If I remember correctly, this was the threading model used by Solaris. I'm sure there are many applications that make use of M:N threading, but for the server

If I remember correctly, this was the threading model used by Solaris. I'm sure there are many applications that make use of M:N threading, but for the server I worked on (~3000 concurrent connections and 50+ threads), this actually hindered the multi-tasking performance of the server. I remember investigating and figuring out this was the reason, and switching back to 1:1 made the performance increase.