We are considering using an equity rollover, and are trying to understand what IRR is used to calculate the performance bonus?

If we consider the simplified case where the EV = 10m, Vendor Equity rollover = 2m (20% equity), Investors = 3m, Senior Debt = 5m.

When we consider the performance bonus for the Searcher, is it calculated on the Investors IRR, or the overall investors (including the vendor) or is it something else?