diff options
Diffstat (limited to 'src/runtime/histogram.go')
| -rw-r--r-- | src/runtime/histogram.go | 52 |
1 files changed, 23 insertions, 29 deletions
diff --git a/src/runtime/histogram.go b/src/runtime/histogram.go index da4910d341c..1b45ad97df3 100644 --- a/src/runtime/histogram.go +++ b/src/runtime/histogram.go @@ -47,7 +47,7 @@ const ( // │ └---- Next 4 bits -> sub-bucket 1 // └------- Bit 5 set -> super-bucket 2 // - // Following this pattern, bucket 45 will have the bit 48 set. We don't + // Following this pattern, super-bucket 44 will have the bit 47 set. We don't // have any buckets for higher values, so the highest sub-bucket will // contain values of 2^48-1 nanoseconds or approx. 3 days. This range is // more than enough to handle durations produced by the runtime. @@ -135,36 +135,30 @@ func float64NegInf() float64 { func timeHistogramMetricsBuckets() []float64 { b := make([]float64, timeHistTotalBuckets+1) b[0] = float64NegInf() - for i := 0; i < timeHistNumSuperBuckets; i++ { - superBucketMin := uint64(0) - // The (inclusive) minimum for the first non-negative bucket is 0. - if i > 0 { - // The minimum for the second bucket will be - // 1 << timeHistSubBucketBits, indicating that all - // sub-buckets are represented by the next timeHistSubBucketBits - // bits. - // Thereafter, we shift up by 1 each time, so we can represent - // this pattern as (i-1)+timeHistSubBucketBits. - superBucketMin = uint64(1) << uint(i-1+timeHistSubBucketBits) - } - // subBucketShift is the amount that we need to shift the sub-bucket - // index to combine it with the bucketMin. - subBucketShift := uint(0) - if i > 1 { - // The first two super buckets are exact with respect to integers, - // so we'll never have to shift the sub-bucket index. Thereafter, - // we shift up by 1 with each subsequent bucket. - subBucketShift = uint(i - 2) - } + // Super-bucket 0 has no bits above timeHistSubBucketBits + // set, so just iterate over each bucket and assign the + // incrementing bucket. + for i := 0; i < timeHistNumSubBuckets; i++ { + bucketNanos := uint64(i) + b[i+1] = float64(bucketNanos) / 1e9 + } + // Generate the rest of the super-buckets. It's easier to reason + // about if we cut out the 0'th bucket, so subtract one since + // we just handled that bucket. + for i := 0; i < timeHistNumSuperBuckets-1; i++ { for j := 0; j < timeHistNumSubBuckets; j++ { - // j is the sub-bucket index. By shifting the index into position to - // combine with the bucket minimum, we obtain the minimum value for that - // sub-bucket. - subBucketMin := superBucketMin + (uint64(j) << subBucketShift) - - // Convert the subBucketMin which is in nanoseconds to a float64 seconds value. + // Set the super-bucket bit. + bucketNanos := uint64(1) << (i + timeHistSubBucketBits) + // Set the sub-bucket bits. + bucketNanos |= uint64(j) << i + // The index for this bucket is going to be the (i+1)'th super bucket + // (note that we're starting from zero, but handled the first super-bucket + // earlier, so we need to compensate), and the j'th sub bucket. + // Add 1 because we left space for -Inf. + bucketIndex := (i+1)*timeHistNumSubBuckets + j + 1 + // Convert nanoseconds to seconds via a division. // These values will all be exactly representable by a float64. - b[i*timeHistNumSubBuckets+j+1] = float64(subBucketMin) / 1e9 + b[bucketIndex] = float64(bucketNanos) / 1e9 } } b[len(b)-1] = float64Inf() |