diff --git a/ants.go b/ants.go
index 7d6b161..5c2248f 100644
--- a/ants.go
+++ b/ants.go
@@ -10,10 +10,15 @@ func Push(task f) error {
 	return defaultPool.Push(task)
 }
 
-func Size() int {
-	return int(defaultPool.Running())
+func Running() int {
+	return defaultPool.Running()
 }
 
 func Cap() int {
-	return int(defaultPool.Cap())
+	return defaultPool.Cap()
 }
+
+func Free() int {
+	return defaultPool.Free()
+}
+
diff --git a/ants_benchmark_test.go b/ants_benchmark_test.go
new file mode 100644
index 0000000..d3306c4
--- /dev/null
+++ b/ants_benchmark_test.go
@@ -0,0 +1 @@
+package ants
diff --git a/ants_test.go b/ants_test.go
index 2e071ec..24afdb1 100644
--- a/ants_test.go
+++ b/ants_test.go
@@ -1,3 +1,53 @@
-package ants
+package ants_test
 
-import "testing"
+import (
+	"testing"
+	"github.com/panjf2000/ants"
+	"fmt"
+	"runtime"
+)
+
+var n = 100000
+
+func demoFunc() {
+	for i := 0; i < 1000000; i++ {}
+}
+
+func TestDefaultPool(t *testing.T) {
+	for i := 0; i < n; i++ {
+		ants.Push(demoFunc)
+	}
+
+	t.Logf("pool capacity:%d", ants.Cap())
+	t.Logf("running workers number:%d", ants.Running())
+	t.Logf("free workers number:%d", ants.Free())
+
+	mem := runtime.MemStats{}
+	runtime.ReadMemStats(&mem)
+	fmt.Println("memory usage:", mem.TotalAlloc/1024)
+}
+
+//func TestCustomPool(t *testing.T) {
+//	p := ants.NewPool(1000)
+//	for i := 0; i < n; i++ {
+//		p.Push(demoFunc)
+//	}
+//
+//	t.Logf("pool capacity:%d", p.Cap())
+//	t.Logf("running workers number:%d", p.Running())
+//	t.Logf("free workers number:%d", p.Free())
+//
+//	mem := runtime.MemStats{}
+//	runtime.ReadMemStats(&mem)
+//
+//}
+
+func TestNoPool(t *testing.T) {
+	for i := 0; i < n; i++ {
+		go demoFunc()
+	}
+	mem := runtime.MemStats{}
+	runtime.ReadMemStats(&mem)
+	fmt.Println("memory usage:", mem.TotalAlloc/1024)
+
+}
diff --git a/pool.go b/pool.go
index 2f5fa26..45bf9f3 100644
--- a/pool.go
+++ b/pool.go
@@ -56,16 +56,16 @@ func (p *Pool) Push(task f) error {
 	p.tasks <- task
 	return nil
 }
-func (p *Pool) Running() int32 {
-	return atomic.LoadInt32(&p.running)
+func (p *Pool) Running() int {
+	return int(atomic.LoadInt32(&p.running))
 }
 
-func (p *Pool) Free() int32 {
-	return atomic.LoadInt32(&p.capacity) - atomic.LoadInt32(&p.running)
+func (p *Pool) Free() int {
+	return int(atomic.LoadInt32(&p.capacity) - atomic.LoadInt32(&p.running))
 }
 
-func (p *Pool) Cap() int32 {
-	return atomic.LoadInt32(&p.capacity)
+func (p *Pool) Cap() int {
+	return int(atomic.LoadInt32(&p.capacity))
 }
 
 func (p *Pool) Destroy() error {
@@ -90,11 +90,11 @@ func (p *Pool) newWorker() *Worker {
 		exit: make(chan sig),
 	}
 	worker.run()
-	atomic.AddInt32(&p.running, 1)
 	return worker
 }
 
 func (p *Pool) getWorker() *Worker {
+	defer atomic.AddInt32(&p.running, 1)
 	var worker *Worker
 	if p.reachLimit() {
 		worker = <-p.workers