Re: [Lse-tech] Re: [patch] scheduler fix for 1cpu/node case

[Nick Piggin]

Andrew Theurer wrote:

> On Wednesday 13 August 2003 15:49, Bill Davidsen wrote:
>
> > On Mon, 28 Jul 2003, Andrew Theurer wrote:
> >
> > > Personally, I'd like to see all systems use NUMA sched, non NUMA systems
> > > being a single node (no policy difference from non-numa sched), allowing
> > > us to remove all NUMA ifdefs.  I think the code would be much more
> > > readable.
> > That sounds like a great idea, but I'm not sure it could be realized short
> > of a major rewrite. Look how hard Ingo and Con are working just to get a
> > single node doing a good job with interactive and throughput tradeoffs.
>
> Actually it's not too bad.  Attached is a patch to do it.  It also does 
> multi-level node support and makes all the load balance routines 
> runqueue-centric instead of cpu-centric, so adding something like shared 
> runqueues (for HT) should be really easy.  Hmm, other things: inter-node 
> balance intervals are now arch specific (AMD is "1").  The default busy/idle 
> balance timers of 200/1 are not arch specific, but I'm thinking they should 
> be.  And for non-numa, the scheduling policy is the same as it was with 
> vanilla O(1). 

I'm not saying you're wrong, but do you have some numbers where this
helps? ie. two architectures that need very different balance numbers.
And what is the reason for making AMD's balance interval 1?

Also, things like nr_running_inc are supposed to be very fast. I am
a bit worried to see a loop and CPU shared atomics in there.

node_2_node is an odd sounding conversion too ;)

BTW. you should be CC'ing Ingo if you have any intention of scheduler
stuff getting into 2.6.


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