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// Copyright 2014 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 graph represents a pprof profile as a directed graph.
//
// This package is a simplified fork of github.com/google/pprof/internal/graph.
package graph
import (
"fmt"
"internal/profile"
"sort"
"strings"
)
// Options encodes the options for constructing a graph
type Options struct {
SampleValue func(s []int64) int64 // Function to compute the value of a sample
SampleMeanDivisor func(s []int64) int64 // Function to compute the divisor for mean graphs, or nil
DropNegative bool // Drop nodes with overall negative values
KeptNodes NodeSet // If non-nil, only use nodes in this set
}
// Nodes is an ordered collection of graph nodes.
type Nodes []*Node
// Node is an entry on a profiling report. It represents a unique
// program location.
type Node struct {
// Info describes the source location associated to this node.
Info NodeInfo
// Function represents the function that this node belongs to. On
// graphs with sub-function resolution (eg line number or
// addresses), two nodes in a NodeMap that are part of the same
// function have the same value of Node.Function. If the Node
// represents the whole function, it points back to itself.
Function *Node
// Values associated to this node. Flat is exclusive to this node,
// Cum includes all descendents.
Flat, FlatDiv, Cum, CumDiv int64
// In and out Contains the nodes immediately reaching or reached by
// this node.
In, Out EdgeMap
}
// Graph summarizes a performance profile into a format that is
// suitable for visualization.
type Graph struct {
Nodes Nodes
}
// FlatValue returns the exclusive value for this node, computing the
// mean if a divisor is available.
func (n *Node) FlatValue() int64 {
if n.FlatDiv == 0 {
return n.Flat
}
return n.Flat / n.FlatDiv
}
// CumValue returns the inclusive value for this node, computing the
// mean if a divisor is available.
func (n *Node) CumValue() int64 {
if n.CumDiv == 0 {
return n.Cum
}
return n.Cum / n.CumDiv
}
// AddToEdge increases the weight of an edge between two nodes. If
// there isn't such an edge one is created.
func (n *Node) AddToEdge(to *Node, v int64, residual, inline bool) {
n.AddToEdgeDiv(to, 0, v, residual, inline)
}
// AddToEdgeDiv increases the weight of an edge between two nodes. If
// there isn't such an edge one is created.
func (n *Node) AddToEdgeDiv(to *Node, dv, v int64, residual, inline bool) {
if e := n.Out.FindTo(to); e != nil {
e.WeightDiv += dv
e.Weight += v
if residual {
e.Residual = true
}
if !inline {
e.Inline = false
}
return
}
info := &Edge{Src: n, Dest: to, WeightDiv: dv, Weight: v, Residual: residual, Inline: inline}
n.Out.Add(info)
to.In.Add(info)
}
// NodeInfo contains the attributes for a node.
type NodeInfo struct {
Name string
Address uint64
StartLine, Lineno int
}
// PrintableName calls the Node's Formatter function with a single space separator.
func (i *NodeInfo) PrintableName() string {
return strings.Join(i.NameComponents(), " ")
}
// NameComponents returns the components of the printable name to be used for a node.
func (i *NodeInfo) NameComponents() []string {
var name []string
if i.Address != 0 {
name = append(name, fmt.Sprintf("%016x", i.Address))
}
if fun := i.Name; fun != "" {
name = append(name, fun)
}
switch {
case i.Lineno != 0:
// User requested line numbers, provide what we have.
name = append(name, fmt.Sprintf(":%d", i.Lineno))
case i.Name != "":
// User requested function name. It was already included.
default:
// Do not leave it empty if there is no information at all.
name = append(name, "<unknown>")
}
return name
}
// NodeMap maps from a node info struct to a node. It is used to merge
// report entries with the same info.
type NodeMap map[NodeInfo]*Node
// NodeSet is a collection of node info structs.
type NodeSet map[NodeInfo]bool
// NodePtrSet is a collection of nodes. Trimming a graph or tree requires a set
// of objects which uniquely identify the nodes to keep. In a graph, NodeInfo
// works as a unique identifier; however, in a tree multiple nodes may share
// identical NodeInfos. A *Node does uniquely identify a node so we can use that
// instead. Though a *Node also uniquely identifies a node in a graph,
// currently, during trimming, graphs are rebuilt from scratch using only the
// NodeSet, so there would not be the required context of the initial graph to
// allow for the use of *Node.
type NodePtrSet map[*Node]bool
// FindOrInsertNode takes the info for a node and either returns a matching node
// from the node map if one exists, or adds one to the map if one does not.
// If kept is non-nil, nodes are only added if they can be located on it.
func (nm NodeMap) FindOrInsertNode(info NodeInfo, kept NodeSet) *Node {
if kept != nil {
if _, ok := kept[info]; !ok {
return nil
}
}
if n, ok := nm[info]; ok {
return n
}
n := &Node{
Info: info,
}
nm[info] = n
if info.Address == 0 && info.Lineno == 0 {
// This node represents the whole function, so point Function
// back to itself.
n.Function = n
return n
}
// Find a node that represents the whole function.
info.Address = 0
info.Lineno = 0
n.Function = nm.FindOrInsertNode(info, nil)
return n
}
// EdgeMap is used to represent the incoming/outgoing edges from a node.
type EdgeMap []*Edge
func (em EdgeMap) FindTo(n *Node) *Edge {
for _, e := range em {
if e.Dest == n {
return e
}
}
return nil
}
func (em *EdgeMap) Add(e *Edge) {
*em = append(*em, e)
}
func (em *EdgeMap) Delete(e *Edge) {
for i, edge := range *em {
if edge == e {
(*em)[i] = (*em)[len(*em)-1]
*em = (*em)[:len(*em)-1]
return
}
}
}
// Edge contains any attributes to be represented about edges in a graph.
type Edge struct {
Src, Dest *Node
// The summary weight of the edge
Weight, WeightDiv int64
// residual edges connect nodes that were connected through a
// separate node, which has been removed from the report.
Residual bool
// An inline edge represents a call that was inlined into the caller.
Inline bool
}
// WeightValue returns the weight value for this edge, normalizing if a
// divisor is available.
func (e *Edge) WeightValue() int64 {
if e.WeightDiv == 0 {
return e.Weight
}
return e.Weight / e.WeightDiv
}
// NewGraph computes a graph from a profile.
func NewGraph(prof *profile.Profile, o *Options) *Graph {
nodes, locationMap := CreateNodes(prof, o)
seenNode := make(map[*Node]bool)
seenEdge := make(map[nodePair]bool)
for _, sample := range prof.Sample {
var w, dw int64
w = o.SampleValue(sample.Value)
if o.SampleMeanDivisor != nil {
dw = o.SampleMeanDivisor(sample.Value)
}
if dw == 0 && w == 0 {
continue
}
for k := range seenNode {
delete(seenNode, k)
}
for k := range seenEdge {
delete(seenEdge, k)
}
var parent *Node
// A residual edge goes over one or more nodes that were not kept.
residual := false
// Group the sample frames, based on a global map.
// Count only the last two frames as a call edge. Frames higher up
// the stack are unlikely to be repeated calls (e.g. runtime.main
// calling main.main). So adding weights to call edges higher up
// the stack may be not reflecting the actual call edge weights
// in the program. Without a branch profile this is just an
// approximation.
i := 1
if last := len(sample.Location) - 1; last < i {
i = last
}
for ; i >= 0; i-- {
l := sample.Location[i]
locNodes := locationMap.get(l.ID)
for ni := len(locNodes) - 1; ni >= 0; ni-- {
n := locNodes[ni]
if n == nil {
residual = true
continue
}
// Add cum weight to all nodes in stack, avoiding double counting.
_, sawNode := seenNode[n]
if !sawNode {
seenNode[n] = true
n.addSample(dw, w, false)
}
// Update edge weights for all edges in stack, avoiding double counting.
if (!sawNode || !seenEdge[nodePair{n, parent}]) && parent != nil && n != parent {
seenEdge[nodePair{n, parent}] = true
parent.AddToEdgeDiv(n, dw, w, residual, ni != len(locNodes)-1)
}
parent = n
residual = false
}
}
if parent != nil && !residual {
// Add flat weight to leaf node.
parent.addSample(dw, w, true)
}
}
return selectNodesForGraph(nodes, o.DropNegative)
}
func selectNodesForGraph(nodes Nodes, dropNegative bool) *Graph {
// Collect nodes into a graph.
gNodes := make(Nodes, 0, len(nodes))
for _, n := range nodes {
if n == nil {
continue
}
if n.Cum == 0 && n.Flat == 0 {
continue
}
if dropNegative && isNegative(n) {
continue
}
gNodes = append(gNodes, n)
}
return &Graph{gNodes}
}
type nodePair struct {
src, dest *Node
}
// isNegative returns true if the node is considered as "negative" for the
// purposes of drop_negative.
func isNegative(n *Node) bool {
switch {
case n.Flat < 0:
return true
case n.Flat == 0 && n.Cum < 0:
return true
default:
return false
}
}
type locationMap struct {
s []Nodes // a slice for small sequential IDs
m map[uint64]Nodes // fallback for large IDs (unlikely)
}
func (l *locationMap) add(id uint64, n Nodes) {
if id < uint64(len(l.s)) {
l.s[id] = n
} else {
l.m[id] = n
}
}
func (l locationMap) get(id uint64) Nodes {
if id < uint64(len(l.s)) {
return l.s[id]
} else {
return l.m[id]
}
}
// CreateNodes creates graph nodes for all locations in a profile. It
// returns set of all nodes, plus a mapping of each location to the
// set of corresponding nodes (one per location.Line).
func CreateNodes(prof *profile.Profile, o *Options) (Nodes, locationMap) {
locations := locationMap{make([]Nodes, len(prof.Location)+1), make(map[uint64]Nodes)}
nm := make(NodeMap, len(prof.Location))
for _, l := range prof.Location {
lines := l.Line
if len(lines) == 0 {
lines = []profile.Line{{}} // Create empty line to include location info.
}
nodes := make(Nodes, len(lines))
for ln := range lines {
nodes[ln] = nm.findOrInsertLine(l, lines[ln], o)
}
locations.add(l.ID, nodes)
}
return nm.nodes(), locations
}
func (nm NodeMap) nodes() Nodes {
nodes := make(Nodes, 0, len(nm))
for _, n := range nm {
nodes = append(nodes, n)
}
return nodes
}
func (nm NodeMap) findOrInsertLine(l *profile.Location, li profile.Line, o *Options) *Node {
var objfile string
if m := l.Mapping; m != nil && m.File != "" {
objfile = m.File
}
if ni := nodeInfo(l, li, objfile, o); ni != nil {
return nm.FindOrInsertNode(*ni, o.KeptNodes)
}
return nil
}
func nodeInfo(l *profile.Location, line profile.Line, objfile string, o *Options) *NodeInfo {
if line.Function == nil {
return &NodeInfo{Address: l.Address}
}
ni := &NodeInfo{
Address: l.Address,
Lineno: int(line.Line),
Name: line.Function.Name,
}
ni.StartLine = int(line.Function.StartLine)
return ni
}
// Sum adds the flat and cum values of a set of nodes.
func (ns Nodes) Sum() (flat int64, cum int64) {
for _, n := range ns {
flat += n.Flat
cum += n.Cum
}
return
}
func (n *Node) addSample(dw, w int64, flat bool) {
// Update sample value
if flat {
n.FlatDiv += dw
n.Flat += w
} else {
n.CumDiv += dw
n.Cum += w
}
}
// String returns a text representation of a graph, for debugging purposes.
func (g *Graph) String() string {
var s []string
nodeIndex := make(map[*Node]int, len(g.Nodes))
for i, n := range g.Nodes {
nodeIndex[n] = i + 1
}
for i, n := range g.Nodes {
name := n.Info.PrintableName()
var in, out []int
for _, from := range n.In {
in = append(in, nodeIndex[from.Src])
}
for _, to := range n.Out {
out = append(out, nodeIndex[to.Dest])
}
s = append(s, fmt.Sprintf("%d: %s[flat=%d cum=%d] %x -> %v ", i+1, name, n.Flat, n.Cum, in, out))
}
return strings.Join(s, "\n")
}
// Sort returns a slice of the edges in the map, in a consistent
// order. The sort order is first based on the edge weight
// (higher-to-lower) and then by the node names to avoid flakiness.
func (e EdgeMap) Sort() []*Edge {
el := make(edgeList, 0, len(e))
for _, w := range e {
el = append(el, w)
}
sort.Sort(el)
return el
}
// Sum returns the total weight for a set of nodes.
func (e EdgeMap) Sum() int64 {
var ret int64
for _, edge := range e {
ret += edge.Weight
}
return ret
}
type edgeList []*Edge
func (el edgeList) Len() int {
return len(el)
}
func (el edgeList) Less(i, j int) bool {
if el[i].Weight != el[j].Weight {
return abs64(el[i].Weight) > abs64(el[j].Weight)
}
from1 := el[i].Src.Info.PrintableName()
from2 := el[j].Src.Info.PrintableName()
if from1 != from2 {
return from1 < from2
}
to1 := el[i].Dest.Info.PrintableName()
to2 := el[j].Dest.Info.PrintableName()
return to1 < to2
}
func (el edgeList) Swap(i, j int) {
el[i], el[j] = el[j], el[i]
}
func abs64(i int64) int64 {
if i < 0 {
return -i
}
return i
}