stats.h

Source: samples/common/core/stats.h

Log2-bucketed histogram and running statistics for latency tracking.

Structs

`Log2Histogram`

Fixed-size histogram with log2-spaced buckets.

Bucket b covers the half-open range [2^(b-1), 2^b) microseconds, with bucket 0 holding the count of zero-valued samples and bucket 63 acting as an overflow bin.

Members

Name	Type	Description
`kBuckets`	`constexpr int`
`buckets`	`uint64_t`

Methods

`Log2Histogram()`

`Reset()`

Zero all bucket counts.

`Add(uint64_t us)`

Record a single sample.

Parameters:

Name	Type	Description
`us`	`uint64_t`	Latency in microseconds.

`Count() const`

Total number of samples recorded across all buckets.

`ApproxPercentile(double pct) const`

Approximate a percentile from the histogram.

Parameters:

Name	Type	Description
`pct`	`double`	Percentile as a fraction in [0.0, 1.0].

Returns: Upper bound of the bucket that contains the target percentile.

`BucketForUs(uint64_t us)`

Compute the bucket index for a given microsecond value.

Parameters:

Name	Type	Description
`us`	`uint64_t`	Latency in microseconds.

Returns: Bucket index in [0, kBuckets).

`RunningStats`

Accumulates min/max/avg/percentile statistics for a stream of microsecond latency samples.

Members

Name	Type	Description
`count`	`uint64_t`
`sum_us`	`uint64_t`
`min_us`	`uint64_t`
`max_us`	`uint64_t`
`hist`	`Log2Histogram`

Methods

`Reset()`

Reset all counters and the histogram.

`Add(uint64_t us)`

Record a single latency sample.

Parameters:

Name	Type	Description
`us`	`uint64_t`	Latency in microseconds.

`AvgMs() const`

Average latency in milliseconds (0.0 if no samples).

`MinMs() const`

Minimum latency in milliseconds.

`MaxMs() const`

Maximum latency in milliseconds.

`P50Ms() const`

Approximate 50th-percentile latency in milliseconds.

`P90Ms() const`

Approximate 90th-percentile latency in milliseconds.

`P99Ms() const`

Approximate 99th-percentile latency in milliseconds.