
69  rtt_stats_.SampleNewRecentMinRtt(4);
70  for (int i = 0; i < 3; ++i) {
71    rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(50),
72                       QuicTime::Delta::Zero(),
73                       QuicTime::Zero());
74    EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.min_rtt());
75    EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10),
76              rtt_stats_.recent_min_rtt());
77  }
78  rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(50),
79                        QuicTime::Delta::Zero(),
80                        QuicTime::Zero());
81  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.min_rtt());
82  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(50), rtt_stats_.recent_min_rtt());
83}
84
85TEST_F(RttStatsTest, WindowedRecentMinRtt) {
86  // Set the window to 99ms, so 25ms is more than a quarter rtt.
87  rtt_stats_.set_recent_min_rtt_window(QuicTime::Delta::FromMilliseconds(99));
88
89  QuicTime now = QuicTime::Zero();
90  QuicTime::Delta rtt_sample = QuicTime::Delta::FromMilliseconds(10);
91  rtt_stats_.UpdateRtt(rtt_sample, QuicTime::Delta::Zero(), now);
92  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.min_rtt());
93  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.recent_min_rtt());
94
95  // Gradually increase the rtt samples and ensure the recent_min_rtt starts
96  // rising.
97  for (int i = 0; i < 8; ++i) {
98    now = now.Add(QuicTime::Delta::FromMilliseconds(25));
99    rtt_sample = rtt_sample.Add(QuicTime::Delta::FromMilliseconds(10));
100    rtt_stats_.UpdateRtt(rtt_sample, QuicTime::Delta::Zero(), now);
101    EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.min_rtt());
102    EXPECT_EQ(rtt_sample, RttStatsPeer::GetQuarterWindowRtt(&rtt_stats_));
103    EXPECT_EQ(rtt_sample.Subtract(QuicTime::Delta::FromMilliseconds(10)),
104              RttStatsPeer::GetHalfWindowRtt(&rtt_stats_));
105    if (i < 3) {
106      EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10),
107                rtt_stats_.recent_min_rtt());
108    } else if (i < 5) {
109      EXPECT_EQ(QuicTime::Delta::FromMilliseconds(30),
110                rtt_stats_.recent_min_rtt());
111    } else if (i < 7) {
112      EXPECT_EQ(QuicTime::Delta::FromMilliseconds(50),
113                rtt_stats_.recent_min_rtt());
114    } else {
115      EXPECT_EQ(QuicTime::Delta::FromMilliseconds(70),
116                rtt_stats_.recent_min_rtt());
117    }
118  }
119
120  // A new quarter rtt low sets that, but nothing else.
121  rtt_sample = rtt_sample.Subtract(QuicTime::Delta::FromMilliseconds(5));
122  rtt_stats_.UpdateRtt(rtt_sample, QuicTime::Delta::Zero(), now);
123  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.min_rtt());
124  EXPECT_EQ(rtt_sample, RttStatsPeer::GetQuarterWindowRtt(&rtt_stats_));
125  EXPECT_EQ(rtt_sample.Subtract(QuicTime::Delta::FromMilliseconds(5)),
126            RttStatsPeer::GetHalfWindowRtt(&rtt_stats_));
127  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(70),
128            rtt_stats_.recent_min_rtt());
129
130  // A new half rtt low sets that and the quarter rtt low.
131  rtt_sample = rtt_sample.Subtract(QuicTime::Delta::FromMilliseconds(15));
132  rtt_stats_.UpdateRtt(rtt_sample, QuicTime::Delta::Zero(), now);
133  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.min_rtt());
134  EXPECT_EQ(rtt_sample, RttStatsPeer::GetQuarterWindowRtt(&rtt_stats_));
135  EXPECT_EQ(rtt_sample, RttStatsPeer::GetHalfWindowRtt(&rtt_stats_));
136  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(70),
137            rtt_stats_.recent_min_rtt());
138
139  // A new full window loss sets the recent_min_rtt, but not min_rtt.
140  rtt_sample = QuicTime::Delta::FromMilliseconds(65);
141  rtt_stats_.UpdateRtt(rtt_sample, QuicTime::Delta::Zero(), now);
142  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(10), rtt_stats_.min_rtt());
143  EXPECT_EQ(rtt_sample, RttStatsPeer::GetQuarterWindowRtt(&rtt_stats_));
144  EXPECT_EQ(rtt_sample, RttStatsPeer::GetHalfWindowRtt(&rtt_stats_));
145  EXPECT_EQ(rtt_sample, rtt_stats_.recent_min_rtt());
146
147  // A new all time low sets both the min_rtt and the recent_min_rtt.
148  rtt_sample = QuicTime::Delta::FromMilliseconds(5);
149  rtt_stats_.UpdateRtt(rtt_sample, QuicTime::Delta::Zero(), now);
150
151  EXPECT_EQ(rtt_sample, rtt_stats_.min_rtt());
152  EXPECT_EQ(rtt_sample, RttStatsPeer::GetQuarterWindowRtt(&rtt_stats_));
153  EXPECT_EQ(rtt_sample, RttStatsPeer::GetHalfWindowRtt(&rtt_stats_));
154  EXPECT_EQ(rtt_sample, rtt_stats_.recent_min_rtt());
155}
156
157TEST_F(RttStatsTest, ExpireSmoothedMetrics) {
158  QuicTime::Delta initial_rtt = QuicTime::Delta::FromMilliseconds(10);
159  rtt_stats_.UpdateRtt(initial_rtt, QuicTime::Delta::Zero(), QuicTime::Zero());
160  EXPECT_EQ(initial_rtt, rtt_stats_.min_rtt());
161  EXPECT_EQ(initial_rtt, rtt_stats_.recent_min_rtt());
162  EXPECT_EQ(initial_rtt, rtt_stats_.SmoothedRtt());
163
164  EXPECT_EQ(initial_rtt.Multiply(0.5), rtt_stats_.mean_deviation());
165
166  // Update once with a 20ms RTT.
167  QuicTime::Delta doubled_rtt = initial_rtt.Multiply(2);
168  rtt_stats_.UpdateRtt(doubled_rtt, QuicTime::Delta::Zero(), QuicTime::Zero());
169  EXPECT_EQ(initial_rtt.Multiply(1.125), rtt_stats_.SmoothedRtt());
170
171  // Expire the smoothed metrics, increasing smoothed rtt and mean deviation.
172  rtt_stats_.ExpireSmoothedMetrics();
173  EXPECT_EQ(doubled_rtt, rtt_stats_.SmoothedRtt());
174  EXPECT_EQ(initial_rtt.Multiply(0.875), rtt_stats_.mean_deviation());
175
176  // Now go back down to 5ms and expire the smoothed metrics, and ensure the
177  // mean deviation increases to 15ms.
178  QuicTime::Delta half_rtt = initial_rtt.Multiply(0.5);
179  rtt_stats_.UpdateRtt(half_rtt, QuicTime::Delta::Zero(), QuicTime::Zero());
180  EXPECT_GT(doubled_rtt, rtt_stats_.SmoothedRtt());
181  EXPECT_LT(initial_rtt, rtt_stats_.mean_deviation());
182}
183
184}  // namespace test
185}  // namespace net
186