We've heard reports of auto-compactor compacting even already compacted vbuckets.
This may happen for example during rebalance where lots of bulk changes happen in just few vbuckets. We should be compacting just those vbuckets. But we currently compact everything, causing somewhat quadratic behavior on heavier rebalances.
"compactor is unable to catch up during XDCR" bug somewhere may be "it" or just related.