[opt] nazabytes: 优化Buffer的扩容逻辑

.gitignore

@@ -1,6 +1,7 @@
 /pkg/websocket
 /pkg/tag
 /pkg/nazatime
+/pkg/congestion_control
 
 /playground
 /playground/cc
@@ -10,7 +11,8 @@
 /demo/temp
 /demo/analyse_git_log
 /demo/analyse_wireshark_plain_txt_dissection
-/demo/disksweeper/
+/demo/disksweeper
+/demo/diskbackup
 
 /.idea
 /.trash

pkg/nazabytes/buffer.go

@@ -18,6 +18,7 @@ import (
 // TODO(chef): 增加options: growRoundThreshold; 是否做检查
 // TODO(chef): 扩容策略函数可由外部传入
 
+const growMinThreshold = 128
 const growRoundThreshold = 1048576 // 1MB
 
 // Buffer 先进先出可扩容流式buffer，可直接读写内部切片避免拷贝
@@ -133,14 +134,16 @@ func (b *Buffer) Grow(n int) {
 		return
 	}
 
+	// 预分配一些
+	if n <= growMinThreshold {
+		n = growMinThreshold
+	} else if n < growMinThreshold {
+		n = roundUpPowerOfTwo(n)
+	}
+
 	// 扩容后总共需要的大小
 	needed := b.Len() + n
 
-	// 扩容大小在阈值范围内时，向上取值到2的倍数
-	if needed < growRoundThreshold {
-		needed = roundUpPowerOfTwo(needed)
-	}
-
 	nazalog.Debugf("[%p] Buffer::Grow. realloc, n=%d, copy=%d, cap=(%d, %d)", b, n, b.Len(), b.Cap(), needed)
 	core := make([]byte, needed, needed)
 	copy(core, b.core[b.rpos:b.wpos])

pkg/nazabytes/buffer_test.go

@@ -47,9 +47,9 @@ func TestBuffer(t *testing.T) {
 	assert.Equal(t, golden, buf)
 	b.Skip(10)
 	assert.Equal(t, nil, b.Bytes())
-	assert.Equal(t, 16, len(b.WritableBytes()))
+	assert.Equal(t, 128, len(b.WritableBytes()))
 	assert.Equal(t, 0, b.Len())
-	assert.Equal(t, 16, b.Cap())
+	assert.Equal(t, 128, b.Cap())
 
 	// 利用头部空闲空间扩容
 	buf = b.ReserveBytes(10)
@@ -63,7 +63,7 @@ func TestBuffer(t *testing.T) {
 	assert.Equal(t, golden[2:], b.Bytes()[:8])
 	assert.Equal(t, golden[:7], b.Bytes()[8:])
 	assert.Equal(t, 15, b.Len())
-	assert.Equal(t, 16, b.Cap())
+	assert.Equal(t, 128, b.Cap())
 
 	// Truncate
 	b.Reset()