code: 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()
  }
docs: // putBuffer returns a buffer to the free list.