I&#x27;d say he&#x27;s half-right on the M:N scheduling.<p>For implementing POSIX threads, M:N threading has a lot of extra complexity and few advantages, and worse performance.<p>But if you don&#x27;t have POSIX threads, but something higher-level that&#x27;s managed by a runtime anyway, you don&#x27;t need to worry about things like ensuring enough VM space and at least one allocated page for each thread stack.<p>Erlang&#x27;s and GHC&#x27;s threads start out needing much less space than a single page, so you can start 10x more threads in the same amount of RAM.