Yes it does:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...

fair.c deadline.c rt.c

Alternatively, it might be a confusion between Linux and Windows.

https://technet.microsoft.com/en-us/library/aa175393(v=sql.8...

The Windows Database team has been using the "User Mode Scheduling" feature of Windows to implement custom scheduling for databases for some time.

Mainline, sure, but there are other kernel forks that do, such as the ck kernel.

If you read the page, it simply states that you can tweak the parameters of the existing scheduler, not replace it entirely.

The scheduling policies listed on the man page I linked share some generic kernel code, but I wouldn't classify them as the same scheduler. If you look inside the kernel/sched/ directory in the source, you'll find that an instance of `struct sched_class` is defined for each scheduler class. There are dl_sched_class, rt_sched_class, fair_sched_class, and idle_sched_class. You can see in `pick_next_task` in core.c that these class structs are iterated over, calling into each scheduler's own `pick_next_task`: http://elixir.free-electrons.com/linux/v4.13.9/source/kernel...

not to mention the fact that kernel devs knew about it as well, so the whole title of the article is a bit bunk