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