golang sample 代码
文件路径：/src/runtime/metrics/sample.go
/ Copyright 2020 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
package metrics
import (
_ "runtime" / depends on the runtime via a linkname'd function
"unsafe"
)
/ Sample captures a single metric sample.
type Sample struct {
/ Name is the name of the metric sampled.
/
/ It must correspond to a name in one of the metric descriptions
/ returned by All.
Name string
/ Value is the value of the metric sample.
Value Value
}
/ Implemented in the runtime.
func runtime_readMetrics(unsafe.Pointer, int, int)
/ Read populates each Value field in the given slice of metric samples.
/
/ Desired metrics should be present in the slice with the appropriate name.
/ The user of this API is encouraged to re-use the same slice between calls for
/ efficiency, but is not required to do so.
/
/ Note that re-use has some caveats. Notably, Values should not be read or
/ manipulated while a Read with that value is outstanding; that is a data race.
/ This property includes pointer-typed Values (for example, Float64Histogram)
/ whose underlying storage will be reused by Read when possible. To safely use
/ such values in a concurrent setting, all data must be deep-copied.
/
/ It is safe to execute multiple Read calls concurrently, but their arguments
/ must share no underlying memory. When in doubt, create a new []Sample from
/ scratch, which is always safe, though may be inefficient.
/
/ Sample values with names not appearing in All will have their Value populated
/ as KindBad to indicate that the name is unknown.
func Read(m []Sample) {
runtime_readMetrics(unsafe.Pointer(&m[0]), len(m), cap(m))
}