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fwd: Scheduler activations (IIRC) question

Jamie Lokier is heading down the KSE / kernel activations
pathway because he still thinks kernel threads are wrong.
The discussion is under the subject "Scheduler activations (IIRC) question":

"It isn't reasonable to make a kernel thread per userspace state
machine: I want less preemption than that implies, having more control
over locking contexts between the state machines than that.  And each
kernel thread uses a relatively large space, while the states are
quite small and it is reasonable to have a large number."

Maybe someone familiar with NPTL (or the drawbacks in NGPT) can straighten him out there?
I guess it'd be just as good to let him try to implement
scheduler activations with futexes.  It'd be a fun show.

"As you can see, this achieves asynchronous system calls which are too
complex for aio(*), best use of the I/O elevator, and 100% CPU
utilisation doing useful calculations."

"Plus AIO link(), unlink(), rename(), open() (especially open),
msync(), mlock(), mmap(), sendfile(), readdir(), readlink(), ioctl()
and a few more."

Maybe someone familiar with the state of AIO could comment?


Dan Kegel

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