sync: improve Pool performance

valyala · ianlancetaylor · commit af5c95117b26 · 2017-04-18T14:17:48.000Z
Rewrite indexLocal to achieve higher performance. Performance results on linux/amd64: name old time/op new time/op delta Pool-4 19.1ns ± 2% 10.1ns ± 1% -47.15% (p=0.000 n=10+8) PoolOverflow-4 3.11µs ± 1% 2.10µs ± 2% -32.66% (p=0.000 n=10+10) Performance results on linux/386: name old time/op new time/op delta Pool-4 20.0ns ± 2% 13.1ns ± 1% -34.59% (p=0.000 n=10+9) PoolOverflow-4 3.51µs ± 1% 2.49µs ± 0% -28.99% (p=0.000 n=10+8) Change-Id: I7d57a2d4cd47ec43d09ca1267bde2e3f05a9faa9 Reviewed-on: https://go-review.googlesource.com/40913 Reviewed-by: Ian Lance Taylor <iant@golang.org> Run-TryBot: Ian Lance Taylor <iant@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/sync/pool.go b/src/sync/pool.go
@@ -241,7 +241,8 @@ func init() {
 }
 
 func indexLocal(l unsafe.Pointer, i int) *poolLocal {
-	return &(*[1000000]poolLocal)(l)[i]
+	lp := unsafe.Pointer(uintptr(l) + uintptr(i)*unsafe.Sizeof(poolLocal{}))
+	return (*poolLocal)(lp)
 }
 
 // Implemented in runtime.

Original file line number	Diff line number	Diff line change
`@@ -241,7 +241,8 @@ func init() {`
`241`	`241`	`}`
`242`	`242`
`243`	`243`	`func indexLocal(l unsafe.Pointer, i int) *poolLocal {`
`244`		`- return &(*[1000000]poolLocal)(l)[i]`
	`244`	`+ lp := unsafe.Pointer(uintptr(l) + uintptr(i)*unsafe.Sizeof(poolLocal{}))`
	`245`	`+ return (*poolLocal)(lp)`
`245`	`246`	`}`
`246`	`247`
`247`	`248`	`// Implemented in runtime.`