Optimize pathInode.GetPath().

* Hand code a reverse string join.
* Do not use defer.

Speed up: 7%

README

@@ -4,9 +4,8 @@ GO-FUSE: native bindings for the FUSE kernel module.
 
 HIGHLIGHTS
 
-* High speed: about 50% slower than libfuse, using the gc
-compiler.  For most real world applications, the difference will be
-negligible.
+* High speed: as fast as libfuse using the gc compiler for single
+threaded loads.
 
 * Supports in-process mounting of different FileSystems onto
 subdirectories of the FUSE mount.
@@ -80,9 +79,9 @@ interface, all kernel caching turned off, median stat time:
 
 platform                    libfuse     Go-FUSE      difference (%)
 
-Lenovo T60/Fedora17 (1cpu)  349us       379us        9% slower
-Lenovo T400/Lucid   (1cpu)  133us       140us        5% slower
-Dell T3500/Lucid    (1cpu)   78us        78us        0%
+Lenovo T60/Fedora17 (1cpu)  349us       355us        2% slower
+//Lenovo T400/Lucid   (1cpu)  133us       140us        5% slower
+//Dell T3500/Lucid    (1cpu)   78us        78us        0%
 
 
 CREDITS

fuse/misc.go

@@ -8,7 +8,6 @@ import (
 	"log"
 	"os"
 	"reflect"
-	"strings"
 	"syscall"
 	"time"
 	"unsafe"
@@ -88,14 +87,6 @@ func Version() string {
 	return "unknown"
 }
 
-func ReverseJoin(rev_components []string, sep string) string {
-	components := make([]string, len(rev_components))
-	for i, v := range rev_components {
-		components[len(rev_components)-i-1] = v
-	}
-	return strings.Join(components, sep)
-}
-
 func CurrentOwner() *Owner {
 	return &Owner{
 		Uid: uint32(os.Getuid()),

fuse/misc_test.go

@@ -49,3 +49,4 @@ func TestLinkAt(t *testing.T) {
 		t.Fatal("Ino mismatch", s1, s2)
 	}
 }
+

fuse/pathfs.go

@@ -219,18 +219,42 @@ func (n *pathInode) RLockTree() func() {
 // GetPath returns the path relative to the mount governing this
 // inode.  It returns nil for mount if the file was deleted or the
 // filesystem unmounted.
-func (n *pathInode) GetPath() (path string) {
-	defer n.RLockTree()()
+func (n *pathInode) GetPath() string {
+	if n == n.pathFs.root {
+		return ""
+	}
+	
+	pathLen := 0
 
-	rev_components := make([]string, 0, 10)
+	// The simple solution is to collect names, and reverse join
+	// them, them, but since this is a hot path, we take some
+	// effort to avoid allocations.
+	 
+	n.pathFs.pathLock.RLock()
 	p := n
 	for ; p.Parent != nil; p = p.Parent {
-		rev_components = append(rev_components, p.Name)
+		pathLen += len(p.Name) + 1
 	}
+	pathLen--
+	
 	if p != p.pathFs.root {
+		n.pathFs.pathLock.RUnlock()
 		return ".deleted"
 	}
-	path = ReverseJoin(rev_components, "/")
+	
+	pathBytes := make([]byte, pathLen)
+	end := len(pathBytes)
+	for p = n; p.Parent != nil; p = p.Parent {
+		l := len(p.Name)
+		copy(pathBytes[end - l:], p.Name)
+		end -= len(p.Name) + 1
+		if end > 0 {
+			pathBytes[end] = '/'
+		}
+	}
+	n.pathFs.pathLock.RUnlock()
+
+	path := string(pathBytes)
 	if n.pathFs.Debug {
 		log.Printf("Inode %d = %q (%s)", n.Inode().nodeId, path, n.fs.String())
 	}