Would cause much performance degradation where it matters most. I run some heavy jobs today. Many CPU seconds each. I don't see that those have to suffer. They

Would cause much performance degradation where it matters most. I run some heavy jobs today. Many CPU seconds each. I don't see that those have to suffer. They can stay married to a CPU core for seconds at a time, uninterrupted, just like today. They perform few system calls, and the ones they do perform never fail any in-kernel check. The javascript that runs in the browser suffers, sure, but that javascript has other reasons not to need several seconds of CPU. BTW, that person was me, and you misunderstand the question. Not into a privileged state. Out of. Such that an unprivileged/unstrusted process would see cache contents produced by others.