fifo_mask
&buf->ents[buf->beg_idx & fifo_mask],
static int fifo_mask;
fifo_mask = entries_per_buf - 1;
save = &buf->ents[earliest & fifo_mask];
i = scan & fifo_mask;
buf->ents[buf->beg_idx & fifo_mask].ktr_timestamp;
&buf->ents[buf->beg_idx & fifo_mask],
ent = &buf->ents[buf->beg_idx & fifo_mask];
chain = fifo->array[fifo->ri & fifo_mask(xop)];
fifo->errors[fifo->wi & fifo_mask(xop)] = error;
fifo->array[fifo->wi & fifo_mask(xop)] = chain;
chain = fifo->array[fifo->ri & fifo_mask(xop)];
error = fifo->errors[fifo->ri & fifo_mask(xop)];