Homework: radixvm question

Submit two items to the the submission web site:

Submit your own question about the paper (e.g., what you find most confusing about the paper or the paper's general context/problem) before 10pm the night before. You cannot use the question below. To the extent possible, during lecture we will try to answer questions submitted the evening before.
Submit your answer for the question below before the beginning of the lecture

Answer the following question: Refcache re-examines the reference count of an object two epochs later after it inserts the object in a per-core review queue (see page 4, 2nd paragraph, right column). What goes wrong if refcache reviews objects only one epoch later? Is two epochs later just more efficient or is it necessary for correctness? (Briefly explain your answer.)