Add STBLOCKPROFILE

cmd/syncthing/blockprof.go

@@ -0,0 +1,59 @@
+// Copyright (C) 2014 The Syncthing Authors.
+//
+// This program is free software: you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+//
+// This program is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+// more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program. If not, see <http://www.gnu.org/licenses/>.
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+	"runtime/pprof"
+	"syscall"
+	"time"
+)
+
+func init() {
+	if innerProcess && os.Getenv("STBLOCKPROFILE") != "" {
+		profiler := pprof.Lookup("block")
+		if profiler == nil {
+			panic("Couldn't find block profiler")
+		}
+		l.Debugln("Starting block profiling")
+		go saveBlockingProfiles(profiler)
+	}
+}
+
+func saveBlockingProfiles(profiler *pprof.Profile) {
+	runtime.SetBlockProfileRate(1)
+
+	t0 := time.Now()
+	for t := range time.NewTicker(20 * time.Second).C {
+		startms := int(t.Sub(t0).Seconds() * 1000)
+
+		fd, err := os.Create(fmt.Sprintf("block-%05d-%07d.pprof", syscall.Getpid(), startms))
+		if err != nil {
+			panic(err)
+		}
+		err = profiler.WriteTo(fd, 0)
+		if err != nil {
+			panic(err)
+		}
+		err = fd.Close()
+		if err != nil {
+			panic(err)
+		}
+
+	}
+}

cmd/syncthing/main.go

@@ -167,6 +167,9 @@ are mostly useful for developers. Use with care.
  STHEAPPROFILE   Write heap profiles to heap-$pid-$timestamp.pprof each time
                  heap usage increases.
 
+ STBLOCKPROFILE  Write block profiles to block-$pid-$timestamp.pprof every 20
+                 seconds.
+
  STPERFSTATS     Write running performance statistics to perf-$pid.csv. Not
                  supported on Windows.