1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
|
// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package time
import (
"errors"
"testing"
)
// errNoSamples is returned when testReferenceClocks runs out of samples.
var errNoSamples = errors.New("no samples available")
// testReferenceClocks returns a preset list of samples and cycle counts.
type testReferenceClocks struct {
samples []sample
cycles []TSCValue
}
// Sample implements referenceClocks.Sample, returning the next sample in the list.
func (t *testReferenceClocks) Sample(_ ClockID) (sample, error) {
if len(t.samples) == 0 {
return sample{}, errNoSamples
}
s := t.samples[0]
if len(t.samples) == 1 {
t.samples = nil
} else {
t.samples = t.samples[1:]
}
return s, nil
}
// Cycles implements referenceClocks.Cycles, returning the next TSCValue in the list.
func (t *testReferenceClocks) Cycles() TSCValue {
if len(t.cycles) == 0 {
return 0
}
c := t.cycles[0]
if len(t.cycles) == 1 {
t.cycles = nil
} else {
t.cycles = t.cycles[1:]
}
return c
}
// newTestSampler returns a sampler that collects samples from
// the given sample list and cycle counts from the given cycle list.
func newTestSampler(samples []sample, cycles []TSCValue) *sampler {
return &sampler{
clocks: &testReferenceClocks{
samples: samples,
cycles: cycles,
},
overhead: defaultOverheadCycles,
}
}
// generateSamples generates n samples with the given overhead.
func generateSamples(n int, overhead TSCValue) []sample {
samples := []sample{{before: 1000000, after: 1000000 + overhead, ref: 100}}
for i := 0; i < n-1; i++ {
prev := samples[len(samples)-1]
samples = append(samples, sample{
before: prev.before + 1000000,
after: prev.after + 1000000,
ref: prev.ref + 100,
})
}
return samples
}
// TestSample ensures that samples can be collected.
func TestSample(t *testing.T) {
testCases := []struct {
name string
samples []sample
err error
}{
{
name: "basic",
samples: []sample{
{before: 100000, after: 100000 + defaultOverheadCycles, ref: 100},
},
err: nil,
},
{
// Sample with backwards TSC ignored.
// referenceClock should retry and get errNoSamples.
name: "backwards-tsc-ignored",
samples: []sample{
{before: 100000, after: 90000, ref: 100},
},
err: errNoSamples,
},
{
// Sample far above overhead skipped.
// referenceClock should retry and get errNoSamples.
name: "reject-overhead",
samples: []sample{
{before: 100000, after: 100000 + 5*defaultOverheadCycles, ref: 100},
},
err: errNoSamples,
},
{
// Maximum overhead allowed is bounded.
name: "over-max-overhead",
// Generate a bunch of samples. The reference clock
// needs a while to ramp up its expected overhead.
samples: generateSamples(100, 2*maxOverheadCycles),
err: errOverheadTooHigh,
},
{
// Overhead at maximum overhead is allowed.
name: "max-overhead",
// Generate a bunch of samples. The reference clock
// needs a while to ramp up its expected overhead.
samples: generateSamples(100, maxOverheadCycles),
err: nil,
},
}
for _, tc := range testCases {
t.Run(tc.name, func(t *testing.T) {
s := newTestSampler(tc.samples, nil)
err := s.Sample()
if err != tc.err {
t.Errorf("Sample err got %v want %v", err, tc.err)
}
})
}
}
// TestOutliersIgnored tests that referenceClock ignores samples with very high
// overhead.
func TestOutliersIgnored(t *testing.T) {
s := newTestSampler([]sample{
{before: 100000, after: 100000 + defaultOverheadCycles, ref: 100},
{before: 200000, after: 200000 + defaultOverheadCycles, ref: 200},
{before: 300000, after: 300000 + defaultOverheadCycles, ref: 300},
{before: 400000, after: 400000 + defaultOverheadCycles, ref: 400},
{before: 500000, after: 500000 + 5*defaultOverheadCycles, ref: 500}, // Ignored
{before: 600000, after: 600000 + defaultOverheadCycles, ref: 600},
{before: 700000, after: 700000 + defaultOverheadCycles, ref: 700},
}, nil)
// Collect 5 samples.
for i := 0; i < 5; i++ {
err := s.Sample()
if err != nil {
t.Fatalf("Unexpected error while sampling: %v", err)
}
}
oldest, newest, ok := s.Range()
if !ok {
t.Fatalf("Range not ok")
}
if oldest.ref != 100 {
t.Errorf("oldest.ref got %v want %v", oldest.ref, 100)
}
// We skipped the high-overhead sample.
if newest.ref != 600 {
t.Errorf("newest.ref got %v want %v", newest.ref, 600)
}
}
|
