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Set time and duration of profile #18

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merged 6 commits into from
Aug 27, 2022
Merged

Set time and duration of profile #18

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1b4aea8
Set time and duration of profile
brancz Apr 27, 2022
51ce0f2
Merge remote-tracking branch 'origin/master' into set-time-duration
felixge Aug 27, 2022
b6b7c93
fix: use monotonic clock to calculate duration
felixge Aug 27, 2022
c6e1fcf
Merge remote-tracking branch 'origin/master' into set-time-duration
felixge Aug 27, 2022
22340eb
fix test after merging master
felixge Aug 27, 2022
1bcfc77
fix test to work in all time zones
felixge Aug 27, 2022
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12 changes: 11 additions & 1 deletion fgprof.go
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,8 @@ import (
// that needs to be invoked by the caller to stop the profiling and write the
// results to w using the given format.
func Start(w io.Writer, format Format) func() error {
startTime := time.Now()

// Go's CPU profiler uses 100hz, but 99hz might be less likely to result in
// accidental synchronization with the program we're profiling.
const hz = 99
Expand All @@ -39,7 +41,15 @@ func Start(w io.Writer, format Format) func() error {

return func() error {
stopCh <- struct{}{}
return writeFormat(w, stackCounts.HumanMap(prof.SelfFrame()), format, hz)
endTime := time.Now()
return writeFormat(
w,
stackCounts.HumanMap(prof.SelfFrame()),
format,
hz,
startTime,
endTime,
)
}
}

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9 changes: 6 additions & 3 deletions format.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ import (
"io"
"sort"
"strings"
"time"

"github.com/google/pprof/profile"
)
Expand All @@ -21,12 +22,12 @@ const (
FormatPprof Format = "pprof"
)

func writeFormat(w io.Writer, s map[string]int, f Format, hz int) error {
func writeFormat(w io.Writer, s map[string]int, f Format, hz int, startTime, endTime time.Time) error {
switch f {
case FormatFolded:
return writeFolded(w, s)
case FormatPprof:
return toPprof(s, hz).Write(w)
return toPprof(s, hz, startTime, endTime).Write(w)
default:
return fmt.Errorf("unknown format: %q", f)
}
Expand All @@ -42,14 +43,16 @@ func writeFolded(w io.Writer, s map[string]int) error {
return nil
}

func toPprof(s map[string]int, hz int) *profile.Profile {
func toPprof(s map[string]int, hz int, startTime, endTime time.Time) *profile.Profile {
functionID := uint64(1)
locationID := uint64(1)
line := int64(1)

p := &profile.Profile{}
m := &profile.Mapping{ID: 1, HasFunctions: true}
p.Period = int64(1e9 / hz) // Number of nanoseconds between samples.
p.TimeNanos = startTime.UnixNano()
p.DurationNanos = endTime.UnixNano() - p.TimeNanos
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🐞 This is going to produce incorrect results when clock changes or leap seconds are involved. I'll push a fix.

p.Mapping = []*profile.Mapping{m}
p.SampleType = []*profile.ValueType{
{
Expand Down