1 // Copyright 2012 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 package main 6 7 import ( 8 "flag" 9 "fmt" 10 "log" 11 "os" 12 "runtime" 13 "runtime/pprof" 14 "time" 15 "unsafe" 16 ) 17 18 const BranchingFactor = 4 19 20 type Object struct { 21 child [BranchingFactor]*Object 22 } 23 24 var ( 25 cpus = flag.Int("cpus", 1, "number of cpus to use") 26 heapsize = flag.Int64("heapsize", 100*1024*1024, "size of the heap in bytes") 27 cpuprofile = flag.String("cpuprofile", "", "write cpu profile to file") 28 29 lastPauseNs uint64 = 0 30 lastFree uint64 = 0 31 heap *Object 32 calls [20]int 33 numobjects int64 34 memstats runtime.MemStats 35 ) 36 37 func buildHeap() { 38 objsize := int64(unsafe.Sizeof(Object{})) 39 heap, _ = buildTree(float64(objsize), float64(*heapsize), 0) 40 fmt.Printf("*** built heap: %.0f MB; (%d objects * %d bytes)\n", 41 float64(*heapsize)/1048576, numobjects, objsize) 42 } 43 44 func buildTree(objsize, size float64, depth int) (*Object, float64) { 45 calls[depth]++ 46 x := &Object{} 47 numobjects++ 48 subtreeSize := (size - objsize) / BranchingFactor 49 alloc := objsize 50 for i := 0; i < BranchingFactor && alloc < size; i++ { 51 c, n := buildTree(objsize, subtreeSize, depth+1) 52 x.child[i] = c 53 alloc += n 54 } 55 return x, alloc 56 } 57 58 func gc() { 59 runtime.GC() 60 runtime.ReadMemStats(&memstats) 61 pause := memstats.PauseTotalNs 62 inuse := memstats.Alloc 63 free := memstats.TotalAlloc - inuse 64 fmt.Printf("gc pause: %8.3f ms; collect: %8.0f MB; heapsize: %8.0f MB\n", 65 float64(pause-lastPauseNs)/1e6, 66 float64(free-lastFree)/1048576, 67 float64(inuse)/1048576) 68 lastPauseNs = pause 69 lastFree = free 70 } 71 72 func main() { 73 flag.Parse() 74 buildHeap() 75 runtime.GOMAXPROCS(*cpus) 76 runtime.ReadMemStats(&memstats) 77 lastPauseNs = memstats.PauseTotalNs 78 lastFree = memstats.TotalAlloc - memstats.Alloc 79 if *cpuprofile != "" { 80 f, err := os.Create(*cpuprofile) 81 if err != nil { 82 log.Fatal(err) 83 } 84 pprof.StartCPUProfile(f) 85 defer pprof.StopCPUProfile() 86 } 87 const N = 10 88 var t0 time.Time 89 for i := 0; i < N; i++ { 90 t0 = time.Now() 91 gc() 92 } 93 // Standard gotest benchmark output, collected by build dashboard. 94 gcstats("BenchmarkTree2", N, time.Now().Sub(t0)) 95 } 96
