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// run
//go:build amd64
// Copyright 2016 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 "runtime"
type big [10 << 20]byte
func f(x *big, start int64) {
if delta := inuse() - start; delta < 9<<20 {
println("after alloc: expected delta at least 9MB, got: ", delta)
}
runtime.KeepAlive(x)
x = nil
if delta := inuse() - start; delta > 1<<20 {
println("after drop: expected delta below 1MB, got: ", delta)
}
x = new(big)
if delta := inuse() - start; delta < 9<<20 {
println("second alloc: expected delta at least 9MB, got: ", delta)
}
runtime.KeepAlive(x)
}
func main() {
x := inuse()
f(new(big), x)
}
func inuse() int64 {
runtime.GC()
var st runtime.MemStats
runtime.ReadMemStats(&st)
return int64(st.Alloc)
}
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