diff --git a/metrics/runtimehistogram.go b/metrics/runtimehistogram.go index 698cf97c18..6b0c6a4c40 100644 --- a/metrics/runtimehistogram.go +++ b/metrics/runtimehistogram.go @@ -17,13 +17,13 @@ func getOrRegisterRuntimeHistogram(name string, scale float64, r Registry) *runt // runtimeHistogram wraps a runtime/metrics histogram. type runtimeHistogram struct { - v atomic.Value + v atomic.Value // v is a pointer to a metrics.Float64Histogram scaleFactor float64 } func newRuntimeHistogram(scale float64) *runtimeHistogram { h := &runtimeHistogram{scaleFactor: scale} - h.update(&metrics.Float64Histogram{}) + h.update(new(metrics.Float64Histogram)) return h } @@ -41,22 +41,17 @@ func (h *runtimeHistogram) update(mh *metrics.Float64Histogram) { return } - s := runtimeHistogramSnapshot{ + s := metrics.Float64Histogram{ Counts: make([]uint64, len(mh.Counts)), Buckets: make([]float64, len(mh.Buckets)), } copy(s.Counts, mh.Counts) - copy(s.Buckets, mh.Buckets) - for i, b := range s.Buckets { + for i, b := range mh.Buckets { s.Buckets[i] = b * h.scaleFactor } h.v.Store(&s) } -func (h *runtimeHistogram) load() *runtimeHistogramSnapshot { - return h.v.Load().(*runtimeHistogramSnapshot) -} - func (h *runtimeHistogram) Clear() { panic("runtimeHistogram does not support Clear") } @@ -64,54 +59,94 @@ func (h *runtimeHistogram) Update(int64) { panic("runtimeHistogram does not support Update") } -// Snapshot returns a non-changing cop of the histogram. +// Snapshot returns a non-changing copy of the histogram. func (h *runtimeHistogram) Snapshot() HistogramSnapshot { - return h.load() + hist := h.v.Load().(*metrics.Float64Histogram) + return newRuntimeHistogramSnapshot(hist) } -type runtimeHistogramSnapshot metrics.Float64Histogram +type runtimeHistogramSnapshot struct { + internal *metrics.Float64Histogram + calculated bool + // The following fields are (lazily) calculated based on 'internal' + mean float64 + count int64 + min int64 // min is the lowest sample value. + max int64 // max is the highest sample value. + variance float64 +} -func (h *runtimeHistogramSnapshot) Snapshot() HistogramSnapshot { - return h +func newRuntimeHistogramSnapshot(h *metrics.Float64Histogram) *runtimeHistogramSnapshot { + return &runtimeHistogramSnapshot{ + internal: h, + } +} + +// calc calculates the values for the snapshot. This method is not threadsafe. +func (h *runtimeHistogramSnapshot) calc() { + h.calculated = true + var ( + count int64 // number of samples + sum float64 // approx sum of all sample values + minSet = false + min int64 + max float64 + ) + if len(h.internal.Counts) == 0 { + return + } + for i, c := range h.internal.Counts { + count += int64(c) + midpoint := h.midpoint(i) + sum += midpoint * float64(c) + if c == 0 { + continue + } + + if c > 0 && !minSet { + minSet = true + min = int64(math.Floor(h.internal.Buckets[i])) + } + if count > 0 { + edge := h.internal.Buckets[i+1] + if math.IsInf(edge, 1) { + edge = h.internal.Buckets[i] + } + if edge > max { + max = edge + } + } + } + h.min = min + h.max = int64(max) + h.mean = sum / float64(count) + h.count = count } // Count returns the sample count. func (h *runtimeHistogramSnapshot) Count() int64 { - var count int64 - for _, c := range h.Counts { - count += int64(c) + if !h.calculated { + h.calc() } - return count + return h.count } // Size returns the size of the sample at the time the snapshot was taken. func (h *runtimeHistogramSnapshot) Size() int { - return len(h.Counts) + return len(h.internal.Counts) } // Mean returns an approximation of the mean. func (h *runtimeHistogramSnapshot) Mean() float64 { - if len(h.Counts) == 0 { - return 0 + if !h.calculated { + h.calc() } - mean, _ := h.mean() - return mean -} - -// mean computes the mean and also the total sample count. -func (h *runtimeHistogramSnapshot) mean() (mean, totalCount float64) { - var sum float64 - for i, c := range h.Counts { - midpoint := h.midpoint(i) - sum += midpoint * float64(c) - totalCount += float64(c) - } - return sum / totalCount, totalCount + return h.mean } func (h *runtimeHistogramSnapshot) midpoint(bucket int) float64 { - high := h.Buckets[bucket+1] - low := h.Buckets[bucket] + high := h.internal.Buckets[bucket+1] + low := h.internal.Buckets[bucket] if math.IsInf(high, 1) { // The edge of the highest bucket can be +Inf, and it's supposed to mean that this // bucket contains all remaining samples > low. We can't get the middle of an @@ -133,23 +168,31 @@ func (h *runtimeHistogramSnapshot) StdDev() float64 { // Variance approximates the variance of the histogram. func (h *runtimeHistogramSnapshot) Variance() float64 { - if len(h.Counts) == 0 { + if len(h.internal.Counts) == 0 { return 0 } - - mean, totalCount := h.mean() - if totalCount <= 1 { + if !h.calculated { + h.calc() + } + if h.count <= 1 { // There is no variance when there are zero or one items. return 0 } - + // Variance is not calculated in 'calc', because it requires a second iteration. + // Therefore we calculate it lazily in this method, triggered either by + // a direct call to Variance or via StdDev. + if h.variance != 0.0 { + return h.variance + } var sum float64 - for i, c := range h.Counts { + + for i, c := range h.internal.Counts { midpoint := h.midpoint(i) - d := midpoint - mean + d := midpoint - h.mean sum += float64(c) * (d * d) } - return sum / (totalCount - 1) + h.variance = sum / float64(h.count-1) + return h.variance } // Percentile computes the p'th percentile value. @@ -184,11 +227,11 @@ func (h *runtimeHistogramSnapshot) Percentiles(ps []float64) []float64 { func (h *runtimeHistogramSnapshot) computePercentiles(thresh []float64) { var totalCount float64 - for i, count := range h.Counts { + for i, count := range h.internal.Counts { totalCount += float64(count) for len(thresh) > 0 && thresh[0] < totalCount { - thresh[0] = h.Buckets[i] + thresh[0] = h.internal.Buckets[i] thresh = thresh[1:] } if len(thresh) == 0 { @@ -203,34 +246,25 @@ func (h *runtimeHistogramSnapshot) computePercentiles(thresh []float64) { // Max returns the highest sample value. func (h *runtimeHistogramSnapshot) Max() int64 { - for i := len(h.Counts) - 1; i >= 0; i-- { - count := h.Counts[i] - if count > 0 { - edge := h.Buckets[i+1] - if math.IsInf(edge, 1) { - edge = h.Buckets[i] - } - return int64(math.Ceil(edge)) - } + if !h.calculated { + h.calc() } - return 0 + return h.max } // Min returns the lowest sample value. func (h *runtimeHistogramSnapshot) Min() int64 { - for i, count := range h.Counts { - if count > 0 { - return int64(math.Floor(h.Buckets[i])) - } + if !h.calculated { + h.calc() } - return 0 + return h.min } // Sum returns the sum of all sample values. func (h *runtimeHistogramSnapshot) Sum() int64 { var sum float64 - for i := range h.Counts { - sum += h.Buckets[i] * float64(h.Counts[i]) + for i := range h.internal.Counts { + sum += h.internal.Buckets[i] * float64(h.internal.Counts[i]) } return int64(math.Ceil(sum)) } diff --git a/metrics/runtimehistogram_test.go b/metrics/runtimehistogram_test.go index d53a014383..cf7e36420a 100644 --- a/metrics/runtimehistogram_test.go +++ b/metrics/runtimehistogram_test.go @@ -1,11 +1,14 @@ package metrics import ( + "bytes" + "encoding/gob" "fmt" "math" "reflect" "runtime/metrics" "testing" + "time" ) var _ Histogram = (*runtimeHistogram)(nil) @@ -74,7 +77,7 @@ func TestRuntimeHistogramStats(t *testing.T) { for i, test := range tests { t.Run(fmt.Sprint(i), func(t *testing.T) { - s := runtimeHistogramSnapshot(test.h) + s := RuntimeHistogramFromData(1.0, &test.h).Snapshot() if v := s.Count(); v != test.Count { t.Errorf("Count() = %v, want %v", v, test.Count) @@ -121,13 +124,39 @@ func approxEqual(x, y, ε float64) bool { // This test verifies that requesting Percentiles in unsorted order // returns them in the requested order. func TestRuntimeHistogramStatsPercentileOrder(t *testing.T) { - p := runtimeHistogramSnapshot{ + s := RuntimeHistogramFromData(1.0, &metrics.Float64Histogram{ Counts: []uint64{1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, Buckets: []float64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, - } - result := p.Percentiles([]float64{1, 0.2, 0.5, 0.1, 0.2}) + }).Snapshot() + result := s.Percentiles([]float64{1, 0.2, 0.5, 0.1, 0.2}) expected := []float64{10, 2, 5, 1, 2} if !reflect.DeepEqual(result, expected) { t.Fatal("wrong result:", result) } } + +func BenchmarkRuntimeHistogramSnapshotRead(b *testing.B) { + var sLatency = "7\xff\x81\x03\x01\x01\x10Float64Histogram\x01\xff\x82\x00\x01\x02\x01\x06Counts\x01\xff\x84\x00\x01\aBuckets\x01\xff\x86\x00\x00\x00\x16\xff\x83\x02\x01\x01\b[]uint64\x01\xff\x84\x00\x01\x06\x00\x00\x17\xff\x85\x02\x01\x01\t[]float64\x01\xff\x86\x00\x01\b\x00\x00\xfe\x06T\xff\x82\x01\xff\xa2\x00\xfe\r\xef\x00\x01\x02\x02\x04\x05\x04\b\x15\x17 B?6.L;$!2) \x1a? 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