net/url: improve URL.String performance
URL.String performs memory allocation many times, but it can improve
performance by allocating memory that it clearly knows it needs.
This CL achieves 24.6% speedup, 18.3% memory reduction, and 46.7% fewer memory
allocations on existing benchmarks.
│ string_old.txt │ string_new2.txt │
│ sec/op │ sec/op vs base │
String-16 3.622µ ± 5% 2.730µ ± 2% -24.63% (p=0.000 n=10)
│ string_old.txt │ string_new2.txt │
│ B/op │ B/op vs base │
String-16 1.406Ki ± 0% 1.148Ki ± 0% -18.33% (p=0.000 n=10)
│ string_old.txt │ string_new2.txt │
│ allocs/op │ allocs/op vs base │
String-16 60.00 ± 0% 32.00 ± 0% -46.67% (p=0.000 n=10)
Change-Id: I70199be952eddc44134945077e52740e8921088f
Reviewed-on: https://go-review.googlesource.com/c/go/+/581155
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
Reviewed-by: Joedian Reid <joedian@google.com>
diff --git a/src/net/url/url.go b/src/net/url/url.go
index f362958..7cd6913 100644
--- a/src/net/url/url.go
+++ b/src/net/url/url.go
@@ -814,6 +814,22 @@
// - if u.Fragment is empty, #fragment is omitted.
func (u *URL) String() string {
var buf strings.Builder
+
+ n := len(u.Scheme)
+ if u.Opaque != "" {
+ n += len(u.Opaque)
+ } else {
+ if !u.OmitHost && (u.Scheme != "" || u.Host != "" || u.User != nil) {
+ username := u.User.Username()
+ password, _ := u.User.Password()
+ n += len(username) + len(password) + len(u.Host)
+ }
+ n += len(u.Path)
+ }
+ n += len(u.RawQuery) + len(u.RawFragment)
+ n += len(":" + "//" + "//" + ":" + "@" + "/" + "./" + "?" + "#")
+ buf.Grow(n)
+
if u.Scheme != "" {
buf.WriteString(u.Scheme)
buf.WriteByte(':')
