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// Copyright 2016 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 pprof
import (
"io"
"math"
"runtime"
"strings"
)
// writeHeapProto writes the current heap profile in protobuf format to w.
func writeHeapProto(w io.Writer, p []runtime.MemProfileRecord, rate int64, defaultSampleType string) error {
b := newProfileBuilder(w)
b.pbValueType(tagProfile_PeriodType, "space", "bytes")
b.pb.int64Opt(tagProfile_Period, rate)
b.pbValueType(tagProfile_SampleType, "alloc_objects", "count")
b.pbValueType(tagProfile_SampleType, "alloc_space", "bytes")
b.pbValueType(tagProfile_SampleType, "inuse_objects", "count")
b.pbValueType(tagProfile_SampleType, "inuse_space", "bytes")
if defaultSampleType != "" {
b.pb.int64Opt(tagProfile_DefaultSampleType, b.stringIndex(defaultSampleType))
}
values := []int64{0, 0, 0, 0}
var locs []uint64
for _, r := range p {
hideRuntime := true
for tries := 0; tries < 2; tries++ {
stk := r.Stack()
// For heap profiles, all stack
// addresses are return PCs, which is
// what appendLocsForStack expects.
if hideRuntime {
for i, addr := range stk {
if f := runtime.FuncForPC(addr); f != nil && strings.HasPrefix(f.Name(), "runtime.") {
continue
}
// Found non-runtime. Show any runtime uses above it.
stk = stk[i:]
break
}
}
locs = b.appendLocsForStack(locs[:0], stk)
if len(locs) > 0 {
break
}
hideRuntime = false // try again, and show all frames next time.
}
values[0], values[1] = scaleHeapSample(r.AllocObjects, r.AllocBytes, rate)
values[2], values[3] = scaleHeapSample(r.InUseObjects(), r.InUseBytes(), rate)
var blockSize int64
if r.AllocObjects > 0 {
blockSize = r.AllocBytes / r.AllocObjects
}
b.pbSample(values, locs, func() {
if blockSize != 0 {
b.pbLabel(tagSample_Label, "bytes", "", blockSize)
}
})
}
b.build()
return nil
}
// scaleHeapSample adjusts the data from a heap Sample to
// account for its probability of appearing in the collected
// data. heap profiles are a sampling of the memory allocations
// requests in a program. We estimate the unsampled value by dividing
// each collected sample by its probability of appearing in the
// profile. heap profiles rely on a poisson process to determine
// which samples to collect, based on the desired average collection
// rate R. The probability of a sample of size S to appear in that
// profile is 1-exp(-S/R).
func scaleHeapSample(count, size, rate int64) (int64, int64) {
if count == 0 || size == 0 {
return 0, 0
}
if rate <= 1 {
// if rate==1 all samples were collected so no adjustment is needed.
// if rate<1 treat as unknown and skip scaling.
return count, size
}
avgSize := float64(size) / float64(count)
scale := 1 / (1 - math.Exp(-avgSize/float64(rate)))
return int64(float64(count) * scale), int64(float64(size) * scale)
}
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