From 2aa4340551c4ce95ce0c9f8ef2d752ba58bb8ba6 Mon Sep 17 00:00:00 2001
From: Jakob Borg <jakob@nym.se>
Date: Wed, 23 Jul 2014 13:17:34 +0200
Subject: [PATCH] Add performance stats collection

---
 .gitignore                 |  3 +++
 cmd/syncthing/perfstats.go | 45 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)
 create mode 100644 cmd/syncthing/perfstats.go

diff --git a/.gitignore b/.gitignore
index 87d89c549..0fe8557aa 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,6 @@ discosrv
 .jshintrc
 coverage.out
 files/pidx
+discosrv.exe
+bin
+perfstats*.csv
diff --git a/cmd/syncthing/perfstats.go b/cmd/syncthing/perfstats.go
new file mode 100644
index 000000000..8711a64af
--- /dev/null
+++ b/cmd/syncthing/perfstats.go
@@ -0,0 +1,45 @@
+// +build perfstats
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+	"syscall"
+	"time"
+)
+
+func init() {
+	go savePerfStats(fmt.Sprintf("perfstats-%d.csv", syscall.Getpid()))
+}
+
+func savePerfStats(file string) {
+	fd, err := os.Create(file)
+	if err != nil {
+		panic(err)
+	}
+
+	var prevUsage int64
+	var prevTime int64
+	var rusage syscall.Rusage
+	var memstats runtime.MemStats
+
+	t0 := time.Now()
+	for t := range time.NewTicker(250 * time.Millisecond).C {
+		syscall.Getrusage(syscall.RUSAGE_SELF, &rusage)
+		curTime := time.Now().UnixNano()
+		timeDiff := curTime - prevTime
+		curUsage := rusage.Utime.Nano() + rusage.Stime.Nano()
+		usageDiff := curUsage - prevUsage
+		cpuUsagePercent := 100 * float64(usageDiff) / float64(timeDiff)
+		prevTime = curTime
+		prevUsage = curUsage
+
+		runtime.ReadMemStats(&memstats)
+
+		startms := int(t.Sub(t0).Seconds() * 1000)
+
+		fmt.Fprintf(fd, "%d\t%f\t%d\t%d\n", startms, cpuUsagePercent, memstats.Alloc, memstats.Sys)
+	}
+}