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perf(chunkenc): intern the custom values for native histograms

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The custom values are the "le" bucket boundaries of native histograms
with custom buckets. They are never modified. It is ok to not copy them
when iterating a chunk, just reference them.

If we will ever have a function that modifies the custom values, like
'trim' for example. That function will have to make a copy on write.

Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>
This commit is contained in:
György Krajcsovits 2025-05-07 14:29:35 +02:00
parent 6dc6785473
commit 6c646657d5
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GPG Key ID: 47A8F9CE80FD7C7F
5 changed files with 30 additions and 41 deletions
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14
model/histogram/float_histogram.go
View File

@ -73,10 +73,8 @@ func (h *FloatHistogram) Copy() *FloatHistogram {
}
if h.UsesCustomBuckets() {
if len(h.CustomValues) != 0 {
c.CustomValues = make([]float64, len(h.CustomValues))
copy(c.CustomValues, h.CustomValues)
}
// Custom values are interned, so no need to copy them.
c.CustomValues = h.CustomValues
} else {
c.ZeroThreshold = h.ZeroThreshold
c.ZeroCount = h.ZeroCount
@ -117,9 +115,8 @@ func (h *FloatHistogram) CopyTo(to *FloatHistogram) {
to.NegativeSpans = clearIfNotNil(to.NegativeSpans)
to.NegativeBuckets = clearIfNotNil(to.NegativeBuckets)
to.CustomValues = resize(to.CustomValues, len(h.CustomValues))
copy(to.CustomValues, h.CustomValues)
// Custom values are interned, so no need to copy them.
to.CustomValues = h.CustomValues
} else {
to.ZeroThreshold = h.ZeroThreshold
to.ZeroCount = h.ZeroCount
@ -130,7 +127,8 @@ func (h *FloatHistogram) CopyTo(to *FloatHistogram) {
to.NegativeBuckets = resize(to.NegativeBuckets, len(h.NegativeBuckets))
copy(to.NegativeBuckets, h.NegativeBuckets)
to.CustomValues = clearIfNotNil(to.CustomValues)
// Custom values are interned, so no need to reset them.
to.CustomValues = nil
}
to.PositiveSpans = resize(to.PositiveSpans, len(h.PositiveSpans))

23
model/histogram/histogram.go
View File

@ -102,10 +102,8 @@ func (h *Histogram) Copy() *Histogram {
}
if h.UsesCustomBuckets() {
if len(h.CustomValues) != 0 {
c.CustomValues = make([]float64, len(h.CustomValues))
copy(c.CustomValues, h.CustomValues)
}
// Custom values are interned, it's ok to copy by reference.
c.CustomValues = h.CustomValues
} else {
c.ZeroThreshold = h.ZeroThreshold
c.ZeroCount = h.ZeroCount
@ -146,9 +144,8 @@ func (h *Histogram) CopyTo(to *Histogram) {
to.NegativeSpans = clearIfNotNil(to.NegativeSpans)
to.NegativeBuckets = clearIfNotNil(to.NegativeBuckets)
to.CustomValues = resize(to.CustomValues, len(h.CustomValues))
copy(to.CustomValues, h.CustomValues)
// Custom values are interned, it's ok to copy by reference.
to.CustomValues = h.CustomValues
} else {
to.ZeroThreshold = h.ZeroThreshold
to.ZeroCount = h.ZeroCount
@ -158,8 +155,8 @@ func (h *Histogram) CopyTo(to *Histogram) {
to.NegativeBuckets = resize(to.NegativeBuckets, len(h.NegativeBuckets))
copy(to.NegativeBuckets, h.NegativeBuckets)
to.CustomValues = clearIfNotNil(to.CustomValues)
// Custom values are interned, no need to reset.
to.CustomValues = nil
}
to.PositiveSpans = resize(to.PositiveSpans, len(h.PositiveSpans))
@ -379,9 +376,8 @@ func (h *Histogram) ToFloat(fh *FloatHistogram) *FloatHistogram {
fh.ZeroCount = 0
fh.NegativeSpans = clearIfNotNil(fh.NegativeSpans)
fh.NegativeBuckets = clearIfNotNil(fh.NegativeBuckets)
fh.CustomValues = resize(fh.CustomValues, len(h.CustomValues))
copy(fh.CustomValues, h.CustomValues)
// Custom values are interned, it's ok to copy by reference.
fh.CustomValues = h.CustomValues
} else {
fh.ZeroThreshold = h.ZeroThreshold
fh.ZeroCount = float64(h.ZeroCount)
@ -395,7 +391,8 @@ func (h *Histogram) ToFloat(fh *FloatHistogram) *FloatHistogram {
currentNegative += float64(b)
fh.NegativeBuckets[i] = currentNegative
}
fh.CustomValues = clearIfNotNil(fh.CustomValues)
// Custom values are interned, no need to reset.
fh.CustomValues = nil
}
fh.PositiveSpans = resize(fh.PositiveSpans, len(h.PositiveSpans))

4
tsdb/chunkenc/float_histogram.go
View File

@ -946,8 +946,8 @@ func (it *floatHistogramIterator) AtFloatHistogram(fh *histogram.FloatHistogram)
fh.NegativeBuckets = resize(fh.NegativeBuckets, len(it.nBuckets))
copy(fh.NegativeBuckets, it.nBuckets)
fh.CustomValues = resize(fh.CustomValues, len(it.customValues))
copy(fh.CustomValues, it.customValues)
// Custom values are interned. The single copy is in this iterator.
fh.CustomValues = it.customValues
return it.t, fh
}

22
tsdb/chunkenc/histogram.go
View File

@ -201,7 +201,8 @@ type HistogramAppender struct {
schema int32
zThreshold float64
pSpans, nSpans []histogram.Span
customValues []float64
// customValues is read only after the first sample is appended.
customValues []float64
// Although we intend to start new chunks on counter resets, we still
// have to handle negative deltas for gauge histograms. Therefore, even
@ -995,8 +996,8 @@ func (it *histogramIterator) AtHistogram(h *histogram.Histogram) (int64, *histog
h.NegativeBuckets = resize(h.NegativeBuckets, len(it.nBuckets))
copy(h.NegativeBuckets, it.nBuckets)
h.CustomValues = resize(h.CustomValues, len(it.customValues))
copy(h.CustomValues, it.customValues)
// Custom values are interned. The single copy is here in the iterator.
h.CustomValues = it.customValues
return it.t, h
}
@ -1049,8 +1050,8 @@ func (it *histogramIterator) AtFloatHistogram(fh *histogram.FloatHistogram) (int
fh.NegativeBuckets[i] = currentNegative
}
fh.CustomValues = resize(fh.CustomValues, len(it.customValues))
copy(fh.CustomValues, it.customValues)
// Custom values are interned. The single copy is here in the iterator.
fh.CustomValues = it.customValues
return it.t, fh
}
@ -1081,7 +1082,6 @@ func (it *histogramIterator) Reset(b []byte) {
it.atHistogramCalled = false
it.pBuckets, it.nBuckets = nil, nil
it.pSpans, it.nSpans = nil, nil
it.customValues = nil
} else {
it.pBuckets = it.pBuckets[:0]
it.nBuckets = it.nBuckets[:0]
@ -1089,7 +1089,6 @@ func (it *histogramIterator) Reset(b []byte) {
if it.atFloatHistogramCalled {
it.atFloatHistogramCalled = false
it.pFloatBuckets, it.nFloatBuckets = nil, nil
it.customValues = nil
} else {
it.pFloatBuckets = it.pFloatBuckets[:0]
it.nFloatBuckets = it.nFloatBuckets[:0]
@ -1102,6 +1101,7 @@ func (it *histogramIterator) Reset(b []byte) {
it.leading = 0
it.trailing = 0
it.err = nil
it.customValues = nil
}
func (it *histogramIterator) Next() ValueType {
@ -1211,13 +1211,7 @@ func (it *histogramIterator) Next() ValueType {
} else {
it.nSpans = nil
}
if len(it.customValues) > 0 {
newCustomValues := make([]float64, len(it.customValues))
copy(newCustomValues, it.customValues)
it.customValues = newCustomValues
} else {
it.customValues = nil
}
// it.CustomValues are interned, so we don't need to copy them.
}
if it.atHistogramCalled {

8
tsdb/chunkenc/histogram_test.go
View File

@ -1631,7 +1631,7 @@ func TestHistogramUniqueSpansAfterNextWithAtFloatHistogram(t *testing.T) {
require.NotSame(t, &rh1.NegativeSpans[0], &rh2.NegativeSpans[0], "NegativeSpans should be unique between histograms")
}
func TestHistogramUniqueCustomValuesAfterNextWithAtHistogram(t *testing.T) {
func TestHistogramCustomValuesInternedAfterNextWithAtHistogram(t *testing.T) {
// Create two histograms with the same schema and custom values.
h1 := &histogram.Histogram{
Schema: -53,
@ -1674,10 +1674,10 @@ func TestHistogramUniqueCustomValuesAfterNextWithAtHistogram(t *testing.T) {
// Check that the spans and custom values for h1 and h2 are unique slices.
require.NotSame(t, &rh1.PositiveSpans[0], &rh2.PositiveSpans[0], "PositiveSpans should be unique between histograms")
require.NotSame(t, &rh1.CustomValues[0], &rh2.CustomValues[0], "CustomValues should be unique between histograms")
require.Same(t, &rh1.CustomValues[0], &rh2.CustomValues[0], "CustomValues should be unique between histograms")
}
func TestHistogramUniqueCustomValuesAfterNextWithAtFloatHistogram(t *testing.T) {
func TestHistogramCustomValuesInternedAfterNextWithAtFloatHistogram(t *testing.T) {
// Create two histograms with the same schema and custom values.
h1 := &histogram.Histogram{
Schema: -53,
@ -1720,7 +1720,7 @@ func TestHistogramUniqueCustomValuesAfterNextWithAtFloatHistogram(t *testing.T)
// Check that the spans and custom values for h1 and h2 are unique slices.
require.NotSame(t, &rh1.PositiveSpans[0], &rh2.PositiveSpans[0], "PositiveSpans should be unique between histograms")
require.NotSame(t, &rh1.CustomValues[0], &rh2.CustomValues[0], "CustomValues should be unique between histograms")
require.Same(t, &rh1.CustomValues[0], &rh2.CustomValues[0], "CustomValues should be unique between histograms")
}
func BenchmarkAppendable(b *testing.B) {