go/src/sync/pool_test.go

// Copyright 2013 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.

// Pool is no-op under race detector, so all these tests do not work.
// +build !race

package sync_test

import (
	"runtime"
	"runtime/debug"
	. "sync"
	"sync/atomic"
	"testing"
	"time"
)

func TestPool(t *testing.T) {
	// disable GC so we can control when it happens.
	defer debug.SetGCPercent(debug.SetGCPercent(-1))
	var p Pool
	if p.Get() != nil {
		t.Fatal("expected empty")
	}
	p.Put("a")
	p.Put("b")
	if g := p.Get(); g != "a" {
		t.Fatalf("got %#v; want a", g)
	}
	if g := p.Get(); g != "b" {
		t.Fatalf("got %#v; want b", g)
	}
	if g := p.Get(); g != nil {
		t.Fatalf("got %#v; want nil", g)
	}

	p.Put("c")
	debug.SetGCPercent(100) // to allow following GC to actually run
	runtime.GC()
	if g := p.Get(); g != nil {
		t.Fatalf("got %#v; want nil after GC", g)
	}
}

func TestPoolNew(t *testing.T) {
	// disable GC so we can control when it happens.
	defer debug.SetGCPercent(debug.SetGCPercent(-1))

	i := 0
	p := Pool{
		New: func() interface{} {
			i++
			return i
		},
	}
	if v := p.Get(); v != 1 {
		t.Fatalf("got %v; want 1", v)
	}
	if v := p.Get(); v != 2 {
		t.Fatalf("got %v; want 2", v)
	}
	p.Put(42)
	if v := p.Get(); v != 42 {
		t.Fatalf("got %v; want 42", v)
	}
	if v := p.Get(); v != 3 {
		t.Fatalf("got %v; want 3", v)
	}
}

// Test that Pool does not hold pointers to previously cached resources.
func TestPoolGC(t *testing.T) {
	testPool(t, true)
}

// Test that Pool releases resources on GC.
func TestPoolRelease(t *testing.T) {
	testPool(t, false)
}

func testPool(t *testing.T, drain bool) {
	var p Pool
	const N = 100
loop:
	for try := 0; try < 3; try++ {
		var fin, fin1 uint32
		for i := 0; i < N; i++ {
			v := new(string)
			runtime.SetFinalizer(v, func(vv *string) {
				atomic.AddUint32(&fin, 1)
			})
			p.Put(v)
		}
		if drain {
			for i := 0; i < N; i++ {
				p.Get()
			}
		}
		for i := 0; i < 5; i++ {
			runtime.GC()
			time.Sleep(time.Duration(i*100+10) * time.Millisecond)
			// 1 pointer can remain on stack or elsewhere
			if fin1 = atomic.LoadUint32(&fin); fin1 >= N-1 {
				continue loop
			}
		}
		t.Fatalf("only %v out of %v resources are finalized on try %v", fin1, N, try)
	}
}

func TestPoolStress(t *testing.T) {
	const P = 10
	N := int(1e6)
	if testing.Short() {
		N /= 100
	}
	var p Pool
	done := make(chan bool)
	for i := 0; i < P; i++ {
		go func() {
			var v interface{} = 0
			for j := 0; j < N; j++ {
				if v == nil {
					v = 0
				}
				p.Put(v)
				v = p.Get()
				if v != nil && v.(int) != 0 {
					t.Fatalf("expect 0, got %v", v)
				}
			}
			done <- true
		}()
	}
	for i := 0; i < P; i++ {
		<-done
	}
}

func BenchmarkPool(b *testing.B) {
	var p Pool
	b.RunParallel(func(pb *testing.PB) {
		for pb.Next() {
			p.Put(1)
			p.Get()
		}
	})
}

func BenchmarkPoolOverflow(b *testing.B) {
	var p Pool
	b.RunParallel(func(pb *testing.PB) {
		for pb.Next() {
			for b := 0; b < 100; b++ {
				p.Put(1)
			}
			for b := 0; b < 100; b++ {
				p.Get()
			}
		}
	})
}