diff --git a/internal/caches/max_open_files.go b/internal/caches/max_open_files.go
index dfcb30b..c911230 100644
--- a/internal/caches/max_open_files.go
+++ b/internal/caches/max_open_files.go
@@ -3,44 +3,24 @@
 package caches
 
 import (
-	teaconst "github.com/TeaOSLab/EdgeNode/internal/const"
 	"github.com/TeaOSLab/EdgeNode/internal/goman"
 	"sync/atomic"
 	"time"
 )
 
 const (
-	minOpenFilesValue int32 = 4
-	maxOpenFilesValue int32 = 65535
-
 	modeSlow int32 = 1
 	modeFast int32 = 2
 )
 
 // MaxOpenFiles max open files manager
 type MaxOpenFiles struct {
-	step         int32
-	maxOpenFiles int32
-	ptr          *int32
-	ticker       *time.Ticker
-	mode         int32
-
-	lastOpens    int32
-	currentOpens int32
+	ticker *time.Ticker
+	mode   int32
 }
 
-func NewMaxOpenFiles(step int32) *MaxOpenFiles {
-	if step <= 0 {
-		step = 2
-	}
-	var f = &MaxOpenFiles{
-		step:         step,
-		maxOpenFiles: minOpenFilesValue,
-	}
-	if teaconst.DiskIsFast {
-		f.maxOpenFiles = 32
-	}
-	f.ptr = &f.maxOpenFiles
+func NewMaxOpenFiles() *MaxOpenFiles {
+	var f = &MaxOpenFiles{}
 	f.ticker = time.NewTicker(1 * time.Second)
 	f.init()
 	return f
@@ -49,50 +29,24 @@ func NewMaxOpenFiles(step int32) *MaxOpenFiles {
 func (this *MaxOpenFiles) init() {
 	goman.New(func() {
 		for range this.ticker.C {
-			var mod = atomic.LoadInt32(&this.mode)
-			switch mod {
-			case modeSlow:
-				// we decrease more quickly, with more steps
-				if atomic.AddInt32(this.ptr, -this.step*2) <= 0 {
-					atomic.StoreInt32(this.ptr, minOpenFilesValue)
-				}
-			case modeFast:
-				// we increase only when file opens increases
-				var currentOpens = atomic.LoadInt32(&this.currentOpens)
-				if currentOpens > this.lastOpens {
-					if atomic.AddInt32(this.ptr, this.step) >= maxOpenFilesValue {
-						atomic.StoreInt32(this.ptr, maxOpenFilesValue)
-					}
-				}
-				this.lastOpens = currentOpens
-				atomic.StoreInt32(&this.currentOpens, 0)
-			}
-
 			// reset mode
-			atomic.StoreInt32(&this.mode, 0)
+			atomic.StoreInt32(&this.mode, modeFast)
 		}
 	})
 }
 
 func (this *MaxOpenFiles) Fast() {
-	if atomic.LoadInt32(&this.mode) == 0 {
-		this.mode = modeFast
-	}
-	atomic.AddInt32(&this.currentOpens, 1)
+	atomic.AddInt32(&this.mode, modeFast)
+}
+
+func (this *MaxOpenFiles) FinishAll() {
+	this.Fast()
 }
 
 func (this *MaxOpenFiles) Slow() {
 	atomic.StoreInt32(&this.mode, modeSlow)
 }
 
-func (this *MaxOpenFiles) Max() int32 {
-	if atomic.LoadInt32(&this.mode) == modeSlow {
-		return 0
-	}
-
-	var v = atomic.LoadInt32(this.ptr)
-	if v <= minOpenFilesValue {
-		return minOpenFilesValue
-	}
-	return v
+func (this *MaxOpenFiles) Next() bool {
+	return atomic.LoadInt32(&this.mode) != modeSlow
 }
diff --git a/internal/caches/max_open_files_test.go b/internal/caches/max_open_files_test.go
index 814d21d..2b37ab4 100644
--- a/internal/caches/max_open_files_test.go
+++ b/internal/caches/max_open_files_test.go
@@ -9,20 +9,27 @@ import (
 )
 
 func TestNewMaxOpenFiles(t *testing.T) {
-	var maxOpenFiles = caches.NewMaxOpenFiles(2)
+	var maxOpenFiles = caches.NewMaxOpenFiles()
 	maxOpenFiles.Fast()
-	t.Log(maxOpenFiles.Max())
+	t.Log("fast:", maxOpenFiles.Next())
+
+	maxOpenFiles.Slow()
+	t.Log("slow:", maxOpenFiles.Next())
+	time.Sleep(1*time.Second + 1*time.Millisecond)
+	t.Log("slow 1 second:", maxOpenFiles.Next())
+
+	maxOpenFiles.Slow()
+	t.Log("slow:", maxOpenFiles.Next())
+
+	maxOpenFiles.Slow()
+	t.Log("slow:", maxOpenFiles.Next())
 
-	maxOpenFiles.Fast()
 	time.Sleep(1 * time.Second)
-	t.Log(maxOpenFiles.Max())
+	t.Log("slow 1 second:", maxOpenFiles.Next())
 
 	maxOpenFiles.Slow()
-	t.Log(maxOpenFiles.Max())
+	t.Log("slow:", maxOpenFiles.Next())
 
-	maxOpenFiles.Slow()
-	t.Log(maxOpenFiles.Max())
-
-	maxOpenFiles.Slow()
-	t.Log(maxOpenFiles.Max())
+	maxOpenFiles.Fast()
+	t.Log("fast:", maxOpenFiles.Next())
 }
diff --git a/internal/caches/storage_file.go b/internal/caches/storage_file.go
index bee5cb2..321fedc 100644
--- a/internal/caches/storage_file.go
+++ b/internal/caches/storage_file.go
@@ -63,7 +63,7 @@ const (
 var sharedWritingFileKeyMap = map[string]zero.Zero{} // key => bool
 var sharedWritingFileKeyLocker = sync.Mutex{}
 
-var maxOpenFiles = NewMaxOpenFiles(2)
+var maxOpenFiles = NewMaxOpenFiles()
 
 const maxOpenFilesSlowCost = 500 * time.Microsecond // 0.5ms
 
@@ -428,7 +428,7 @@ func (this *FileStorage) openWriter(key string, expiredAt int64, status int, siz
 		return nil, ErrFileIsWriting
 	}
 
-	if !isFlushing && len(sharedWritingFileKeyMap) >= int(maxOpenFiles.Max()) {
+	if !isFlushing && !maxOpenFiles.Next() {
 		sharedWritingFileKeyLocker.Unlock()
 		return nil, ErrTooManyOpenFiles
 	}
@@ -439,6 +439,9 @@ func (this *FileStorage) openWriter(key string, expiredAt int64, status int, siz
 		if !isOk {
 			sharedWritingFileKeyLocker.Lock()
 			delete(sharedWritingFileKeyMap, key)
+			if len(sharedWritingFileKeyMap) == 0 {
+				maxOpenFiles.FinishAll()
+			}
 			sharedWritingFileKeyLocker.Unlock()
 		}
 	}()
@@ -608,12 +611,18 @@ func (this *FileStorage) openWriter(key string, expiredAt int64, status int, siz
 		return NewPartialFileWriter(writer, key, expiredAt, isNewCreated, isPartial, partialBodyOffset, ranges, func() {
 			sharedWritingFileKeyLocker.Lock()
 			delete(sharedWritingFileKeyMap, key)
+			if len(sharedWritingFileKeyMap) == 0 {
+				maxOpenFiles.FinishAll()
+			}
 			sharedWritingFileKeyLocker.Unlock()
 		}), nil
 	} else {
 		return NewFileWriter(this, writer, key, expiredAt, -1, func() {
 			sharedWritingFileKeyLocker.Lock()
 			delete(sharedWritingFileKeyMap, key)
+			if len(sharedWritingFileKeyMap) == 0 {
+				maxOpenFiles.FinishAll()
+			}
 			sharedWritingFileKeyLocker.Unlock()
 		}), nil
 	}