glog.go
func (l *Log) putBuffer(b *buffer) {
	if b.Len() >= 256 {
		// Let big buffers die a natural death.
		return
	}
	l.freeListMu.Lock()
	b.next = l.freeList
	l.freeList = b
	l.freeListMu.Unlock()
}
func (l *Log) putBuffer(b *buffer) {
	if b.Len() >= 256 {
		// Let big buffers die a natural death.
		return
	}
	l.freeListMu.Lock()
	b.next = l.freeList
	l.freeList = b
	l.freeListMu.Unlock()
}
// putBuffer returns a buffer to the free list.