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// run
// Copyright 2015 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 that tiny allocations with finalizers are correctly profiled.
// Previously profile special records could have been processed prematurely
// (while the object is still live).
package main
import (
"runtime"
"time"
"unsafe"
)
func main() {
runtime.MemProfileRate = 1
// Allocate 1M 4-byte objects and set a finalizer for every third object.
// Assuming that tiny block size is 16, some objects get finalizers setup
// only for middle bytes. The finalizer resurrects that object.
// As the result, all allocated memory must stay alive.
const (
N = 1 << 20
tinyBlockSize = 16 // runtime._TinySize
)
hold := make([]*int32, 0, N)
for i := 0; i < N; i++ {
x := new(int32)
if i%3 == 0 {
runtime.SetFinalizer(x, func(p *int32) {
hold = append(hold, p)
})
}
}
// Finalize as much as possible.
// Note: the sleep only increases probability of bug detection,
// it cannot lead to false failure.
for i := 0; i < 5; i++ {
runtime.GC()
time.Sleep(10 * time.Millisecond)
}
// Read memory profile.
var prof []runtime.MemProfileRecord
for {
if n, ok := runtime.MemProfile(prof, false); ok {
prof = prof[:n]
break
} else {
prof = make([]runtime.MemProfileRecord, n+10)
}
}
// See how much memory in tiny objects is profiled.
var totalBytes int64
for _, p := range prof {
bytes := p.AllocBytes - p.FreeBytes
nobj := p.AllocObjects - p.FreeObjects
if nobj == 0 {
// There may be a record that has had all of its objects
// freed. That's fine. Avoid a divide-by-zero and skip.
continue
}
size := bytes / nobj
if size == tinyBlockSize {
totalBytes += bytes
}
}
// 2*tinyBlockSize slack is for any boundary effects.
if want := N*int64(unsafe.Sizeof(int32(0))) - 2*tinyBlockSize; totalBytes < want {
println("got", totalBytes, "want >=", want)
panic("some of the tiny objects are not profiled")
}
// Just to keep hold alive.
if len(hold) != 0 && hold[0] == nil {
panic("bad")
}
}
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