From 604b0d6d4537d06f58a7f46aa9d722963354ce4c Mon Sep 17 00:00:00 2001
From: Ryan Leung <rleungx@gmail.com>
Date: Fri, 17 Jan 2025 16:47:52 +0800
Subject: [PATCH] pkg: avoid make channel every time (#9009)

close tikv/pd#9004

Signed-off-by: Ryan Leung <rleungx@gmail.com>

Co-authored-by: ti-chi-bot[bot] <108142056+ti-chi-bot[bot]@users.noreply.github.com>
---
 pkg/ratelimit/option.go             | 36 +++++++++++++++++++----------
 pkg/utils/tsoutil/tso_dispatcher.go |  7 +++++-
 2 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/pkg/ratelimit/option.go b/pkg/ratelimit/option.go
index e6d4a4f8ff0..65bb86a4d56 100644
--- a/pkg/ratelimit/option.go
+++ b/pkg/ratelimit/option.go
@@ -37,30 +37,36 @@ type Option func(string, *Controller) UpdateStatus
 // AddLabelAllowList adds a label into allow list.
 // It means the given label will not be limited
 func AddLabelAllowList() Option {
-	return func(label string, l *Controller) UpdateStatus {
-		l.labelAllowList[label] = struct{}{}
+	return func(label string, c *Controller) UpdateStatus {
+		c.labelAllowList[label] = struct{}{}
 		return InAllowList
 	}
 }
 
 // UpdateConcurrencyLimiter creates a concurrency limiter for a given label if it doesn't exist.
 func UpdateConcurrencyLimiter(limit uint64) Option {
-	return func(label string, l *Controller) UpdateStatus {
-		if _, allow := l.labelAllowList[label]; allow {
+	return func(label string, c *Controller) UpdateStatus {
+		if _, allow := c.labelAllowList[label]; allow {
 			return InAllowList
 		}
-		lim, _ := l.limiters.LoadOrStore(label, newLimiter())
+		lim, loaded := c.limiters.Load(label)
+		if !loaded {
+			lim, _ = c.limiters.LoadOrStore(label, newLimiter())
+		}
 		return lim.(*limiter).updateConcurrencyConfig(limit)
 	}
 }
 
 // UpdateQPSLimiter creates a QPS limiter for a given label if it doesn't exist.
 func UpdateQPSLimiter(limit float64, burst int) Option {
-	return func(label string, l *Controller) UpdateStatus {
-		if _, allow := l.labelAllowList[label]; allow {
+	return func(label string, c *Controller) UpdateStatus {
+		if _, allow := c.labelAllowList[label]; allow {
 			return InAllowList
 		}
-		lim, _ := l.limiters.LoadOrStore(label, newLimiter())
+		lim, loaded := c.limiters.Load(label)
+		if !loaded {
+			lim, _ = c.limiters.LoadOrStore(label, newLimiter())
+		}
 		return lim.(*limiter).updateQPSConfig(limit, burst)
 	}
 }
@@ -71,18 +77,24 @@ func UpdateDimensionConfig(cfg *DimensionConfig) Option {
 		if _, allow := c.labelAllowList[label]; allow {
 			return InAllowList
 		}
-		lim, _ := c.limiters.LoadOrStore(label, newLimiter())
+		lim, loaded := c.limiters.Load(label)
+		if !loaded {
+			lim, _ = c.limiters.LoadOrStore(label, newLimiter())
+		}
 		return lim.(*limiter).updateDimensionConfig(cfg)
 	}
 }
 
 // InitLimiter creates empty concurrency limiter for a given label by config if it doesn't exist.
 func InitLimiter() Option {
-	return func(label string, l *Controller) UpdateStatus {
-		if _, allow := l.labelAllowList[label]; allow {
+	return func(label string, c *Controller) UpdateStatus {
+		if _, allow := c.labelAllowList[label]; allow {
 			return InAllowList
 		}
-		l.limiters.LoadOrStore(label, newLimiter())
+		_, loaded := c.limiters.Load(label)
+		if !loaded {
+			c.limiters.LoadOrStore(label, newLimiter())
+		}
 		return LimiterNotChanged
 	}
 }
diff --git a/pkg/utils/tsoutil/tso_dispatcher.go b/pkg/utils/tsoutil/tso_dispatcher.go
index be7d4fa6d83..c563358adfe 100644
--- a/pkg/utils/tsoutil/tso_dispatcher.go
+++ b/pkg/utils/tsoutil/tso_dispatcher.go
@@ -69,7 +69,12 @@ func (s *TSODispatcher) DispatchRequest(
 	doneCh <-chan struct{},
 	errCh chan<- error,
 	tsoPrimaryWatchers ...*etcdutil.LoopWatcher) {
-	val, loaded := s.dispatchChs.LoadOrStore(req.getForwardedHost(), make(chan Request, maxMergeRequests))
+	key := req.getForwardedHost()
+	val, loaded := s.dispatchChs.Load(key)
+	if !loaded {
+		val = make(chan Request, maxMergeRequests)
+		val, loaded = s.dispatchChs.LoadOrStore(key, val)
+	}
 	reqCh := val.(chan Request)
 	if !loaded {
 		tsDeadlineCh := make(chan *TSDeadline, 1)