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// Copyright 2023 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.
// This file contains data types that all implementations of the trace format
// parser need to provide to the rest of the package.
package trace
import (
"fmt"
"math"
"strings"
"internal/trace/v2/event"
"internal/trace/v2/event/go122"
"internal/trace/v2/version"
)
// maxArgs is the maximum number of arguments for "plain" events,
// i.e. anything that could reasonably be represented as a baseEvent.
//
// TODO(mknyszek): This is only 6 instead of 5 because GoStatusStack
// has 5 arguments and needs to smuggle in a 6th. Figure out a way to
// shrink this in the future.
const maxArgs = 6
// timedEventArgs is an array that is able to hold the arguments for any
// timed event.
type timedEventArgs [maxArgs - 1]uint64
// baseEvent is the basic unprocessed event. This serves as a common
// fundamental data structure across.
type baseEvent struct {
typ event.Type
time Time
args timedEventArgs
}
// extra returns a slice representing extra available space in args
// that the parser can use to pass data up into Event.
func (e *baseEvent) extra(v version.Version) []uint64 {
switch v {
case version.Go122:
return e.args[len(go122.Specs()[e.typ].Args)-1:]
}
panic(fmt.Sprintf("unsupported version: go 1.%d", v))
}
// evTable contains the per-generation data necessary to
// interpret an individual event.
type evTable struct {
freq frequency
strings dataTable[stringID, string]
stacks dataTable[stackID, stack]
pcs map[uint64]frame
// extraStrings are strings that get generated during
// parsing but haven't come directly from the trace, so
// they don't appear in strings.
extraStrings []string
extraStringIDs map[string]extraStringID
nextExtra extraStringID
}
// addExtraString adds an extra string to the evTable and returns
// a unique ID for the string in the table.
func (t *evTable) addExtraString(s string) extraStringID {
if s == "" {
return 0
}
if t.extraStringIDs == nil {
t.extraStringIDs = make(map[string]extraStringID)
}
if id, ok := t.extraStringIDs[s]; ok {
return id
}
t.nextExtra++
id := t.nextExtra
t.extraStrings = append(t.extraStrings, s)
t.extraStringIDs[s] = id
return id
}
// getExtraString returns the extra string for the provided ID.
// The ID must have been produced by addExtraString for this evTable.
func (t *evTable) getExtraString(id extraStringID) string {
if id == 0 {
return ""
}
return t.extraStrings[id-1]
}
// dataTable is a mapping from EIs to Es.
type dataTable[EI ~uint64, E any] struct {
present []uint8
dense []E
sparse map[EI]E
}
// insert tries to add a mapping from id to s.
//
// Returns an error if a mapping for id already exists, regardless
// of whether or not s is the same in content. This should be used
// for validation during parsing.
func (d *dataTable[EI, E]) insert(id EI, data E) error {
if d.sparse == nil {
d.sparse = make(map[EI]E)
}
if existing, ok := d.get(id); ok {
return fmt.Errorf("multiple %Ts with the same ID: id=%d, new=%v, existing=%v", data, id, data, existing)
}
d.sparse[id] = data
return nil
}
// compactify attempts to compact sparse into dense.
//
// This is intended to be called only once after insertions are done.
func (d *dataTable[EI, E]) compactify() {
if d.sparse == nil || len(d.dense) != 0 {
// Already compactified.
return
}
// Find the range of IDs.
maxID := EI(0)
minID := ^EI(0)
for id := range d.sparse {
if id > maxID {
maxID = id
}
if id < minID {
minID = id
}
}
if maxID >= math.MaxInt {
// We can't create a slice big enough to hold maxID elements
return
}
// We're willing to waste at most 2x memory.
if int(maxID-minID) > max(len(d.sparse), 2*len(d.sparse)) {
return
}
if int(minID) > len(d.sparse) {
return
}
size := int(maxID) + 1
d.present = make([]uint8, (size+7)/8)
d.dense = make([]E, size)
for id, data := range d.sparse {
d.dense[id] = data
d.present[id/8] |= uint8(1) << (id % 8)
}
d.sparse = nil
}
// get returns the E for id or false if it doesn't
// exist. This should be used for validation during parsing.
func (d *dataTable[EI, E]) get(id EI) (E, bool) {
if id == 0 {
return *new(E), true
}
if uint64(id) < uint64(len(d.dense)) {
if d.present[id/8]&(uint8(1)<<(id%8)) != 0 {
return d.dense[id], true
}
} else if d.sparse != nil {
if data, ok := d.sparse[id]; ok {
return data, true
}
}
return *new(E), false
}
// forEach iterates over all ID/value pairs in the data table.
func (d *dataTable[EI, E]) forEach(yield func(EI, E) bool) bool {
for id, value := range d.dense {
if d.present[id/8]&(uint8(1)<<(id%8)) == 0 {
continue
}
if !yield(EI(id), value) {
return false
}
}
if d.sparse == nil {
return true
}
for id, value := range d.sparse {
if !yield(id, value) {
return false
}
}
return true
}
// mustGet returns the E for id or panics if it fails.
//
// This should only be used if id has already been validated.
func (d *dataTable[EI, E]) mustGet(id EI) E {
data, ok := d.get(id)
if !ok {
panic(fmt.Sprintf("expected id %d in %T table", id, data))
}
return data
}
// frequency is nanoseconds per timestamp unit.
type frequency float64
// mul multiplies an unprocessed to produce a time in nanoseconds.
func (f frequency) mul(t timestamp) Time {
return Time(float64(t) * float64(f))
}
// stringID is an index into the string table for a generation.
type stringID uint64
// extraStringID is an index into the extra string table for a generation.
type extraStringID uint64
// stackID is an index into the stack table for a generation.
type stackID uint64
// cpuSample represents a CPU profiling sample captured by the trace.
type cpuSample struct {
schedCtx
time Time
stack stackID
}
// asEvent produces a complete Event from a cpuSample. It needs
// the evTable from the generation that created it.
//
// We don't just store it as an Event in generation to minimize
// the amount of pointer data floating around.
func (s cpuSample) asEvent(table *evTable) Event {
// TODO(mknyszek): This is go122-specific, but shouldn't be.
// Generalize this in the future.
e := Event{
table: table,
ctx: s.schedCtx,
base: baseEvent{
typ: go122.EvCPUSample,
time: s.time,
},
}
e.base.args[0] = uint64(s.stack)
return e
}
// stack represents a goroutine stack sample.
type stack struct {
pcs []uint64
}
func (s stack) String() string {
var sb strings.Builder
for _, frame := range s.pcs {
fmt.Fprintf(&sb, "\t%#v\n", frame)
}
return sb.String()
}
// frame represents a single stack frame.
type frame struct {
pc uint64
funcID stringID
fileID stringID
line uint64
}