Re: a joint letter on low latency and Linux

[Andi Kleen]

On Fri, Jun 30, 2000 at 08:36:06AM -0700, Larry McVoy wrote:
> > 	- Use Linus' trick of a multi threaded UP kernel using
> > 	  SMP locks (2.5 material), also hated by Larry/Victor.
> 
> I don't know where you got that idea.  Sun does the same thing and I've
> always held it up as a good thing, ``eat what you cook'' type of deal.
> The nice thing about doing that is that because of interrupts even a UP
> is really an MP, and you don't have to have two different models when
> doing SMP.
> 
> So I don't hate it.  I agree with Ted's comment that it would be nice if
> it were possible to have it both ways so as to be able to quantify the 
> effects, though I don't know how realistic that is.

A generally preemptible kernel with tons of locks is IMHO clearly one of 
these ``it is only 5-10% slower'' things that you criticized just a few
messages ago.  Next there will be scheduled interrupt threads, ugh :-/
(good for soft rt, but lots of overhead) 

-Andi