Re: Externalize SLIT table

Matthew Dobson
2004-11-10T22:09:20Z

On Wed, 2004-11-10 at 10:45, Erich Focht wrote:
> On Wednesday 10 November 2004 06:05, Mark Goodwin wrote:
> > On a system that has nodes with multiple sockets (each supporting
> > multiple cores or HT "CPUs" sharing some level of cache), when the
> > scheduler needs to migrate a task it would first choose a CPU
> > sharing the same cache, then a CPU on the same node, then an
> > off-node CPU (i.e. falling back to node distance).
>
> This should be done by correctly setting up the sched domains. It's
> not a question of exporting useless or redundant information to user
> space.
>
> The need for some (any) cpu-to-cpu metrics initially brought up by
> Jack seemed mainly motivated by existing user space tools for
> constructing cpusets (maybe in PBS). I think it is a tolerable effort
> to introduce in user space an inlined function or macro doing
> something like
> cpu_metric(i,j) := node_metric(cpu_node(i),cpu_node(j))
>
> It keeps the kernel free of misleading information which might just
> slightly make cpusets construction more comfortable. In user space you
> have the full freedom to enhance your metrics when getting more
> details about the next generation cpus.

Good point, Erich. I don't think there is any desperate need for
CPU-to-CPU distances to be exported to userspace right now. If that is
incorrect and someone really needs a particular distance metric to be
exported by the kernel, we can look into that and export the required
info. For now I think the Node-to-Node distance information is enough.
-Matt