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// Copyright 2022 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package report
import (
"crypto/sha256"
"encoding/binary"
"fmt"
"regexp"
"github.com/google/pprof/internal/measurement"
"github.com/google/pprof/profile"
)
// StackSet holds a set of stacks corresponding to a profile.
//
// Slices in StackSet and the types it contains are always non-nil,
// which makes Javascript code that uses the JSON encoding less error-prone.
type StackSet struct {
Total int64 // Total value of the profile.
Scale float64 // Multiplier to generate displayed value
Type string // Profile type. E.g., "cpu".
Unit string // One of "B", "s", "GCU", or "" (if unknown)
Stacks []Stack // List of stored stacks
Sources []StackSource // Mapping from source index to info
}
// Stack holds a single stack instance.
type Stack struct {
Value int64 // Total value for all samples of this stack.
Sources []int // Indices in StackSet.Sources (callers before callees).
}
// StackSource holds function/location info for a stack entry.
type StackSource struct {
FullName string
FileName string
UniqueName string // Disambiguates functions with same names
Inlined bool // If true this source was inlined into its caller
// Alternative names to display (with decreasing lengths) to make text fit.
// Guaranteed to be non-empty.
Display []string
// Regular expression (anchored) that matches exactly FullName.
RE string
// Places holds the list of stack slots where this source occurs.
// In particular, if [a,b] is an element in Places,
// StackSet.Stacks[a].Sources[b] points to this source.
//
// No stack will be referenced twice in the Places slice for a given
// StackSource. In case of recursion, Places will contain the outer-most
// entry in the recursive stack. E.g., if stack S has source X at positions
// 4,6,9,10, the Places entry for X will contain [S,4].
Places []StackSlot
// Combined count of stacks where this source is the leaf.
Self int64
// Color number to use for this source.
// Colors with high numbers than supported may be treated as zero.
Color int
}
// StackSlot identifies a particular StackSlot.
type StackSlot struct {
Stack int // Index in StackSet.Stacks
Pos int // Index in Stack.Sources
}
// Stacks returns a StackSet for the profile in rpt.
func (rpt *Report) Stacks() StackSet {
// Get scale for converting to default unit of the right type.
scale, unit := measurement.Scale(1, rpt.options.SampleUnit, "default")
if unit == "default" {
unit = ""
}
if rpt.options.Ratio > 0 {
scale *= rpt.options.Ratio
}
s := &StackSet{
Total: rpt.total,
Scale: scale,
Type: rpt.options.SampleType,
Unit: unit,
Stacks: []Stack{}, // Ensure non-nil
Sources: []StackSource{}, // Ensure non-nil
}
s.makeInitialStacks(rpt)
s.fillPlaces()
s.assignColors()
return *s
}
func (s *StackSet) makeInitialStacks(rpt *Report) {
type key struct {
line profile.Line
inlined bool
}
srcs := map[key]int{} // Sources identified so far.
seenFunctions := map[string]bool{}
unknownIndex := 1
getSrc := func(line profile.Line, inlined bool) int {
k := key{line, inlined}
if i, ok := srcs[k]; ok {
return i
}
x := StackSource{Places: []StackSlot{}} // Ensure Places is non-nil
if fn := line.Function; fn != nil {
x.FullName = fn.Name
x.FileName = fn.Filename
if !seenFunctions[fn.Name] {
x.UniqueName = fn.Name
seenFunctions[fn.Name] = true
} else {
// Assign a different name so pivoting picks this function.
x.UniqueName = fmt.Sprint(fn.Name, "#", fn.ID)
}
} else {
x.FullName = fmt.Sprintf("?%d?", unknownIndex)
x.UniqueName = x.FullName
unknownIndex++
}
x.Inlined = inlined
x.RE = "^" + regexp.QuoteMeta(x.UniqueName) + "$"
x.Display = shortNameList(x.FullName)
s.Sources = append(s.Sources, x)
srcs[k] = len(s.Sources) - 1
return len(s.Sources) - 1
}
// Synthesized root location that will be placed at the beginning of each stack.
s.Sources = []StackSource{{
FullName: "root",
Display: []string{"root"},
Places: []StackSlot{},
}}
for _, sample := range rpt.prof.Sample {
value := rpt.options.SampleValue(sample.Value)
stack := Stack{Value: value, Sources: []int{0}} // Start with the root
// Note: we need to reverse the order in the produced stack.
for i := len(sample.Location) - 1; i >= 0; i-- {
loc := sample.Location[i]
for j := len(loc.Line) - 1; j >= 0; j-- {
line := loc.Line[j]
inlined := (j != len(loc.Line)-1)
stack.Sources = append(stack.Sources, getSrc(line, inlined))
}
}
leaf := stack.Sources[len(stack.Sources)-1]
s.Sources[leaf].Self += value
s.Stacks = append(s.Stacks, stack)
}
}
func (s *StackSet) fillPlaces() {
for i, stack := range s.Stacks {
seenSrcs := map[int]bool{}
for j, src := range stack.Sources {
if seenSrcs[src] {
continue
}
seenSrcs[src] = true
s.Sources[src].Places = append(s.Sources[src].Places, StackSlot{i, j})
}
}
}
func (s *StackSet) assignColors() {
// Assign different color indices to different packages.
const numColors = 1048576
for i, src := range s.Sources {
pkg := packageName(src.FullName)
h := sha256.Sum256([]byte(pkg))
index := binary.LittleEndian.Uint32(h[:])
s.Sources[i].Color = int(index % numColors)
}
}