The CPU is only contended once it's at 100%. I am not aware of any interactive server (as opposed to batch processing) that behaves well at 100% CPU (beyond sho

The CPU is only contended once it's at 100%. I am not aware of any interactive server (as opposed to batch processing) that behaves well at 100% CPU (beyond short bursts), so I think that the hope you can actually balance the CPU using the OS scheduler (which isn't all that good) to produce good outcomes at 100% CPU is more myth than reality. So yes, I'm talking about resources accessed via IO, because there isn't all that much you can do about a CPU that's at 100% for long durations other than getting more CPU (horizontally or vertically). However, when you have some background batch computational tasks of some limited concurrency (otherwise you'd be in trouble) then you should have some low-priority platform threads servicing that. Virtual threads work due to Little's law by allowing a high number of threads. For such low-priority background tasks you probably want a very low number of threads (often one), so the ability to have tens of thousands, or millions, of virtual threads won't help you for those background tasks anyway.