> Memory is also not a problem since all modern operating system allocates stack memory as needed.
A modern OS can only allocate memory as needed with a page-level granularity.
For many millions of threads, this is not good enough and will waste GB's of memory completely unnecessarily. Maybe in a decade wasting GB's of memory will be negligible (but then we might want trillions of threads!). And pages seem to be growing too, so the OS granularity is too coarse for micro-threads.
A modern OS can only allocate memory as needed with a page-level granularity.
For many millions of threads, this is not good enough and will waste GB's of memory completely unnecessarily. Maybe in a decade wasting GB's of memory will be negligible (but then we might want trillions of threads!). And pages seem to be growing too, so the OS granularity is too coarse for micro-threads.