Hi!
> >>How does that work? Switching between kernel threads requires going into
> >>the kernel, user level thread switches are all done in user mode.
> >>
> >>Do you have some way to change o/s threads w/o going into the kernel?
> >>
> >
> >But going into kernel is not very expensive on Linux.
> >
> >On the other side, the overhead you need to add for every single syscall
> >that might block for the M:N threads and the associated complications
> >which make it far harder to conform to POSIX IMHO far outweight the costs
> >of going into the kernel for a context switch.
>
> That really wasn't my question, Arjan said that switching real threads
> wasn't a context switch in the hardware sense, and I was asking if I
> missed something. It may be cheap, but it would seem to be a context
> switch none-the-less.
It is not reloading %cr3.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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