// Copyright 2017 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build linux
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// +build 386 amd64 arm arm64 ppc64 ppc64le
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package runtime_test
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import (
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"testing"
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"time"
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_ "unsafe"
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)
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// These tests are a little risky because they overwrite the vdsoClockgettimeSym value.
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// It's normally initialized at startup and remains unchanged after that.
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//go:linkname vdsoClockgettimeSym runtime.vdsoClockgettimeSym
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var vdsoClockgettimeSym uintptr
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func TestClockVDSOAndFallbackPaths(t *testing.T) {
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// Check that we can call walltime() and nanotime() with and without their (1st) fast-paths.
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// This just checks that fast and fallback paths can be called, rather than testing their
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// results.
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//
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// Call them indirectly via time.Now(), so we don't need auxiliary .s files to allow us to
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// use go:linkname to refer to the functions directly.
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save := vdsoClockgettimeSym
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if save == 0 {
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t.Log("vdsoClockgettime symbol not found; fallback path will be used by default")
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}
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// Call with fast-path enabled (if vDSO symbol found at startup)
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time.Now()
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// Call with fast-path disabled
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vdsoClockgettimeSym = 0
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time.Now()
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vdsoClockgettimeSym = save
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}
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func BenchmarkClockVDSOAndFallbackPaths(b *testing.B) {
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run := func(b *testing.B) {
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for i := 0; i < b.N; i++ {
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// Call via time.Now() - see comment in test above.
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time.Now()
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}
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}
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save := vdsoClockgettimeSym
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b.Run("vDSO", run)
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vdsoClockgettimeSym = 0
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b.Run("Fallback", run)
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vdsoClockgettimeSym = save
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}
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func BenchmarkTimeNow(b *testing.B) {
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for i := 0; i < b.N; i++ {
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time.Now()
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}
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}
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