// Copyright 2017 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
// +build 386 amd64
package runtime_test
import (
"testing"
"time"
_ "unsafe"
)
// These tests are a little risky because they overwrite the __vdso_clock_gettime_sym value.
// It's normally initialized at startup and remains unchanged after that.
//go:linkname __vdso_clock_gettime_sym runtime.__vdso_clock_gettime_sym
var __vdso_clock_gettime_sym uintptr
func TestClockVDSOAndFallbackPaths(t *testing.T) {
// Check that we can call walltime() and nanotime() with and without their (1st) fast-paths.
// This just checks that fast and fallback paths can be called, rather than testing their
// results.
//
// Call them indirectly via time.Now(), so we don't need auxiliary .s files to allow us to
// use go:linkname to refer to the functions directly.
save := __vdso_clock_gettime_sym
if save == 0 {
t.Log("__vdso_clock_gettime symbol not found; fallback path will be used by default")
}
// Call with fast-path enabled (if vDSO symbol found at startup)
time.Now()
// Call with fast-path disabled
__vdso_clock_gettime_sym = 0
time.Now()
__vdso_clock_gettime_sym = save
}
func BenchmarkClockVDSOAndFallbackPaths(b *testing.B) {
run := func(b *testing.B) {
for i := 0; i < b.N; i++ {
// Call via time.Now() - see comment in test above.
time.Now()
}
}
save := __vdso_clock_gettime_sym
b.Run("vDSO", run)
__vdso_clock_gettime_sym = 0
b.Run("Fallback", run)
__vdso_clock_gettime_sym = save
}
func BenchmarkTimeNow(b *testing.B) {
for i := 0; i < b.N; i++ {
time.Now()
}
}