Refactoring of sparse histograms
Signed-off-by: beorn7 <beorn@grafana.com>
This commit is contained in:
beorn7
parent
24099603bc
commit
263be8dab7
|
|
@ -563,13 +563,7 @@ func (hc *histogramCounts) observe(v float64, bucket int, doSparse bool) {
|
|||
if bucket < len(hc.buckets) {
|
||||
atomic.AddUint64(&hc.buckets[bucket], 1)
|
||||
}
|
||||
for {
|
||||
oldBits := atomic.LoadUint64(&hc.sumBits)
|
||||
newBits := math.Float64bits(math.Float64frombits(oldBits) + v)
|
||||
if atomic.CompareAndSwapUint64(&hc.sumBits, oldBits, newBits) {
|
||||
break
|
||||
}
|
||||
}
|
||||
atomicAddFloat(&hc.sumBits, v)
|
||||
if doSparse {
|
||||
var (
|
||||
sparseKey int
|
||||
|
|
@ -685,10 +679,7 @@ func (h *histogram) Write(out *dto.Metric) error {
|
|||
hotCounts := h.counts[n>>63]
|
||||
coldCounts := h.counts[(^n)>>63]
|
||||
|
||||
// Await cooldown.
|
||||
for count != atomic.LoadUint64(&coldCounts.count) {
|
||||
runtime.Gosched() // Let observations get work done.
|
||||
}
|
||||
waitForCooldown(count, coldCounts)
|
||||
|
||||
his := &dto.Histogram{
|
||||
Bucket: make([]*dto.Bucket, len(h.upperBounds)),
|
||||
|
|
@ -718,29 +709,12 @@ func (h *histogram) Write(out *dto.Metric) error {
|
|||
}
|
||||
his.Bucket = append(his.Bucket, b)
|
||||
}
|
||||
// Add all the cold counts to the new hot counts and reset the cold counts.
|
||||
atomic.AddUint64(&hotCounts.count, count)
|
||||
atomic.StoreUint64(&coldCounts.count, 0)
|
||||
for {
|
||||
oldBits := atomic.LoadUint64(&hotCounts.sumBits)
|
||||
newBits := math.Float64bits(math.Float64frombits(oldBits) + his.GetSampleSum())
|
||||
if atomic.CompareAndSwapUint64(&hotCounts.sumBits, oldBits, newBits) {
|
||||
atomic.StoreUint64(&coldCounts.sumBits, 0)
|
||||
break
|
||||
}
|
||||
}
|
||||
for i := range h.upperBounds {
|
||||
atomic.AddUint64(&hotCounts.buckets[i], atomic.LoadUint64(&coldCounts.buckets[i]))
|
||||
atomic.StoreUint64(&coldCounts.buckets[i], 0)
|
||||
}
|
||||
if h.sparseSchema > math.MinInt32 {
|
||||
his.SbZeroThreshold = proto.Float64(math.Float64frombits(atomic.LoadUint64(&coldCounts.sparseZeroThresholdBits)))
|
||||
his.SbSchema = proto.Int32(atomic.LoadInt32(&coldCounts.sparseSchema))
|
||||
zeroBucket := atomic.LoadUint64(&coldCounts.sparseZeroBucket)
|
||||
|
||||
defer func() {
|
||||
atomic.AddUint64(&hotCounts.sparseZeroBucket, zeroBucket)
|
||||
atomic.StoreUint64(&coldCounts.sparseZeroBucket, 0)
|
||||
coldCounts.sparseBucketsPositive.Range(addAndReset(&hotCounts.sparseBucketsPositive, &hotCounts.sparseBucketsNumber))
|
||||
coldCounts.sparseBucketsNegative.Range(addAndReset(&hotCounts.sparseBucketsNegative, &hotCounts.sparseBucketsNumber))
|
||||
}()
|
||||
|
|
@ -749,6 +723,7 @@ func (h *histogram) Write(out *dto.Metric) error {
|
|||
his.SbNegative = makeSparseBuckets(&coldCounts.sparseBucketsNegative)
|
||||
his.SbPositive = makeSparseBuckets(&coldCounts.sparseBucketsPositive)
|
||||
}
|
||||
addAndResetCounts(hotCounts, coldCounts)
|
||||
return nil
|
||||
}
|
||||
|
||||
|
|
@ -809,102 +784,98 @@ func (h *histogram) limitSparseBuckets(counts *histogramCounts, value float64, b
|
|||
if h.sparseMaxBuckets >= atomic.LoadUint32(&hotCounts.sparseBucketsNumber) {
|
||||
return // Bucket limit not exceeded after all.
|
||||
}
|
||||
// Try the various strategies in order.
|
||||
if h.maybeReset(hotCounts, coldCounts, coldIdx, value, bucket) {
|
||||
return
|
||||
}
|
||||
if h.maybeWidenZeroBucket(hotCounts, coldCounts) {
|
||||
return
|
||||
}
|
||||
h.doubleBucketWidth(hotCounts, coldCounts)
|
||||
}
|
||||
|
||||
// (1) Ideally, we can reset the whole histogram.
|
||||
|
||||
// maybyReset resests the whole histogram if at least h.sparseMinResetDuration
|
||||
// has been passed. It returns true if the histogram has been reset. The caller
|
||||
// must have locked h.mtx.
|
||||
func (h *histogram) maybeReset(hot, cold *histogramCounts, coldIdx uint64, value float64, bucket int) bool {
|
||||
// We are using the possibly mocked h.now() rather than
|
||||
// time.Since(h.lastResetTime) to enable testing.
|
||||
if h.sparseMinResetDuration > 0 && h.now().Sub(h.lastResetTime) >= h.sparseMinResetDuration {
|
||||
if h.sparseMinResetDuration == 0 || h.now().Sub(h.lastResetTime) < h.sparseMinResetDuration {
|
||||
return false
|
||||
}
|
||||
// Completely reset coldCounts.
|
||||
h.resetCounts(coldCounts)
|
||||
h.resetCounts(cold)
|
||||
// Repeat the latest observation to not lose it completely.
|
||||
coldCounts.observe(value, bucket, true)
|
||||
cold.observe(value, bucket, true)
|
||||
// Make coldCounts the new hot counts while ressetting countAndHotIdx.
|
||||
n := atomic.SwapUint64(&h.countAndHotIdx, (coldIdx<<63)+1)
|
||||
count := n & ((1 << 63) - 1)
|
||||
// Wait for the formerly hot counts to cool down.
|
||||
for count != atomic.LoadUint64(&hotCounts.count) {
|
||||
runtime.Gosched() // Let observations get work done.
|
||||
}
|
||||
waitForCooldown(count, hot)
|
||||
// Finally, reset the formerly hot counts, too.
|
||||
h.resetCounts(hotCounts)
|
||||
h.resetCounts(hot)
|
||||
h.lastResetTime = h.now()
|
||||
return
|
||||
}
|
||||
return true
|
||||
}
|
||||
|
||||
// (2) Try widening the zero bucket.
|
||||
currentZeroThreshold := math.Float64frombits(atomic.LoadUint64(&hotCounts.sparseZeroThresholdBits))
|
||||
switch { // Use switch rather than if to be able to break out of it.
|
||||
case h.sparseMaxZeroThreshold > currentZeroThreshold:
|
||||
// maybeWidenZeroBucket widens the zero bucket until it includes the existing
|
||||
// buckets closest to the zero bucket (which could be two, if an equidistant
|
||||
// negative and a positive bucket exists, but usually it's only one bucket to be
|
||||
// merged into the new wider zero bucket). h.sparseMaxZeroThreshold limits how
|
||||
// far the zero bucket can be extended, and if that's not enough to include an
|
||||
// existing bucket, the method returns false. The caller must have locked h.mtx.
|
||||
func (h *histogram) maybeWidenZeroBucket(hot, cold *histogramCounts) bool {
|
||||
currentZeroThreshold := math.Float64frombits(atomic.LoadUint64(&hot.sparseZeroThresholdBits))
|
||||
if currentZeroThreshold >= h.sparseMaxZeroThreshold {
|
||||
return false
|
||||
}
|
||||
// Find the key of the bucket closest to zero.
|
||||
smallestKey := findSmallestKey(&hotCounts.sparseBucketsPositive)
|
||||
smallestNegativeKey := findSmallestKey(&hotCounts.sparseBucketsNegative)
|
||||
smallestKey := findSmallestKey(&hot.sparseBucketsPositive)
|
||||
smallestNegativeKey := findSmallestKey(&hot.sparseBucketsNegative)
|
||||
if smallestNegativeKey < smallestKey {
|
||||
smallestKey = smallestNegativeKey
|
||||
}
|
||||
if smallestKey == math.MaxInt32 {
|
||||
break
|
||||
return false
|
||||
}
|
||||
newZeroThreshold := getLe(smallestKey, atomic.LoadInt32(&hotCounts.sparseSchema))
|
||||
newZeroThreshold := getLe(smallestKey, atomic.LoadInt32(&hot.sparseSchema))
|
||||
if newZeroThreshold > h.sparseMaxZeroThreshold {
|
||||
break // New threshold would exceed the max threshold.
|
||||
return false // New threshold would exceed the max threshold.
|
||||
}
|
||||
atomic.StoreUint64(&coldCounts.sparseZeroThresholdBits, math.Float64bits(newZeroThreshold))
|
||||
atomic.StoreUint64(&cold.sparseZeroThresholdBits, math.Float64bits(newZeroThreshold))
|
||||
// Remove applicable buckets.
|
||||
if _, loaded := coldCounts.sparseBucketsNegative.LoadAndDelete(smallestKey); loaded {
|
||||
atomic.AddUint32(&coldCounts.sparseBucketsNumber, ^uint32(0)) // Decrement, see https://pkg.go.dev/sync/atomic#AddUint32
|
||||
if _, loaded := cold.sparseBucketsNegative.LoadAndDelete(smallestKey); loaded {
|
||||
atomicDecUint32(&cold.sparseBucketsNumber)
|
||||
}
|
||||
if _, loaded := coldCounts.sparseBucketsPositive.LoadAndDelete(smallestKey); loaded {
|
||||
atomic.AddUint32(&coldCounts.sparseBucketsNumber, ^uint32(0)) // Decrement, see https://pkg.go.dev/sync/atomic#AddUint32
|
||||
if _, loaded := cold.sparseBucketsPositive.LoadAndDelete(smallestKey); loaded {
|
||||
atomicDecUint32(&cold.sparseBucketsNumber)
|
||||
}
|
||||
// Make coldCounts the new hot counts.
|
||||
// Make cold counts the new hot counts.
|
||||
n := atomic.AddUint64(&h.countAndHotIdx, 1<<63)
|
||||
count := n & ((1 << 63) - 1)
|
||||
// Swap the pointer names to represent the new roles and make
|
||||
// the rest less confusing.
|
||||
hotCounts, coldCounts = coldCounts, hotCounts
|
||||
// Wait for the (new) cold counts to cool down.
|
||||
for count != atomic.LoadUint64(&coldCounts.count) {
|
||||
runtime.Gosched() // Let observations get work done.
|
||||
}
|
||||
// Add all the cold counts to the new hot counts, while merging
|
||||
// the newly deleted buckets into the wider zero bucket, and
|
||||
// reset and adjust the cold counts.
|
||||
// TODO(beorn7): Maybe make it more DRY, cf. Write() method. Maybe
|
||||
// it's too different, though...
|
||||
atomic.AddUint64(&hotCounts.count, count)
|
||||
atomic.StoreUint64(&coldCounts.count, 0)
|
||||
for {
|
||||
hotBits := atomic.LoadUint64(&hotCounts.sumBits)
|
||||
coldBits := atomic.LoadUint64(&coldCounts.sumBits)
|
||||
newBits := math.Float64bits(math.Float64frombits(hotBits) + math.Float64frombits(coldBits))
|
||||
if atomic.CompareAndSwapUint64(&hotCounts.sumBits, hotBits, newBits) {
|
||||
atomic.StoreUint64(&coldCounts.sumBits, 0)
|
||||
break
|
||||
}
|
||||
}
|
||||
for i := range h.upperBounds {
|
||||
atomic.AddUint64(&hotCounts.buckets[i], atomic.LoadUint64(&coldCounts.buckets[i]))
|
||||
atomic.StoreUint64(&coldCounts.buckets[i], 0)
|
||||
}
|
||||
atomic.AddUint64(&hotCounts.sparseZeroBucket, atomic.LoadUint64(&coldCounts.sparseZeroBucket))
|
||||
atomic.StoreUint64(&coldCounts.sparseZeroBucket, 0)
|
||||
atomic.StoreUint64(&coldCounts.sparseZeroThresholdBits, math.Float64bits(newZeroThreshold))
|
||||
|
||||
hot, cold = cold, hot
|
||||
waitForCooldown(count, cold)
|
||||
// Add all the now cold counts to the new hot counts...
|
||||
addAndResetCounts(hot, cold)
|
||||
// ...adjust the new zero threshold in the cold counts, too...
|
||||
atomic.StoreUint64(&cold.sparseZeroThresholdBits, math.Float64bits(newZeroThreshold))
|
||||
// ...and then merge the newly deleted buckets into the wider zero
|
||||
// bucket.
|
||||
mergeAndDeleteOrAddAndReset := func(hotBuckets, coldBuckets *sync.Map) func(k, v interface{}) bool {
|
||||
return func(k, v interface{}) bool {
|
||||
key := k.(int)
|
||||
bucket := v.(*int64)
|
||||
if key == smallestKey {
|
||||
// Merge into hot zero bucket...
|
||||
atomic.AddUint64(&hotCounts.sparseZeroBucket, uint64(atomic.LoadInt64(bucket)))
|
||||
atomic.AddUint64(&hot.sparseZeroBucket, uint64(atomic.LoadInt64(bucket)))
|
||||
// ...and delete from cold counts.
|
||||
coldBuckets.Delete(key)
|
||||
atomic.AddUint32(&coldCounts.sparseBucketsNumber, ^uint32(0)) // Decrement, see https://pkg.go.dev/sync/atomic#AddUint32
|
||||
atomicDecUint32(&cold.sparseBucketsNumber)
|
||||
} else {
|
||||
// Add to corresponding hot bucket...
|
||||
if addToSparseBucket(hotBuckets, key, atomic.LoadInt64(bucket)) {
|
||||
atomic.AddUint32(&hotCounts.sparseBucketsNumber, 1)
|
||||
atomic.AddUint32(&hot.sparseBucketsNumber, 1)
|
||||
}
|
||||
// ...and reset cold bucket.
|
||||
atomic.StoreInt64(bucket, 0)
|
||||
|
|
@ -913,55 +884,38 @@ func (h *histogram) limitSparseBuckets(counts *histogramCounts, value float64, b
|
|||
}
|
||||
}
|
||||
|
||||
coldCounts.sparseBucketsPositive.Range(mergeAndDeleteOrAddAndReset(&hotCounts.sparseBucketsPositive, &coldCounts.sparseBucketsPositive))
|
||||
coldCounts.sparseBucketsNegative.Range(mergeAndDeleteOrAddAndReset(&hotCounts.sparseBucketsNegative, &coldCounts.sparseBucketsNegative))
|
||||
return
|
||||
}
|
||||
cold.sparseBucketsPositive.Range(mergeAndDeleteOrAddAndReset(&hot.sparseBucketsPositive, &cold.sparseBucketsPositive))
|
||||
cold.sparseBucketsNegative.Range(mergeAndDeleteOrAddAndReset(&hot.sparseBucketsNegative, &cold.sparseBucketsNegative))
|
||||
return true
|
||||
}
|
||||
|
||||
// (3) Ultima ratio: Doubling of the bucket width AKA halving the resolution AKA decrementing sparseSchema.
|
||||
coldSchema := atomic.LoadInt32(&coldCounts.sparseSchema)
|
||||
// doubleBucketWidth doubles the bucket width (by decrementing the schema
|
||||
// number). Note that very sparse buckets could lead to a low reduction of the
|
||||
// bucket count (or even no reduction at all). The method does nothing if the
|
||||
// schema is already -4.
|
||||
func (h *histogram) doubleBucketWidth(hot, cold *histogramCounts) {
|
||||
coldSchema := atomic.LoadInt32(&cold.sparseSchema)
|
||||
if coldSchema == -4 {
|
||||
return // Already at lowest resolution.
|
||||
}
|
||||
coldSchema--
|
||||
atomic.StoreInt32(&coldCounts.sparseSchema, coldSchema)
|
||||
atomic.StoreInt32(&cold.sparseSchema, coldSchema)
|
||||
// Play it simple and just delete all cold buckets.
|
||||
atomic.StoreUint32(&coldCounts.sparseBucketsNumber, 0)
|
||||
deleteSyncMap(&coldCounts.sparseBucketsNegative)
|
||||
deleteSyncMap(&coldCounts.sparseBucketsPositive)
|
||||
atomic.StoreUint32(&cold.sparseBucketsNumber, 0)
|
||||
deleteSyncMap(&cold.sparseBucketsNegative)
|
||||
deleteSyncMap(&cold.sparseBucketsPositive)
|
||||
// Make coldCounts the new hot counts.
|
||||
n = atomic.AddUint64(&h.countAndHotIdx, 1<<63)
|
||||
n := atomic.AddUint64(&h.countAndHotIdx, 1<<63)
|
||||
count := n & ((1 << 63) - 1)
|
||||
// Swap the pointer names to represent the new roles and make
|
||||
// the rest less confusing.
|
||||
hotCounts, coldCounts = coldCounts, hotCounts
|
||||
// Wait for the (new) cold counts to cool down.
|
||||
for count != atomic.LoadUint64(&coldCounts.count) {
|
||||
runtime.Gosched() // Let observations get work done.
|
||||
}
|
||||
// Add all the cold counts to the new hot counts, while merging the cold
|
||||
// buckets into the wider hot buckets, and reset and adjust the cold
|
||||
// counts.
|
||||
// TODO(beorn7): Maybe make it more DRY, cf. Write() method and code
|
||||
// above. Maybe it's too different, though...
|
||||
atomic.AddUint64(&hotCounts.count, count)
|
||||
atomic.StoreUint64(&coldCounts.count, 0)
|
||||
for {
|
||||
hotBits := atomic.LoadUint64(&hotCounts.sumBits)
|
||||
coldBits := atomic.LoadUint64(&coldCounts.sumBits)
|
||||
newBits := math.Float64bits(math.Float64frombits(hotBits) + math.Float64frombits(coldBits))
|
||||
if atomic.CompareAndSwapUint64(&hotCounts.sumBits, hotBits, newBits) {
|
||||
atomic.StoreUint64(&coldCounts.sumBits, 0)
|
||||
break
|
||||
}
|
||||
}
|
||||
for i := range h.upperBounds {
|
||||
atomic.AddUint64(&hotCounts.buckets[i], atomic.LoadUint64(&coldCounts.buckets[i]))
|
||||
atomic.StoreUint64(&coldCounts.buckets[i], 0)
|
||||
}
|
||||
atomic.AddUint64(&hotCounts.sparseZeroBucket, atomic.LoadUint64(&coldCounts.sparseZeroBucket))
|
||||
atomic.StoreUint64(&coldCounts.sparseZeroBucket, 0)
|
||||
|
||||
hot, cold = cold, hot
|
||||
waitForCooldown(count, cold)
|
||||
// Add all the now cold counts to the new hot counts...
|
||||
addAndResetCounts(hot, cold)
|
||||
// ...adjust the schema in the cold counts, too...
|
||||
atomic.StoreInt32(&cold.sparseSchema, coldSchema)
|
||||
// ...and then merge the cold buckets into the wider hot buckets.
|
||||
merge := func(hotBuckets *sync.Map) func(k, v interface{}) bool {
|
||||
return func(k, v interface{}) bool {
|
||||
key := k.(int)
|
||||
|
|
@ -973,19 +927,18 @@ func (h *histogram) limitSparseBuckets(counts *histogramCounts, value float64, b
|
|||
key /= 2
|
||||
// Add to corresponding hot bucket.
|
||||
if addToSparseBucket(hotBuckets, key, atomic.LoadInt64(bucket)) {
|
||||
atomic.AddUint32(&hotCounts.sparseBucketsNumber, 1)
|
||||
atomic.AddUint32(&hot.sparseBucketsNumber, 1)
|
||||
}
|
||||
return true
|
||||
}
|
||||
}
|
||||
|
||||
coldCounts.sparseBucketsPositive.Range(merge(&hotCounts.sparseBucketsPositive))
|
||||
coldCounts.sparseBucketsNegative.Range(merge(&hotCounts.sparseBucketsNegative))
|
||||
atomic.StoreInt32(&coldCounts.sparseSchema, coldSchema)
|
||||
cold.sparseBucketsPositive.Range(merge(&hot.sparseBucketsPositive))
|
||||
cold.sparseBucketsNegative.Range(merge(&hot.sparseBucketsNegative))
|
||||
// Play it simple again and just delete all cold buckets.
|
||||
atomic.StoreUint32(&coldCounts.sparseBucketsNumber, 0)
|
||||
deleteSyncMap(&coldCounts.sparseBucketsNegative)
|
||||
deleteSyncMap(&coldCounts.sparseBucketsPositive)
|
||||
atomic.StoreUint32(&cold.sparseBucketsNumber, 0)
|
||||
deleteSyncMap(&cold.sparseBucketsNegative)
|
||||
deleteSyncMap(&cold.sparseBucketsPositive)
|
||||
}
|
||||
|
||||
func (h *histogram) resetCounts(counts *histogramCounts) {
|
||||
|
|
@ -1385,3 +1338,46 @@ func getLe(key int, schema int32) float64 {
|
|||
exp := (key >> schema) + 1
|
||||
return math.Ldexp(frac, exp)
|
||||
}
|
||||
|
||||
// waitForCooldown returns after the count field in the provided histogramCounts
|
||||
// has reached the provided count value.
|
||||
func waitForCooldown(count uint64, counts *histogramCounts) {
|
||||
for count != atomic.LoadUint64(&counts.count) {
|
||||
runtime.Gosched() // Let observations get work done.
|
||||
}
|
||||
}
|
||||
|
||||
// atomicAddFloat adds the provided float atomically to another float
|
||||
// represented by the bit pattern the bits pointer is pointing to.
|
||||
func atomicAddFloat(bits *uint64, v float64) {
|
||||
for {
|
||||
loadedBits := atomic.LoadUint64(bits)
|
||||
newBits := math.Float64bits(math.Float64frombits(loadedBits) + v)
|
||||
if atomic.CompareAndSwapUint64(bits, loadedBits, newBits) {
|
||||
break
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// atomicDecUint32 atomically decrements the uint32 p points to. See
|
||||
// https://pkg.go.dev/sync/atomic#AddUint32 to understand how this is done.
|
||||
func atomicDecUint32(p *uint32) {
|
||||
atomic.AddUint32(p, ^uint32(0))
|
||||
}
|
||||
|
||||
// addAndResetCounts adds certain fields (count, sum, conventional buckets,
|
||||
// sparse zero bucket) from the cold counts to the corresponding fields in the
|
||||
// hot counts. Those fields are then reset to 0 in the cold counts.
|
||||
func addAndResetCounts(hot, cold *histogramCounts) {
|
||||
atomic.AddUint64(&hot.count, atomic.LoadUint64(&cold.count))
|
||||
atomic.StoreUint64(&cold.count, 0)
|
||||
coldSum := math.Float64frombits(atomic.LoadUint64(&cold.sumBits))
|
||||
atomicAddFloat(&hot.sumBits, coldSum)
|
||||
atomic.StoreUint64(&cold.sumBits, 0)
|
||||
for i := range hot.buckets {
|
||||
atomic.AddUint64(&hot.buckets[i], atomic.LoadUint64(&cold.buckets[i]))
|
||||
atomic.StoreUint64(&cold.buckets[i], 0)
|
||||
}
|
||||
atomic.AddUint64(&hot.sparseZeroBucket, atomic.LoadUint64(&cold.sparseZeroBucket))
|
||||
atomic.StoreUint64(&cold.sparseZeroBucket, 0)
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in New Issue