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// Copyright 2012 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.
package main
import (
"flag"
"fmt"
"log"
"os"
"runtime"
"runtime/pprof"
"unsafe"
)
const BranchingFactor = 4
type Object struct {
child [BranchingFactor]*Object
}
var (
cpus = flag.Int("cpus", 1, "number of cpus to use")
heapsize = flag.Int64("heapsize", 100*1024*1024, "size of the heap in bytes")
cpuprofile = flag.String("cpuprofile", "", "write cpu profile to file")
lastPauseNs uint64 = 0
lastFree uint64 = 0
heap *Object
calls [20]int
numobjects int64
memstats runtime.MemStats
)
func buildHeap() {
objsize := int64(unsafe.Sizeof(Object{}))
heap, _ = buildTree(float64(objsize), float64(*heapsize), 0)
fmt.Printf("*** built heap: %.0f MB; (%d objects * %d bytes)\n",
float64(*heapsize)/1048576, numobjects, objsize)
}
func buildTree(objsize, size float64, depth int) (*Object, float64) {
calls[depth]++
x := &Object{}
numobjects++
subtreeSize := (size - objsize) / BranchingFactor
alloc := objsize
for i := 0; i < BranchingFactor && alloc < size; i++ {
c, n := buildTree(objsize, subtreeSize, depth+1)
x.child[i] = c
alloc += n
}
return x, alloc
}
func gc() {
runtime.GC()
runtime.ReadMemStats(&memstats)
pause := memstats.PauseTotalNs
inuse := memstats.Alloc
free := memstats.TotalAlloc - inuse
fmt.Printf("gc pause: %8.3f ms; collect: %8.0f MB; heapsize: %8.0f MB\n",
float64(pause-lastPauseNs)/1e6,
float64(free-lastFree)/1048576,
float64(inuse)/1048576)
lastPauseNs = pause
lastFree = free
}
func main() {
flag.Parse()
buildHeap()
runtime.GOMAXPROCS(*cpus)
runtime.ReadMemStats(&memstats)
lastPauseNs = memstats.PauseTotalNs
lastFree = memstats.TotalAlloc - memstats.Alloc
if *cpuprofile != "" {
f, err := os.Create(*cpuprofile)
if err != nil {
log.Fatal(err)
}
pprof.StartCPUProfile(f)
defer pprof.StopCPUProfile()
}
for i := 0; i < 10; i++ {
gc()
}
}
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