diff --git a/cmd/tsdb/main.go b/cmd/tsdb/main.go
index 16b73744f..437f4ce8f 100644
--- a/cmd/tsdb/main.go
+++ b/cmd/tsdb/main.go
@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"net/http"
+	_ "net/http/pprof"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -21,6 +23,9 @@ import (
 )
 
 func main() {
+	// Start HTTP server for pprof endpoint.
+	go http.ListenAndServe(":9999", nil)
+
 	root := &cobra.Command{
 		Use:   "tsdb",
 		Short: "CLI tool for tsdb",
diff --git a/db.go b/db.go
index 78d226833..064dd2e2a 100644
--- a/db.go
+++ b/db.go
@@ -229,6 +229,7 @@ func (db *DB) compact() error {
 
 			select {
 			case <-db.stopc:
+				db.mtx.RUnlock()
 				return nil
 			default:
 			}
diff --git a/wal.go b/wal.go
index a923f5b3d..5962711f9 100644
--- a/wal.go
+++ b/wal.go
@@ -58,7 +58,7 @@ type WAL struct {
 
 const (
 	walDirName          = "wal"
-	walSegmentSizeBytes = 64 * 1000 * 1000 // 64 MB
+	walSegmentSizeBytes = 256 * 1024 * 1024 // 256 MB
 )
 
 // OpenWAL opens or creates a write ahead log in the given directory.