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Add memory sampler to look at average mem stats #156

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Merged
zix99 merged 1 commit into from
Oct 26, 2025
Merged

Add memory sampler to look at average mem stats #156

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67 changes: 60 additions & 7 deletions profiling.go
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ import (
"os"
"runtime"
"runtime/pprof"
"sync"
"time"

"github.com/urfave/cli/v2"
Expand Down Expand Up @@ -42,6 +43,48 @@ func stopProfile() {
profilerDone <- true
}

func startMemoryRecorder() (stop func()) {
var samples int64
var peakHeap, peakAlloc, peakStack uint64
var avgHeap, avgAlloc, avgStack int64

var wg sync.WaitGroup
doneSignal := make(chan struct{})

wg.Add(1)
go func() {
defer wg.Done()

var stats runtime.MemStats
OUTER_LOOP:
for {
select {
case <-time.After(100 * time.Millisecond):
runtime.ReadMemStats(&stats)

samples++
peakHeap = max(peakHeap, stats.HeapInuse)
avgHeap += (int64(stats.HeapInuse) - avgHeap) / samples

peakAlloc = max(peakAlloc, stats.HeapAlloc)
avgAlloc = max(int64(stats.HeapAlloc)-avgAlloc) / samples

peakStack = max(peakStack, stats.StackInuse)
avgStack += (int64(stats.StackInuse) - avgStack) / samples
case <-doneSignal:
break OUTER_LOOP
}
}

fmt.Fprintf(os.Stderr, "MemStat: samples=%d, peakHeap=%d, avgHeap=%d, peakAlloc=%d, avgAlloc=%d, peakStack=%d, avgStack=%d\n", samples, peakHeap, avgHeap, peakAlloc, avgAlloc, peakStack, avgStack)
}()

return func() {
doneSignal <- struct{}{}
wg.Wait()
}
}

func init() {
appModifiers = append(appModifiers, func(app *cli.App) {
app.Flags = append(app.Flags, &cli.StringFlag{
Expand All @@ -50,10 +93,14 @@ func init() {
}, &cli.BoolFlag{
Name: "metrics",
Usage: "Outputs runtime memory metrics after a program runs",
}, &cli.BoolFlag{
Name: "metrics-memory",
Usage: "Records memory metrics every 100ms to get peaks/averages",
})

var beforeMem runtime.MemStats
var startMem runtime.MemStats
var start time.Time
var memRecordStop func()

oldBefore := app.Before
app.Before = func(c *cli.Context) error {
Expand All @@ -62,7 +109,10 @@ func init() {
startProfiler(basename)
}
if c.Bool("metrics") {
runtime.ReadMemStats(&beforeMem)
runtime.ReadMemStats(&startMem)
}
if c.Bool("metrics-memory") {
memRecordStop = startMemoryRecorder()
}

start = time.Now()
Expand All @@ -82,11 +132,14 @@ func init() {
runtime.ReadMemStats(&after)
fmt.Fprintf(os.Stderr, "Runtime: %s\n", stop.Sub(start).String())
fmt.Fprintf(os.Stderr, "Memory : total=%d; malloc=%d; free=%d; numgc=%d; pausegc=%s\n",
after.TotalAlloc-beforeMem.TotalAlloc,
after.Mallocs-beforeMem.Mallocs,
after.Frees-beforeMem.Frees,
after.NumGC-beforeMem.NumGC,
time.Duration(after.PauseTotalNs-beforeMem.PauseTotalNs).String())
after.TotalAlloc-startMem.TotalAlloc,
after.Mallocs-startMem.Mallocs,
after.Frees-startMem.Frees,
after.NumGC-startMem.NumGC,
time.Duration(after.PauseTotalNs-startMem.PauseTotalNs).String())
}
if memRecordStop != nil {
memRecordStop()
}
if c.IsSet("profile") {
stopProfile()
Expand Down
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