Re: Linux Preemptive patch success 2.4.10-pre4 + lots of other

[Robert Love]

On Fri, 2001-09-07 at 01:19, Daniel Phillips wrote:
> On September 7, 2001 06:45 am, Robert Love wrote:
> > On Fri, 2001-09-07 at 00:36, Christoph Lameter wrote:
> > > Given the minimal nature of the patch I would suggest that it become part
> > > of 2.4.10 or 11
> > 
> > Are you kidding?  We will be lucky to see this in during 2.5.
> > Its a pretty big change.  It makes the Linux kernel preemptible.
> 
> CONFIG_PREEMPT

and... ?

> > This is a fairly big move, one I don't think any of the major Unices have
> > done.
> 
> The other Unices are at least evenly split, or mostly preemptible.
> Typically, a more complex strategy is used where spinlocks can sleep
> after a few spins.  This patch is very conservative in that regard,
> it basically just uses the structure we already have, SMP spinlocks.

I did not know other Unices were (in general) preemptible.  Solaris is?
The only one I thought was preemptible was Irix.

Anyhow, you are right about the simplistic approach we take.  There are
a few alternatives: mixing mutexes and shorter locks, priority-bearing
semaphores, changing the way the preemption count works, etc.

> > The only reason the patch is not _huge_ is because the Linux
> > kernel is already setup for concurrency of this nature -- it does SMP.
> > 
> > I suggest you read
> > http://www.linuxdevices.com/articles/AT4185744181.html
> > http://www.linuxdevices.com/articles/AT5152980814.html
> > http://kpreempt.sourceforge.net
> > 
> > and my previous threads on this issue, for more informaiton.
> 
> Hmm, how did you read those and come to such a different conclusion?

What different conclusion? What are you even arguing with me about? 

Do you think I am against a preemptible kernel?  I _posted_ the damn
patch, of course I am not.

I probably agree with whatever you are thinking.

-- 
Robert M. Love
rml at ufl.edu
rml at tech9.net