RB_ALIGNMENT
#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
length = event->type_len * RB_ALIGNMENT;
event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
length += RB_ALIGNMENT;