Convert metric.Values to slice of values.

The initial impetus for this was that it made unmarshalling sample
values much faster.

Other relevant benchmark changes in ns/op:

Benchmark                                 old        new   speedup
==================================================================
BenchmarkMarshal                       179170     127996     1.4x
BenchmarkUnmarshal                     404984     132186     3.1x

BenchmarkMemoryGetValueAtTime           57801      50050     1.2x
BenchmarkMemoryGetBoundaryValues        64496      53194     1.2x
BenchmarkMemoryGetRangeValues           66585      54065     1.2x

BenchmarkStreamAdd                       45.0       75.3     0.6x
BenchmarkAppendSample1                   1157       1587     0.7x
BenchmarkAppendSample10                  4090       4284     0.95x
BenchmarkAppendSample100                45660      44066     1.0x
BenchmarkAppendSample1000              579084     582380     1.0x
BenchmarkMemoryAppendRepeatingValues 22796594   22005502     1.0x

Overall, this gives us good speedups in the areas where they matter
most: decoding values from disk and accessing the memory storage (which
is also used for views).

Some of the smaller append examples take minimally longer, but the cost
seems to get amortized over larger appends, so I'm not worried about
these. Also, we're currently not bottlenecked on the write path and have
plenty of other optimizations available in that area if it becomes
necessary.

Memory allocations during appends don't change measurably at all.

Change-Id: I7dc7394edea09506976765551f35b138518db9e8

rules/ast/ast.go

@@ -384,7 +384,7 @@ func EvalVectorRange(node VectorNode, start clientmodel.Timestamp, end clientmod
 	for t := start; t.Before(end); t = t.Add(interval) {
 		vector := node.Eval(t, viewAdapter)
 		for _, sample := range vector {
-			samplePair := &metric.SamplePair{
+			samplePair := metric.SamplePair{
 				Value:     sample.Value,
 				Timestamp: sample.Timestamp,
 			}

rules/ast/view_adapter.go

@@ -82,7 +82,7 @@ func (v *viewAdapter) chooseClosestSample(samples metric.Values, timestamp clien
 				continue
 			}
 			sample := candidate
-			closestBefore = sample
+			closestBefore = &sample
 		}
 
 		// Samples after target time.
@@ -96,7 +96,7 @@ func (v *viewAdapter) chooseClosestSample(samples metric.Values, timestamp clien
 				continue
 			}
 			sample := candidate
-			closestAfter = sample
+			closestAfter = &sample
 		}
 	}
 

rules/helpers_test.go

@@ -28,7 +28,7 @@ var testStartTime = clientmodel.Timestamp(0)
 func getTestValueStream(startVal clientmodel.SampleValue, endVal clientmodel.SampleValue, stepVal clientmodel.SampleValue, startTime clientmodel.Timestamp) (resultValues metric.Values) {
 	currentTime := startTime
 	for currentVal := startVal; currentVal <= endVal; currentVal += stepVal {
-		sample := &metric.SamplePair{
+		sample := metric.SamplePair{
 			Value:     currentVal,
 			Timestamp: currentTime,
 		}

storage/metric/leveldb.go

@@ -350,7 +350,7 @@ func (l *LevelDBMetricPersistence) AppendSamples(samples clientmodel.Samples) (e
 			key.Dump(keyDto)
 
 			for _, sample := range chunk {
-				values = append(values, &SamplePair{
+				values = append(values, SamplePair{
 					Timestamp: sample.Timestamp,
 					Value:     sample.Value,
 				})

storage/metric/memory.go

@@ -27,7 +27,7 @@ import (
 const initialSeriesArenaSize = 4 * 60
 
 type stream interface {
-	add(...*SamplePair)
+	add(Values)
 
 	clone() Values
 	expunge(age clientmodel.Timestamp) Values
@@ -53,7 +53,7 @@ func (s *arrayStream) metric() clientmodel.Metric {
 	return s.m
 }
 
-func (s *arrayStream) add(v ...*SamplePair) {
+func (s *arrayStream) add(v Values) {
 	s.Lock()
 	defer s.Unlock()
 
@@ -202,9 +202,11 @@ func (s *memorySeriesStorage) AppendSample(sample *clientmodel.Sample) error {
 	fingerprint := &clientmodel.Fingerprint{}
 	fingerprint.LoadFromMetric(sample.Metric)
 	series := s.getOrCreateSeries(sample.Metric, fingerprint)
-	series.add(&SamplePair{
+	series.add(Values{
+		SamplePair{
 			Value:     sample.Value,
 			Timestamp: sample.Timestamp,
+		},
 	})
 
 	if s.wmCache != nil {
@@ -325,7 +327,7 @@ func (s *memorySeriesStorage) appendSamplesWithoutIndexing(fingerprint *clientmo
 		s.fingerprintToSeries[*fingerprint] = series
 	}
 
-	series.add(samples...)
+	series.add(samples)
 }
 
 func (s *memorySeriesStorage) GetFingerprintsForLabelSet(l clientmodel.LabelSet) (clientmodel.Fingerprints, error) {

storage/metric/memory_test.go

@@ -27,7 +27,7 @@ func BenchmarkStreamAdd(b *testing.B) {
 	s := newArrayStream(clientmodel.Metric{})
 	samples := make(Values, b.N)
 	for i := 0; i < b.N; i++ {
-		samples = append(samples, &SamplePair{
+		samples = append(samples, SamplePair{
 			Timestamp: clientmodel.TimestampFromTime(time.Date(i, 0, 0, 0, 0, 0, 0, time.UTC)),
 			Value:     clientmodel.SampleValue(i),
 		})
@@ -38,7 +38,7 @@ func BenchmarkStreamAdd(b *testing.B) {
 	var pre runtime.MemStats
 	runtime.ReadMemStats(&pre)
 
-	s.add(samples...)
+	s.add(samples)
 
 	var post runtime.MemStats
 	runtime.ReadMemStats(&post)

storage/metric/operation_test.go

@@ -211,7 +211,7 @@ func TestGetValuesAtTimeOp(t *testing.T) {
 			t.Fatalf("%d. expected length %d, got %d", i, len(scenario.out), len(actual))
 		}
 		for j, out := range scenario.out {
-			if !out.Equal(actual[j]) {
+			if !out.Equal(&actual[j]) {
 				t.Fatalf("%d. expected output %v, got %v", i, scenario.out, actual)
 			}
 		}
@@ -464,7 +464,7 @@ func TestGetValuesAtIntervalOp(t *testing.T) {
 		}
 
 		for j, out := range scenario.out {
-			if !out.Equal(actual[j]) {
+			if !out.Equal(&actual[j]) {
 				t.Fatalf("%d. expected output %v, got %v", i, scenario.out, actual)
 			}
 		}
@@ -639,7 +639,7 @@ func TestGetValuesAlongRangeOp(t *testing.T) {
 			t.Fatalf("%d. expected length %d, got %d: %v", i, len(scenario.out), len(actual), actual)
 		}
 		for j, out := range scenario.out {
-			if !out.Equal(actual[j]) {
+			if !out.Equal(&actual[j]) {
 				t.Fatalf("%d. expected output %v, got %v", i, scenario.out, actual)
 			}
 		}
@@ -796,7 +796,7 @@ func TestGetValueRangeAtIntervalOp(t *testing.T) {
 			t.Fatalf("%d. expected length %d, got %d: %v", i, len(scenario.out), len(actual), actual)
 		}
 		for j, out := range scenario.out {
-			if !out.Equal(actual[j]) {
+			if !out.Equal(&actual[j]) {
 				t.Fatalf("%d. expected output %v, got %v", i, scenario.out, actual)
 			}
 		}

storage/metric/sample.go

@@ -57,9 +57,9 @@ func (s *SamplePair) String() string {
 	return fmt.Sprintf("SamplePair at %s of %s", s.Timestamp, s.Value)
 }
 
-// Values is a sortable slice of SamplePair pointers (as in: it implements
+// Values is a sortable slice of SamplePairs (as in: it implements
 // sort.Interface). Sorting happens by Timestamp.
-type Values []*SamplePair
+type Values []SamplePair
 
 // Len implements sort.Interface.
 func (v Values) Len() int {
@@ -84,7 +84,7 @@ func (v Values) Equal(o Values) bool {
 	}
 
 	for i, expected := range v {
-		if !expected.Equal(o[i]) {
+		if !expected.Equal(&o[i]) {
 			return false
 		}
 	}
@@ -182,10 +182,8 @@ func unmarshalValues(buf []byte) Values {
 	}
 	for i := 0; i < n; i++ {
 		offset := formatVersionSize + i*sampleSize
-		v[i] = &SamplePair{
+		v[i].Timestamp = clientmodel.TimestampFromUnix(int64(binary.LittleEndian.Uint64(buf[offset:])))
-			Timestamp: clientmodel.TimestampFromUnix(int64(binary.LittleEndian.Uint64(buf[offset:]))),
+		v[i].Value = clientmodel.SampleValue(math.Float64frombits(binary.LittleEndian.Uint64(buf[offset+8:])))
-			Value:     clientmodel.SampleValue(math.Float64frombits(binary.LittleEndian.Uint64(buf[offset+8:]))),
-		}
 	}
 	return v
 }

storage/metric/sample_test.go

@@ -17,7 +17,7 @@ func TestValuesMarshalAndUnmarshal(t *testing.T) {
 
 	for i, expected := range values {
 		actual := unmarshalled[i]
-		if !actual.Equal(expected) {
+		if !actual.Equal(&expected) {
 			t.Fatalf("%d. got: %v, expected: %v", i, actual, expected)
 		}
 	}
@@ -26,7 +26,7 @@ func TestValuesMarshalAndUnmarshal(t *testing.T) {
 func randomValues(numSamples int) Values {
 	v := make(Values, 0, numSamples)
 	for i := 0; i < numSamples; i++ {
-		v = append(v, &SamplePair{
+		v = append(v, SamplePair{
 			Timestamp: clientmodel.Timestamp(rand.Int63()),
 			Value:     clientmodel.SampleValue(rand.NormFloat64()),
 		})

storage/metric/tiered_test.go

@@ -719,7 +719,7 @@ func testTruncateBefore(t test.Tester) {
 		}
 
 		for j, actualValue := range actual {
-			if !actualValue.Equal(scenario.out[j]) {
+			if !actualValue.Equal(&scenario.out[j]) {
 				t.Fatalf("%d.%d. expected %s, got %s", i, j, scenario.out[j], actualValue)
 			}
 		}