Wasted a bunch of time testing some instances and eventually gave up on figuring out why the results looked weird compared to other similar instances.. The vendor finally came back and said it was because their OS image had "irqbalance" disabled by default, which caused the IO to stack up on cpu0 and make the ACT results look bad. After two weeks of back and forth, finally came to that conclusion and with irqbalance enabled things look sane.

Because having irqbalance can badly hurt IO performance, can we add a warning to ACT to tell the end user if irqbalance is disabled? Obviously this could be intended but a warning might be a good idea.