From b36388035a87c3ee500dc6c9a53adb0de70700ff Mon Sep 17 00:00:00 2001
From: Nick Pillitteri <nick.pillitteri@grafana.com>
Date: Thu, 29 Feb 2024 13:56:32 -0500
Subject: [PATCH] Allocate map for results to hold expected number of keys

Pre-allocate the map used for results based on the number of keys
being fetched. Not needing to grow the map as results are added
results in a 5-10% performance improvement in local benchmarking.
---
 memcache/memcache.go      |  2 +-
 memcache/memcache_test.go | 27 +++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/memcache/memcache.go b/memcache/memcache.go
index c5962d0..c627cbd 100644
--- a/memcache/memcache.go
+++ b/memcache/memcache.go
@@ -619,7 +619,7 @@ func (c *Client) GetMulti(keys []string, opts ...Option) (map[string]*Item, erro
 	options := newOptions(opts...)
 
 	var lk sync.Mutex
-	m := make(map[string]*Item)
+	m := make(map[string]*Item, len(keys))
 	addItemToMap := func(it *Item) {
 		lk.Lock()
 		defer lk.Unlock()
diff --git a/memcache/memcache_test.go b/memcache/memcache_test.go
index 97f7780..8694066 100644
--- a/memcache/memcache_test.go
+++ b/memcache/memcache_test.go
@@ -539,6 +539,33 @@ func TestClient_Close_ShouldBeIdempotent(t *testing.T) {
 	c.Close()
 }
 
+func BenchmarkGetMulti(b *testing.B) {
+	c := New(testServer)
+	defer c.Close()
+
+	var keys []string
+	for i := 0; i < 100; i++ {
+		key := fmt.Sprintf("bench-%d", i)
+		keys = append(keys, key)
+
+		err := c.Set(&Item{
+			Key:        key,
+			Value:      []byte(strings.Repeat("bench payload", 10)),
+			Flags:      0,
+			Expiration: 30,
+			casid:      0,
+		})
+		if err != nil {
+			b.Fatal("Could not set item for test server: ", err)
+		}
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, _ = c.GetMulti(keys)
+	}
+}
+
 func BenchmarkOnItem(b *testing.B) {
 	fakeServer, err := net.Listen("tcp", "localhost:0")
 	if err != nil {