* Christoph Hellwig <[email protected]> wrote:
> I tend to agree. Note that there is one thing we should be doing one
> one day (not only if we want to use it for aio) is to make kernel
> threads more lightweight. There a lot of baggae we keep around in
> task_struct and co that only makes sense for threads that have a user
> space part and aren't or shouldn't be needed for a purely
> kernel-resistant thread.
yeah. I'm totally open to such efforts. I'd also be most happy if this
was primarily driven via the KAIO effort: i.e. to implement it via
kernel threads and then to benchmark the hell out of it. I volunteer to
fix whatever fat kernel thread handling has left.
and if people agree with me that 'native' state-machine driven KAIO is
where we want to ultimately achieve (it is certainly the best performing
implementation) then i dont see the point in fibrils as an interim
mechanism anyway. Lets just hide AIO complexities from userspace via
kernel threads, and optimize this via two methods: by making kernel
threads faster, and by simultaneously and gradually converting as much
KAIO code to a native state machine - which would not need any kind of
kernel thread help anyway.
(plus as i mentioned previously, co-scheduling kernel threads with
related user space threads on the same CPU might be something useful too
- not just for KAIO, and we could add that too.)
also, we context-switch kernel threads in 350 nsecs on current hardware
and the -rt kernel is certainly happy with that and runs all hardirqs
and softirqs in separate kernel thread contexts. There's not /that/ much
fat left to cut off - and if there's something more to optimize there
then there are a good number of projects interested in that, not just
the KAIO effort :)
Ingo
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