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https://github.com/golang/go
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0011342590
This test erroneously assumes that there will always be at least one live object accounted for in a MemProfileRecord. This is not true; all memory allocated from a particular location could be dead. Fixes #64153. Change-Id: Iadb783ea9b247823439ddc74b62a4c8b2ce8e33e Reviewed-on: https://go-review.googlesource.com/c/go/+/542736 Reviewed-by: Cherry Mui <cherryyz@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
80 lines
2.1 KiB
Go
80 lines
2.1 KiB
Go
// run
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// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Test that tiny allocations with finalizers are correctly profiled.
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// Previously profile special records could have been processed prematurely
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// (while the object is still live).
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package main
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import (
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"runtime"
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"time"
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"unsafe"
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)
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func main() {
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runtime.MemProfileRate = 1
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// Allocate 1M 4-byte objects and set a finalizer for every third object.
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// Assuming that tiny block size is 16, some objects get finalizers setup
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// only for middle bytes. The finalizer resurrects that object.
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// As the result, all allocated memory must stay alive.
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const (
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N = 1 << 20
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tinyBlockSize = 16 // runtime._TinySize
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)
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hold := make([]*int32, 0, N)
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for i := 0; i < N; i++ {
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x := new(int32)
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if i%3 == 0 {
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runtime.SetFinalizer(x, func(p *int32) {
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hold = append(hold, p)
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})
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}
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}
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// Finalize as much as possible.
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// Note: the sleep only increases probability of bug detection,
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// it cannot lead to false failure.
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for i := 0; i < 5; i++ {
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runtime.GC()
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time.Sleep(10 * time.Millisecond)
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}
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// Read memory profile.
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var prof []runtime.MemProfileRecord
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for {
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if n, ok := runtime.MemProfile(prof, false); ok {
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prof = prof[:n]
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break
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} else {
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prof = make([]runtime.MemProfileRecord, n+10)
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}
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}
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// See how much memory in tiny objects is profiled.
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var totalBytes int64
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for _, p := range prof {
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bytes := p.AllocBytes - p.FreeBytes
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nobj := p.AllocObjects - p.FreeObjects
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if nobj == 0 {
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// There may be a record that has had all of its objects
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// freed. That's fine. Avoid a divide-by-zero and skip.
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continue
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}
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size := bytes / nobj
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if size == tinyBlockSize {
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totalBytes += bytes
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}
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}
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// 2*tinyBlockSize slack is for any boundary effects.
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if want := N*int64(unsafe.Sizeof(int32(0))) - 2*tinyBlockSize; totalBytes < want {
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println("got", totalBytes, "want >=", want)
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panic("some of the tiny objects are not profiled")
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}
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// Just to keep hold alive.
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if len(hold) != 0 && hold[0] == nil {
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panic("bad")
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}
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}
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