blob: c00b866680a2534900091979c2a7e3054d0b56a3 [file] [log] [blame]
// run
// Copyright 2009 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.
// Test heap sampling logic.
package main
import (
"fmt"
"math"
"runtime"
)
var a16 *[16]byte
var a512 *[512]byte
var a256 *[256]byte
var a1k *[1024]byte
var a64k *[64 * 1024]byte
// This test checks that heap sampling produces reasonable
// results. Note that heap sampling uses randomization, so the results
// vary for run to run. This test only checks that the resulting
// values appear reasonable.
func main() {
const countInterleaved = 10000
allocInterleaved(countInterleaved)
checkAllocations(getMemProfileRecords(), "main.allocInterleaved", countInterleaved, []int64{256 * 1024, 1024, 256 * 1024, 512, 256 * 1024, 256})
const count = 100000
alloc(count)
checkAllocations(getMemProfileRecords(), "main.alloc", count, []int64{1024, 512, 256})
}
// allocInterleaved stress-tests the heap sampling logic by
// interleaving large and small allocations.
func allocInterleaved(n int) {
for i := 0; i < n; i++ {
// Test verification depends on these lines being contiguous.
a64k = new([64 * 1024]byte)
a1k = new([1024]byte)
a64k = new([64 * 1024]byte)
a512 = new([512]byte)
a64k = new([64 * 1024]byte)
a256 = new([256]byte)
}
}
// alloc performs only small allocations for sanity testing.
func alloc(n int) {
for i := 0; i < n; i++ {
// Test verification depends on these lines being contiguous.
a1k = new([1024]byte)
a512 = new([512]byte)
a256 = new([256]byte)
}
}
// checkAllocations validates that the profile records collected for
// the named function are consistent with count contiguous allocations
// of the specified sizes.
func checkAllocations(records []runtime.MemProfileRecord, fname string, count int64, size []int64) {
a := allocObjects(records, fname)
firstLine := 0
for ln := range a {
if firstLine == 0 || firstLine > ln {
firstLine = ln
}
}
var totalcount int64
for i, w := range size {
ln := firstLine + i
s := a[ln]
checkValue(fname, ln, "objects", count, s.objects)
checkValue(fname, ln, "bytes", count*w, s.bytes)
totalcount += s.objects
}
// Check the total number of allocations, to ensure some sampling occurred.
if totalwant := count * int64(len(size)); totalcount <= 0 || totalcount > totalwant*1024 {
panic(fmt.Sprintf("%s want total count > 0 && <= %d, got %d", fname, totalwant*1024, totalcount))
}
}
// checkValue checks an unsampled value against a range.
func checkValue(fname string, ln int, name string, want, got int64) {
if got < 0 || got > 1024*want {
panic(fmt.Sprintf("%s:%d want %s >= 0 && <= %d, got %d", fname, ln, name, 1024*want, got))
}
}
func getMemProfileRecords() []runtime.MemProfileRecord {
// Force the runtime to update the object and byte counts.
// This can take up to two GC cycles to get a complete
// snapshot of the current point in time.
runtime.GC()
runtime.GC()
// Find out how many records there are (MemProfile(nil, true)),
// allocate that many records, and get the data.
// There's a race—more records might be added between
// the two calls—so allocate a few extra records for safety
// and also try again if we're very unlucky.
// The loop should only execute one iteration in the common case.
var p []runtime.MemProfileRecord
n, ok := runtime.MemProfile(nil, true)
for {
// Allocate room for a slightly bigger profile,
// in case a few more entries have been added
// since the call to MemProfile.
p = make([]runtime.MemProfileRecord, n+50)
n, ok = runtime.MemProfile(p, true)
if ok {
p = p[0:n]
break
}
// Profile grew; try again.
}
return p
}
type allocStat struct {
bytes, objects int64
}
// allocObjects examines the profile records for the named function
// and returns the allocation stats aggregated by source line number.
func allocObjects(records []runtime.MemProfileRecord, function string) map[int]allocStat {
a := make(map[int]allocStat)
for _, r := range records {
for _, s := range r.Stack0 {
if s == 0 {
break
}
if f := runtime.FuncForPC(s); f != nil {
name := f.Name()
_, line := f.FileLine(s)
if name == function {
allocStat := a[line]
allocStat.bytes += r.AllocBytes
allocStat.objects += r.AllocObjects
a[line] = allocStat
}
}
}
}
for line, stats := range a {
objects, bytes := scaleHeapSample(stats.objects, stats.bytes, int64(runtime.MemProfileRate))
a[line] = allocStat{bytes, objects}
}
return a
}
// scaleHeapSample unsamples heap allocations.
// Taken from src/cmd/pprof/internal/profile/legacy_profile.go
func scaleHeapSample(count, size, rate int64) (int64, int64) {
if count == 0 || size == 0 {
return 0, 0
}
if rate <= 1 {
// if rate==1 all samples were collected so no adjustment is needed.
// if rate<1 treat as unknown and skip scaling.
return count, size
}
avgSize := float64(size) / float64(count)
scale := 1 / (1 - math.Exp(-avgSize/float64(rate)))
return int64(float64(count) * scale), int64(float64(size) * scale)
}