Re: kernel thread support - LWP's

Donald Sharp (sharpd@cisco.com)
Thu, 15 Jul 1999 13:11:59 -0400


On Thu, Jul 15, 1999 at 08:50:02AM -0700, Nate Tuck wrote:
> At 12:31 AM 7/15/99 -0600, Larry McVoy wrote:
> >Second, for those rare cases where they actually do cost too much,
> >that's only on crappy operating systems. The last time I checked, Linux
> >process context switches were faster than Solaris LWP context switches.
> >So much for that argument.
>
> Larry,
>
> Since you've obviously talked to a lot of good people on this, I was
> wondering if you could talk about the only issue I haven't heard you bring
> up which is frequently brought up by the LWP/user-thread-scheduler folks.
> What about kernel run-queue length? It seems that I've heard the argument
> made that LWP's keep you from spending a long time in the kernel scheduler,
> which I could see might actually be a good thing.
>

I have never understood this arguement. With LWP's you have to spend
time in 2 schedulers: The kernel's and the Thread libraries. I guess
they might be able to claim that the thread libraries scheduler is much
much faster than the kernel's scheduler, so you end up with a bonus.

donald

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