diff --git a/internal/client/client_batch.go b/internal/client/client_batch.go
index a23c373d4..4cddc86d4 100644
--- a/internal/client/client_batch.go
+++ b/internal/client/client_batch.go
@@ -110,12 +110,7 @@ func (b *batchCommandsBuilder) push(entry *batchCommandsEntry) {
 const highTaskPriority = 10
 
 func (b *batchCommandsBuilder) hasHighPriorityTask() bool {
-	item := b.entries.top()
-	if item == nil {
-		return false
-	}
-
-	return item.priority() >= highTaskPriority
+	return b.entries.highestPriority() >= highTaskPriority
 }
 
 // buildWithLimit builds BatchCommandsRequests and calls collect() for each valid entry.
@@ -123,36 +118,45 @@ func (b *batchCommandsBuilder) hasHighPriorityTask() bool {
 // The second is a map that maps forwarded hosts to requests.
 func (b *batchCommandsBuilder) buildWithLimit(limit int64, collect func(id uint64, e *batchCommandsEntry),
 ) (*tikvpb.BatchCommandsRequest, map[string]*tikvpb.BatchCommandsRequest) {
-	pending := b.entries.Len()
-	for count, i := int64(0), 0; i < pending; i++ {
-		e := b.entries.Pop().(*batchCommandsEntry)
-		if e.isCanceled() {
-			continue
-		}
-		if e.priority() < highTaskPriority {
-			count++
-			if count > limit {
-				b.push(e)
-				break
+	count := int64(0)
+	build := func(reqs []Item) {
+		for _, e := range reqs {
+			e := e.(*batchCommandsEntry)
+			if e.isCanceled() {
+				continue
+			}
+			if e.priority() < highTaskPriority {
+				count++
 			}
-		}
 
-		if collect != nil {
-			collect(b.idAlloc, e)
-		}
-		if e.forwardedHost == "" {
-			b.requestIDs = append(b.requestIDs, b.idAlloc)
-			b.requests = append(b.requests, e.req)
-		} else {
-			batchReq, ok := b.forwardingReqs[e.forwardedHost]
-			if !ok {
-				batchReq = &tikvpb.BatchCommandsRequest{}
-				b.forwardingReqs[e.forwardedHost] = batchReq
+			if collect != nil {
+				collect(b.idAlloc, e)
+			}
+			if e.forwardedHost == "" {
+				b.requestIDs = append(b.requestIDs, b.idAlloc)
+				b.requests = append(b.requests, e.req)
+			} else {
+				batchReq, ok := b.forwardingReqs[e.forwardedHost]
+				if !ok {
+					batchReq = &tikvpb.BatchCommandsRequest{}
+					b.forwardingReqs[e.forwardedHost] = batchReq
+				}
+				batchReq.RequestIds = append(batchReq.RequestIds, b.idAlloc)
+				batchReq.Requests = append(batchReq.Requests, e.req)
 			}
-			batchReq.RequestIds = append(batchReq.RequestIds, b.idAlloc)
-			batchReq.Requests = append(batchReq.Requests, e.req)
+			b.idAlloc++
+		}
+	}
+	for (count < limit && b.entries.Len() > 0) || b.hasHighPriorityTask() {
+		n := limit
+		if limit == 0 {
+			n = 1
+		}
+		reqs := b.entries.Take(int(n))
+		if len(reqs) == 0 {
+			break
 		}
-		b.idAlloc++
+		build(reqs)
 	}
 	var req *tikvpb.BatchCommandsRequest
 	if len(b.requests) > 0 {
@@ -175,7 +179,7 @@ func (b *batchCommandsBuilder) cancel(e error) {
 // reset resets the builder to the initial state.
 // Should call it before collecting a new batch.
 func (b *batchCommandsBuilder) reset() {
-	b.entries.clean()
+	b.entries.Clean()
 	// NOTE: We can't simply set entries = entries[:0] here.
 	// The data in the cap part of the slice would reference the prewrite keys whose
 	// underlying memory is borrowed from memdb. The reference cause GC can't release
@@ -397,16 +401,16 @@ func (a *batchConn) getClientAndSend() {
 		a.index = (a.index + 1) % uint32(len(a.batchCommandsClients))
 		target = a.batchCommandsClients[a.index].target
 		// The lock protects the batchCommandsClient from been closed while it's in use.
-		if c := a.batchCommandsClients[a.index]; c.tryLockForSend() {
-			if hasHighPriorityTask || c.sent.Load() <= c.maxConcurrencyRequestLimit.Load() {
+		c := a.batchCommandsClients[a.index]
+		if hasHighPriorityTask || c.sent.Load() <= c.maxConcurrencyRequestLimit.Load() {
+			if c.tryLockForSend() {
 				cli = c
 				break
 			} else {
 				reason = SendFailedReasonNoAvailableLimit
-				c.unlockForSend()
 			}
 		} else {
-			reason = SendFailedReasonTryLockForSendFail
+			reason = SendFailedReasonNoAvailableLimit
 		}
 	}
 	if cli == nil {
diff --git a/internal/client/client_test.go b/internal/client/client_test.go
index 8f95b6339..d4d22bfe6 100644
--- a/internal/client/client_test.go
+++ b/internal/client/client_test.go
@@ -730,18 +730,18 @@ func TestLimitConcurrency(t *testing.T) {
 		batch.reqBuilder.reset()
 	}
 
+	// highest priority task will be sent immediately, not limited by concurrency
 	{
 		batch.reqBuilder.push(&batchCommandsEntry{req: &tikvpb.BatchCommandsRequest_Request{}, pri: highTaskPriority})
 		batch.reqBuilder.push(&batchCommandsEntry{req: &tikvpb.BatchCommandsRequest_Request{}, pri: highTaskPriority - 1})
 		reqs, _ := batch.reqBuilder.buildWithLimit(0, func(_ uint64, _ *batchCommandsEntry) {})
 		re.Len(reqs.RequestIds, 1)
-		re.Equal(1, batch.reqBuilder.len())
 		batch.reqBuilder.reset()
-		batch.reqBuilder.entries.Reset()
+		re.Equal(1, batch.reqBuilder.len())
 	}
 
+	// medium priority tasks are limited by concurrency
 	{
-		batch.reqBuilder.push(&batchCommandsEntry{req: &tikvpb.BatchCommandsRequest_Request{}})
 		batch.reqBuilder.push(&batchCommandsEntry{req: &tikvpb.BatchCommandsRequest_Request{}})
 		batch.reqBuilder.push(&batchCommandsEntry{req: &tikvpb.BatchCommandsRequest_Request{}})
 		reqs, _ := batch.reqBuilder.buildWithLimit(2, func(_ uint64, _ *batchCommandsEntry) {})
@@ -750,6 +750,14 @@ func TestLimitConcurrency(t *testing.T) {
 		batch.reqBuilder.reset()
 	}
 
+	// the expired tasks should be removed from the queue.
+	{
+		batch.reqBuilder.push(&batchCommandsEntry{req: &tikvpb.BatchCommandsRequest_Request{}, canceled: 1})
+		batch.reqBuilder.push(&batchCommandsEntry{req: &tikvpb.BatchCommandsRequest_Request{}, canceled: 1})
+		batch.reqBuilder.reset()
+		re.Equal(1, batch.reqBuilder.len())
+	}
+
 }
 
 func TestPrioritySentLimit(t *testing.T) {
diff --git a/internal/client/priority_queue.go b/internal/client/priority_queue.go
index 5e8b80db9..d89da66a3 100644
--- a/internal/client/priority_queue.go
+++ b/internal/client/priority_queue.go
@@ -87,16 +87,43 @@ func (pq *PriorityQueue) Push(item Item) {
 	heap.Push(&pq.ps, entry{entry: item})
 }
 
-// Pop removes the highest priority entry from the priority queue.
-func (pq *PriorityQueue) Pop() Item {
-	return heap.Pop(&pq.ps).(entry).entry
+// pop removes the highest priority entry from the priority queue.
+func (pq *PriorityQueue) pop() Item {
+	e := heap.Pop(&pq.ps)
+	if e == nil {
+		return nil
+	}
+	return e.(entry).entry
 }
 
-func (pq *PriorityQueue) top() Item {
-	if pq.Len() == 0 {
+// Take returns the highest priority entries from the priority queue.
+func (pq *PriorityQueue) Take(n int) []Item {
+	if n <= 0 {
 		return nil
 	}
-	return pq.ps[0].entry
+	if n >= pq.Len() {
+		ret := make([]Item, pq.Len())
+		for i := 0; i < pq.Len(); i++ {
+			ret[i] = pq.ps[i].entry
+		}
+
+		pq.ps = pq.ps[:0]
+		return ret
+	} else {
+		ret := make([]Item, n)
+		for i := 0; i < n; i++ {
+			ret[i] = pq.pop()
+		}
+		return ret
+	}
+
+}
+
+func (pq *PriorityQueue) highestPriority() uint64 {
+	if pq.Len() == 0 {
+		return 0
+	}
+	return pq.ps[0].entry.priority()
 }
 
 // All returns all entries in the priority queue not ensure the priority.
@@ -108,11 +135,13 @@ func (pq *PriorityQueue) All() []Item {
 	return items
 }
 
-func (pq *PriorityQueue) clean() {
-	for i := 0; i < pq.Len(); i++ {
+func (pq *PriorityQueue) Clean() {
+	for i := 0; i < pq.Len(); {
 		if pq.ps[i].entry.isCanceled() {
 			heap.Remove(&pq.ps, pq.ps[i].index)
+			continue
 		}
+		i++
 	}
 }
 
diff --git a/internal/client/priority_queue_test.go b/internal/client/priority_queue_test.go
index a7b1a2952..8f0b87f2d 100644
--- a/internal/client/priority_queue_test.go
+++ b/internal/client/priority_queue_test.go
@@ -21,8 +21,9 @@ import (
 )
 
 type FakeItem struct {
-	pri   uint64
-	value int
+	pri      uint64
+	value    int
+	canceled bool
 }
 
 func (f *FakeItem) priority() uint64 {
@@ -30,19 +31,43 @@ func (f *FakeItem) priority() uint64 {
 }
 
 func (f *FakeItem) isCanceled() bool {
-	return false
+	return f.canceled
 }
 
 func TestPriority(t *testing.T) {
 	re := require.New(t)
-	pq := NewPriorityQueue()
-	for i := 1; i <= 5; i++ {
-		pq.Push(&FakeItem{value: i, pri: uint64(i)})
-	}
-	re.Equal(5, pq.Len())
-	arr := pq.All()
-	re.Len(arr, 5)
-	for i := pq.Len(); i > 0; i-- {
-		re.Equal(i, pq.Pop().(*FakeItem).value)
+	testFunc := func(aq *PriorityQueue) {
+		for i := 1; i <= 5; i++ {
+			aq.Push(&FakeItem{value: i, pri: uint64(i)})
+		}
+		re.Equal(5, aq.Len())
+		re.Equal(uint64(5), aq.highestPriority())
+		aq.Clean()
+		re.Equal(5, aq.Len())
+
+		arr := aq.Take(1)
+		re.Len(arr, 1)
+		re.Equal(uint64(5), arr[0].priority())
+		re.Equal(uint64(4), aq.highestPriority())
+
+		arr = aq.Take(2)
+		re.Len(arr, 2)
+		re.Equal(uint64(4), arr[0].priority())
+		re.Equal(uint64(3), arr[1].priority())
+		re.Equal(uint64(2), aq.highestPriority())
+
+		arr = aq.Take(5)
+		re.Len(arr, 2)
+		re.Equal(uint64(2), arr[0].priority())
+		re.Equal(uint64(1), arr[1].priority())
+		re.Equal(uint64(0), aq.highestPriority())
+		re.Equal(0, aq.Len())
+
+		aq.Push(&FakeItem{value: 1, pri: 1, canceled: true})
+		re.Equal(1, aq.Len())
+		aq.Clean()
+		re.Equal(0, aq.Len())
 	}
+	hq := NewPriorityQueue()
+	testFunc(hq)
 }