1 // Copyright 2017 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // +build linux 6 // +build 386 amd64 7 8 package runtime_test 9 10 import ( 11 "testing" 12 "time" 13 _ "unsafe" 14 ) 15 16 // These tests are a little risky because they overwrite the __vdso_clock_gettime_sym value. 17 // It's normally initialized at startup and remains unchanged after that. 18 19 //go:linkname __vdso_clock_gettime_sym runtime.__vdso_clock_gettime_sym 20 var __vdso_clock_gettime_sym uintptr 21 22 func TestClockVDSOAndFallbackPaths(t *testing.T) { 23 // Check that we can call walltime() and nanotime() with and without their (1st) fast-paths. 24 // This just checks that fast and fallback paths can be called, rather than testing their 25 // results. 26 // 27 // Call them indirectly via time.Now(), so we don't need auxiliary .s files to allow us to 28 // use go:linkname to refer to the functions directly. 29 30 save := __vdso_clock_gettime_sym 31 if save == 0 { 32 t.Log("__vdso_clock_gettime symbol not found; fallback path will be used by default") 33 } 34 35 // Call with fast-path enabled (if vDSO symbol found at startup) 36 time.Now() 37 38 // Call with fast-path disabled 39 __vdso_clock_gettime_sym = 0 40 time.Now() 41 __vdso_clock_gettime_sym = save 42 } 43 44 func BenchmarkClockVDSOAndFallbackPaths(b *testing.B) { 45 run := func(b *testing.B) { 46 for i := 0; i < b.N; i++ { 47 // Call via time.Now() - see comment in test above. 48 time.Now() 49 } 50 } 51 52 save := __vdso_clock_gettime_sym 53 b.Run("vDSO", run) 54 __vdso_clock_gettime_sym = 0 55 b.Run("Fallback", run) 56 __vdso_clock_gettime_sym = save 57 } 58 59 func BenchmarkTimeNow(b *testing.B) { 60 for i := 0; i < b.N; i++ { 61 time.Now() 62 } 63 } 64
