Or maybe a new system call to allow a thread to temporarily enter a “performance mode” where it can only be scheduled on the powerful cores. Pinning sounds a bit too strict.
You can already pin to a set of cores instead of a single one. But anyway, my point is that currently userspace interacts directly with CPU features without intermediation from the kernel. So intel would have to think about how to coordinate with userspace too, not just rely on the kernel to patch things up (or not).
