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go/test/gc2.go
Russ Cox 507df959e4 runtime: drop chan circular linked list in favor of circular buffer
The list elements are already being allocated out of a
single memory buffer.  We can drop the Link* pointer
following and the memory it requires, replacing it with
index operations.

The change also keeps a channel from containing a pointer
back into its own allocation block, which would create a
cycle.  Blocks involved in cycles are not guaranteed to be
finalized properly, and channels depend on finalizers to
free OS-level locks on some systems.  The self-reference
was keeping channels from being garbage collected.

runtime-gdb.py will need to be updated in order to dump
the content of buffered channels with the new data structure.

Fixes #1676.

R=ken2, r
CC=golang-dev
https://golang.org/cl/4411045
2011-04-13 23:42:06 -04:00

42 lines
890 B
Go

// $G $D/$F.go && $L $F.$A && ./$A.out
// Copyright 2011 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.
// Check that buffered channels are garbage collected properly.
// An interesting case because they have finalizers and used to
// have self loops that kept them from being collected.
// (Cyclic data with finalizers is never finalized, nor collected.)
package main
import (
"fmt"
"os"
"runtime"
)
func main() {
const N = 10000
st := runtime.MemStats
for i := 0; i < N; i++ {
c := make(chan int, 10)
_ = c
if i%100 == 0 {
for j := 0; j < 4; j++ {
runtime.GC()
runtime.Gosched()
runtime.GC()
runtime.Gosched()
}
}
}
obj := runtime.MemStats.HeapObjects - st.HeapObjects
if obj > N/5 {
fmt.Println("too many objects left:", obj)
os.Exit(1)
}
}