Not necessarily if you build them right. Nintendo’s Switch is a true microkernel and, if it cost 200% performance, there’s no way it would be viable on a 2015 Tegra X1. The 200% thing is kind of a myth that doesn’t apply to modern practice - now it’s more like 10%.
As for 10% security - it’s more than 10%. Take my same example, the Switch. No bugs have been found to launch unapproved software in the last 4 years. There’s always the Secure Boot bug by NVIDIA in earlier consoles, but not even a WebKit bug will get you homebrew on a Switch. Kind of a big deal…
Another example of this would be Microsoft’s experiments with what would happen if an OS was built with all apps running in managed code - no compiled apps. Performance cost? They got it down to just 7% (though, admittedly, Midori never shipped, but it did host Bing in a few countries for a few years.)
As for 10% security - it’s more than 10%. Take my same example, the Switch. No bugs have been found to launch unapproved software in the last 4 years. There’s always the Secure Boot bug by NVIDIA in earlier consoles, but not even a WebKit bug will get you homebrew on a Switch. Kind of a big deal…
Another example of this would be Microsoft’s experiments with what would happen if an OS was built with all apps running in managed code - no compiled apps. Performance cost? They got it down to just 7% (though, admittedly, Midori never shipped, but it did host Bing in a few countries for a few years.)