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cmd/compile/internal/pgo: use a slice for locations

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Currently locations are stored in a map and looked up by ID from
the map. The IDs are usually small sequential integers (the Go
pprof CPU profiles are so). Using a slice is more efficient (with
a fallback map to handle weirdly large IDs).

Change-Id: I9e20d5cebca3a5239636413e1bf2f0b273038031
Reviewed-on: https://go-review.googlesource.com/c/go/+/447803
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Cherry Mui 2022-11-03 21:11:23 -04:00
parent 6d58aea5d4
commit d9cc39b25c
2 changed files with 29 additions and 10 deletions
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37
src/cmd/compile/internal/pgo/graph.go
View file

@ -245,10 +245,8 @@ func (e *Edge) WeightValue() int64 {
return e.Weight / e.WeightDiv
}
// newGraph computes a graph from a profile. It returns the graph, and
// a map from the profile location indices to the corresponding graph
// nodes.
func newGraph(prof *profile.Profile, o *Options) (*Graph, map[uint64]Nodes) {
// 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)
@ -274,7 +272,7 @@ func newGraph(prof *profile.Profile, o *Options) (*Graph, map[uint64]Nodes) {
// Group the sample frames, based on a global map.
for i := len(sample.Location) - 1; i >= 0; i-- {
l := sample.Location[i]
locNodes := locationMap[l.ID]
locNodes := locationMap.get(l.ID)
for ni := len(locNodes) - 1; ni >= 0; ni-- {
n := locNodes[ni]
if n == nil {
@ -303,7 +301,7 @@ func newGraph(prof *profile.Profile, o *Options) (*Graph, map[uint64]Nodes) {
}
}
return selectNodesForGraph(nodes, o.DropNegative), locationMap
return selectNodesForGraph(nodes, o.DropNegative)
}
func selectNodesForGraph(nodes Nodes, dropNegative bool) *Graph {
@ -389,11 +387,32 @@ func isNegative(n *Node) bool {
}
}
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, map[uint64]Nodes) {
locations := make(map[uint64]Nodes, len(prof.Location))
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
@ -404,7 +423,7 @@ func CreateNodes(prof *profile.Profile, o *Options) (Nodes, map[uint64]Nodes) {
for ln := range lines {
nodes[ln] = nm.findOrInsertLine(l, lines[ln], o)
}
locations[l.ID] = nodes
locations.add(l.ID, nodes)
}
return nm.nodes(), locations
}

2
src/cmd/compile/internal/pgo/irgraph.go
View file

@ -140,7 +140,7 @@ func New(profileFile string) *Profile {
return nil
}
g, _ := newGraph(profile, &Options{
g := newGraph(profile, &Options{
CallTree: false,
SampleValue: func(v []int64) int64 { return v[1] },
})