[roca]

> RR wants fairly exclusive to the perf counters

No, it can get by with just one of the general-purpose counters, though two is preferable. Most modern Intel CPUs have at least four GP counters, plus some other dedicated counters for the most commonly used events (instructions, cycles).

> Also note that in Google's world, RR would probably not be compatible with how the tests are run anyway

That may well be true, but I suspect it's more likely to be some other issue, e.g. that the tests run in VMs that don't virtualize the PMU.

It's true that rr perturbs tests, making some bugs difficult to reproduce and making other bugs show up. However, a single failing run captured by rr is almost always enough to figure out the bug. We also have some techniques for randomizing perturbation (e.g. of scheduling) to expose a wider variety of bugs.