more code

internal/cache/lru.go

@@ -22,8 +22,10 @@ type LRU struct {
 	shards []*shard
 	mask   uint64
 
-	// perShard is the per-shard entry budget.
-	perShard int
+	// perShard is the per-shard entry budget. It is atomic because a config
+	// reload resizes the cache from the API goroutine while queries are
+	// inserting in every shard.
+	perShard atomic.Int64
 
 	// counters are the hot-path stats, kept as atomics so Get does not need
 	// the lock just to record a hit.
@@ -69,13 +71,10 @@ func NewLRU(size, shards int) *LRU {
 	l := &LRU{
 		shards:       make([]*shard, shards),
 		mask:         uint64(shards - 1),
-		perShard:     size / shards,
 		seed:         maphash.MakeSeed(),
 		prefetchGate: make(chan struct{}, 64),
 	}
-	if l.perShard < 1 {
-		l.perShard = 1
-	}
+	l.perShard.Store(int64(max(1, size/shards)))
 	for i := range l.shards {
 		l.shards[i] = &shard{
 			items: make(map[Key]*list.Element, 1024),
@@ -140,7 +139,7 @@ func (l *LRU) Get(k Key, now time.Time) (e *Entry, kind HitKind) {
 	}
 	s.mu.Unlock()
 
-	e.Hits++
+	e.Hits.Add(1)
 	if kind == Fresh {
 		l.hits.Add(1)
 	} else {
@@ -171,7 +170,8 @@ func (l *LRU) Put(k Key, e *Entry) {
 	s.bytes += e.Bytes
 	l.bytes.Add(int64(e.Bytes))
 	var dropped int
-	for s.ll.Len() > l.perShard {
+	budget := int(l.perShard.Load())
+	for s.ll.Len() > budget {
 		oldest := s.ll.Back()
 		if oldest == nil {
 			break
@@ -347,7 +347,7 @@ func (l *LRU) Stats() LRUStats {
 		Expired:   l.expired.Load(),
 		HitRate:   rate,
 		Shards:    len(l.shards),
-		Capacity:  l.perShard * len(l.shards),
+		Capacity:  int(l.perShard.Load()) * len(l.shards),
 	}
 }
 
@@ -358,5 +358,5 @@ func (l *LRU) SetCapacity(size, shards int) {
 		shards = len(l.shards)
 	}
 	shards = roundPow2(shards)
-	l.perShard = max(1, size/shards)
+	l.perShard.Store(int64(max(1, size/shards)))
 }