>If this somehow does end up being a reproducible performance issue (I still suspect something more complicated is going on), I don't see how userspace could be

>If this somehow does end up being a reproducible performance issue (I still suspect something more complicated is going on), I don't see how userspace could be expected to mitigate a substantial perf regression in 7.0 that can only be mitigated by a default-off non-trivial functionality also introduced in 7.0.