From 3a19eea97c0456578eaef0bf31b136e5a7c3cb5e Mon Sep 17 00:00:00 2001
From: Chris Lu <chris.lu@gmail.com>
Date: Sat, 27 Nov 2021 12:13:00 -0800
Subject: [PATCH] allocate memory by slabs

---
 weed/util/mem/slot_pool.go      | 44 +++++++++++++++++++++++++++++++++
 weed/util/mem/slot_pool_test.go | 37 +++++++++++++++++++++++++++
 2 files changed, 81 insertions(+)
 create mode 100644 weed/util/mem/slot_pool.go
 create mode 100644 weed/util/mem/slot_pool_test.go

diff --git a/weed/util/mem/slot_pool.go b/weed/util/mem/slot_pool.go
new file mode 100644
index 000000000..e6680d3cb
--- /dev/null
+++ b/weed/util/mem/slot_pool.go
@@ -0,0 +1,44 @@
+package mem
+
+import "sync"
+
+var pools []*sync.Pool
+
+const (
+	min_size = 1024
+)
+
+func bitCount(size int) (count int) {
+	for ; size > min_size; count++ {
+		size = size >> 1
+	}
+	return
+}
+
+func init() {
+	// 1KB ~ 256MB
+	pools = make([]*sync.Pool, bitCount(1024*1024*256))
+	for i := 0; i < len(pools); i++ {
+		slotSize := 1024 << i
+		pools[i] = &sync.Pool{
+			New: func() interface{} {
+				buffer := make([]byte, slotSize)
+				return &buffer
+			},
+		}
+	}
+}
+
+func getSlotPool(size int) *sync.Pool {
+	index := bitCount(size)
+	return pools[index]
+}
+
+func Allocate(size int) []byte {
+	slab := *getSlotPool(size).Get().(*[]byte)
+	return slab[:size]
+}
+
+func Free(buf []byte) {
+	getSlotPool(cap(buf)).Put(&buf)
+}
diff --git a/weed/util/mem/slot_pool_test.go b/weed/util/mem/slot_pool_test.go
new file mode 100644
index 000000000..114951522
--- /dev/null
+++ b/weed/util/mem/slot_pool_test.go
@@ -0,0 +1,37 @@
+package mem
+
+import (
+	"testing"
+)
+
+func TestAllocateFree(t *testing.T) {
+	buf := Allocate(12)
+	Free(buf)
+	if cap(buf) != min_size {
+		t.Errorf("min size error allocated capacity=%d", cap(buf))
+	}
+	if len(buf) != 12 {
+		t.Errorf("size error")
+	}
+
+	buf = Allocate(4883)
+	Free(buf)
+	if cap(buf) != 1024<<bitCount(4883) {
+		t.Errorf("min size error allocated capacity=%d", cap(buf))
+	}
+	if len(buf) != 4883 {
+		t.Errorf("size error")
+	}
+
+}
+
+func TestBitCount(t *testing.T) {
+	count := bitCount(12)
+	if count != 0 {
+		t.Errorf("bitCount error count=%d", count)
+	}
+	if count != bitCount(min_size) {
+		t.Errorf("bitCount error count=%d", count)
+	}
+
+}