runtime: Implement faster equals for strings and bytes.
(amd64)
benchmark old ns/op new ns/op delta
BenchmarkEqual0 16 6 -63.15%
BenchmarkEqual9 22 7 -65.37%
BenchmarkEqual32 36 9 -74.91%
BenchmarkEqual4K 2187 120 -94.51%
benchmark old MB/s new MB/s speedup
BenchmarkEqual9 392.22 1134.38 2.89x
BenchmarkEqual32 866.72 3457.39 3.99x
BenchmarkEqual4K 1872.73 33998.87 18.15x
(386)
benchmark old ns/op new ns/op delta
BenchmarkEqual0 16 5 -63.85%
BenchmarkEqual9 22 7 -67.84%
BenchmarkEqual32 34 12 -64.94%
BenchmarkEqual4K 2196 113 -94.85%
benchmark old MB/s new MB/s speedup
BenchmarkEqual9 405.81 1260.18 3.11x
BenchmarkEqual32 919.55 2631.21 2.86x
BenchmarkEqual4K 1864.85 36072.54 19.34x
Update #3751
R=bradfitz, r, khr, dave, remyoudompheng, fullung, minux.ma, ality
CC=golang-dev
https://golang.org/cl/8056043
diff --git a/src/pkg/bytes/equal_test.go b/src/pkg/bytes/equal_test.go
new file mode 100644
index 0000000..a393d5e
--- /dev/null
+++ b/src/pkg/bytes/equal_test.go
@@ -0,0 +1,45 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+//
+// +build linux
+
+package bytes_test
+
+import (
+ . "bytes"
+ "syscall"
+ "testing"
+ "unsafe"
+)
+
+// This file tests the situation where memeq is checking
+// data very near to a page boundary. We want to make sure
+// equal does not read across the boundary and cause a page
+// fault where it shouldn't.
+
+// This test runs only on linux. The code being tested is
+// not OS-specific, so it does not need to be tested on all
+// operating systems.
+
+func TestEqualNearPageBoundary(t *testing.T) {
+ pagesize := syscall.Getpagesize()
+ b := make([]byte, 4*pagesize)
+ i := pagesize
+ for ; uintptr(unsafe.Pointer(&b[i]))%uintptr(pagesize) != 0; i++ {
+ }
+ syscall.Mprotect(b[i-pagesize:i], 0)
+ syscall.Mprotect(b[i+pagesize:i+2*pagesize], 0)
+
+ // both of these should fault
+ //pagesize += int(b[i-1])
+ //pagesize += int(b[i+pagesize])
+
+ for j := 0; j < pagesize; j++ {
+ b[i+j] = 'A'
+ }
+ for j := 0; j <= pagesize; j++ {
+ Equal(b[i:i+j], b[i+pagesize-j:i+pagesize])
+ Equal(b[i+pagesize-j:i+pagesize], b[i:i+j])
+ }
+}
