Merge pull request #1888 from stevvooe/more-efficient-path-comparison

registry/storage: more efficient path compare in catalog
This commit is contained in:
Richard Scothern 2016-08-09 13:45:07 -07:00 committed by GitHub
commit 9000745401
2 changed files with 127 additions and 15 deletions

View file

@ -38,7 +38,7 @@ func (reg *registry) Repositories(ctx context.Context, repos []string, last stri
_, file := path.Split(repoPath) _, file := path.Split(repoPath)
if file == "_layers" { if file == "_layers" {
repoPath = strings.TrimSuffix(repoPath, "/_layers") repoPath = strings.TrimSuffix(repoPath, "/_layers")
if pathGreaterThan(repoPath, last) { if lessPath(last, repoPath) {
foundRepos = append(foundRepos, repoPath) foundRepos = append(foundRepos, repoPath)
} }
return ErrSkipDir return ErrSkipDir
@ -100,22 +100,53 @@ func (reg *registry) Enumerate(ctx context.Context, ingester func(string) error)
} }
func pathGreaterThan(pathX, pathY string) (b bool) { // lessPath returns true if one path a is less than path b.
splitPathX := strings.SplitN(pathX, "/", 2) //
splitPathY := strings.SplitN(pathY, "/", 2) // A component-wise comparison is done, rather than the lexical comparison of
// strings.
func lessPath(a, b string) bool {
// we provide this behavior by making separator always sort first.
return compareReplaceInline(a, b, '/', '\x00') < 0
}
if splitPathX[0] == splitPathY[0] { // compareReplaceInline modifies runtime.cmpstring to replace old with new
if len(splitPathX) == 1 && len(splitPathY) == 1 { // during a byte-wise comparison.
return false func compareReplaceInline(s1, s2 string, old, new byte) int {
} else if len(splitPathX) == 1 && len(splitPathY) != 1 { // TODO(stevvooe): We are missing an optimization when the s1 and s2 have
return false // the exact same slice header. It will make the code unsafe but can
} else if len(splitPathX) != 1 && len(splitPathY) == 1 { // provide some extra performance.
return true
}
return pathGreaterThan(splitPathX[1], splitPathY[1])
l := len(s1)
if len(s2) < l {
l = len(s2)
} }
return splitPathX[0] > splitPathY[0] for i := 0; i < l; i++ {
c1, c2 := s1[i], s2[i]
if c1 == old {
c1 = new
}
if c2 == old {
c2 = new
}
if c1 < c2 {
return -1
}
if c1 > c2 {
return +1
}
}
if len(s1) < len(s2) {
return -1
}
if len(s1) > len(s2) {
return +1
}
return 0
} }

View file

@ -3,6 +3,7 @@ package storage
import ( import (
"fmt" "fmt"
"io" "io"
"math/rand"
"testing" "testing"
"github.com/docker/distribution" "github.com/docker/distribution"
@ -220,3 +221,83 @@ func TestCatalogWalkError(t *testing.T) {
t.Errorf("Expected catalog driver list error") t.Errorf("Expected catalog driver list error")
} }
} }
func BenchmarkPathCompareEqual(B *testing.B) {
B.StopTimer()
pp := randomPath(100)
// make a real copy
ppb := append([]byte{}, []byte(pp)...)
a, b := pp, string(ppb)
B.StartTimer()
for i := 0; i < B.N; i++ {
lessPath(a, b)
}
}
func BenchmarkPathCompareNotEqual(B *testing.B) {
B.StopTimer()
a, b := randomPath(100), randomPath(100)
B.StartTimer()
for i := 0; i < B.N; i++ {
lessPath(a, b)
}
}
func BenchmarkPathCompareNative(B *testing.B) {
B.StopTimer()
a, b := randomPath(100), randomPath(100)
B.StartTimer()
for i := 0; i < B.N; i++ {
c := a < b
c = c && false
}
}
func BenchmarkPathCompareNativeEqual(B *testing.B) {
B.StopTimer()
pp := randomPath(100)
a, b := pp, pp
B.StartTimer()
for i := 0; i < B.N; i++ {
c := a < b
c = c && false
}
}
var filenameChars = []byte("abcdefghijklmnopqrstuvwxyz0123456789")
var separatorChars = []byte("._-")
func randomPath(length int64) string {
path := "/"
for int64(len(path)) < length {
chunkLength := rand.Int63n(length-int64(len(path))) + 1
chunk := randomFilename(chunkLength)
path += chunk
remaining := length - int64(len(path))
if remaining == 1 {
path += randomFilename(1)
} else if remaining > 1 {
path += "/"
}
}
return path
}
func randomFilename(length int64) string {
b := make([]byte, length)
wasSeparator := true
for i := range b {
if !wasSeparator && i < len(b)-1 && rand.Intn(4) == 0 {
b[i] = separatorChars[rand.Intn(len(separatorChars))]
wasSeparator = true
} else {
b[i] = filenameChars[rand.Intn(len(filenameChars))]
wasSeparator = false
}
}
return string(b)
}