1
2
3
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
94 gcstats("BenchmarkTree2", N, time.Now().Sub(t0))
95 }
96
View as plain text