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// Copyright 2018 Google Inc.
//
// 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 (
"testing"
"time"
)
// newTestCalibratedClock returns a CalibratedClock that collects samples from
// the given sample list and cycle counts from the given cycle list.
func newTestCalibratedClock(samples []sample, cycles []TSCValue) *CalibratedClock {
return &CalibratedClock{
ref: newTestSampler(samples, cycles),
}
}
func TestConstantFrequency(t *testing.T) {
// Perfectly constant frequency.
samples := []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 + defaultOverheadCycles, ref: 500},
{before: 600000, after: 600000 + defaultOverheadCycles, ref: 600},
{before: 700000, after: 700000 + defaultOverheadCycles, ref: 700},
}
c := newTestCalibratedClock(samples, nil)
// Update from all samples.
for range samples {
c.Update()
}
c.mu.RLock()
if !c.ready {
c.mu.RUnlock()
t.Fatalf("clock not ready")
}
// A bit after the last sample.
now, ok := c.params.ComputeTime(750000)
c.mu.RUnlock()
if !ok {
t.Fatalf("ComputeTime ok got %v want true", ok)
}
t.Logf("now: %v", now)
// Time should be between the current sample and where we'd expect the
// next sample.
if now < 700 || now > 800 {
t.Errorf("now got %v want > 700 && < 800", now)
}
}
func TestErrorCorrection(t *testing.T) {
testCases := []struct {
name string
samples [5]sample
projectedTimeStart int64
projectedTimeEnd int64
}{
// Initial calibration should be ~1MHz for each of these, and
// the reference clock changes in samples[2].
{
name: "slow-down",
samples: [5]sample{
{before: 1000000, after: 1000001, ref: ReferenceNS(1 * ApproxUpdateInterval.Nanoseconds())},
{before: 2000000, after: 2000001, ref: ReferenceNS(2 * ApproxUpdateInterval.Nanoseconds())},
// Reference clock has slowed down, causing 100ms of error.
{before: 3010000, after: 3010001, ref: ReferenceNS(3 * ApproxUpdateInterval.Nanoseconds())},
{before: 4020000, after: 4020001, ref: ReferenceNS(4 * ApproxUpdateInterval.Nanoseconds())},
{before: 5030000, after: 5030001, ref: ReferenceNS(5 * ApproxUpdateInterval.Nanoseconds())},
},
projectedTimeStart: 3005 * time.Millisecond.Nanoseconds(),
projectedTimeEnd: 3015 * time.Millisecond.Nanoseconds(),
},
{
name: "speed-up",
samples: [5]sample{
{before: 1000000, after: 1000001, ref: ReferenceNS(1 * ApproxUpdateInterval.Nanoseconds())},
{before: 2000000, after: 2000001, ref: ReferenceNS(2 * ApproxUpdateInterval.Nanoseconds())},
// Reference clock has sped up, causing 100ms of error.
{before: 2990000, after: 2990001, ref: ReferenceNS(3 * ApproxUpdateInterval.Nanoseconds())},
{before: 3980000, after: 3980001, ref: ReferenceNS(4 * ApproxUpdateInterval.Nanoseconds())},
{before: 4970000, after: 4970001, ref: ReferenceNS(5 * ApproxUpdateInterval.Nanoseconds())},
},
projectedTimeStart: 2985 * time.Millisecond.Nanoseconds(),
projectedTimeEnd: 2995 * time.Millisecond.Nanoseconds(),
},
}
for _, tc := range testCases {
t.Run(tc.name, func(t *testing.T) {
c := newTestCalibratedClock(tc.samples[:], nil)
// Initial calibration takes two updates.
_, ok := c.Update()
if ok {
t.Fatalf("Update ready too early")
}
params, ok := c.Update()
if !ok {
t.Fatalf("Update not ready")
}
// Initial calibration is ~1MHz.
hz := params.Frequency
if hz < 990000 || hz > 1010000 {
t.Fatalf("Frequency got %v want > 990kHz && < 1010kHz", hz)
}
// Project time at the next update. Given the 1MHz
// calibration, it is expected to be ~3.1s/2.9s, not
// the actual 3s.
//
// N.B. the next update time is the "after" time above.
projected, ok := params.ComputeTime(tc.samples[2].after)
if !ok {
t.Fatalf("ComputeTime ok got %v want true", ok)
}
if projected < tc.projectedTimeStart || projected > tc.projectedTimeEnd {
t.Fatalf("ComputeTime(%v) got %v want > %v && < %v", tc.samples[2].after, projected, tc.projectedTimeStart, tc.projectedTimeEnd)
}
// Update again to see the changed reference clock.
params, ok = c.Update()
if !ok {
t.Fatalf("Update not ready")
}
// We now know that TSC = tc.samples[2].after -> 3s,
// but with the previous params indicated that TSC
// tc.samples[2].after -> 3.5s/2.5s. We can't allow the
// clock to go backwards, and having the clock jump
// forwards is undesirable. There should be a smooth
// transition that corrects the clock error over time.
// Check that the clock is continuous at TSC =
// tc.samples[2].after.
newProjected, ok := params.ComputeTime(tc.samples[2].after)
if !ok {
t.Fatalf("ComputeTime ok got %v want true", ok)
}
if newProjected != projected {
t.Errorf("Discontinuous time; ComputeTime(%v) got %v want %v", tc.samples[2].after, newProjected, projected)
}
// As the reference clock stablizes, ensure that the clock error
// decreases.
initialErr := c.errorNS
t.Logf("initial error: %v ns", initialErr)
_, ok = c.Update()
if !ok {
t.Fatalf("Update not ready")
}
if c.errorNS.Magnitude() > initialErr.Magnitude() {
t.Errorf("errorNS increased, got %v want |%v| <= |%v|", c.errorNS, c.errorNS, initialErr)
}
_, ok = c.Update()
if !ok {
t.Fatalf("Update not ready")
}
if c.errorNS.Magnitude() > initialErr.Magnitude() {
t.Errorf("errorNS increased, got %v want |%v| <= |%v|", c.errorNS, c.errorNS, initialErr)
}
t.Logf("final error: %v ns", c.errorNS)
})
}
}
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