The patch we wrote allows the fault handler to fully populate and promote a reservation once the number of non-resident 64K-aligned chunks (aka "holes") in the reservation falls below some threshold. The test makes Clang compile Dhrystone for 5000 times. The following figure shows how three hardware counters change as we increase the threshold (and thus making the promotion policy more aggressive). The rightmost point on the x axis is where we apply the "dd if=/usr/bin/clang of=/dev/null" trick, and end up getting 25 superpages out of clang's main executable region.