[PATCH v4 5/5] sched: ARM: create a dedicated scheduler topology table

[Peter Zijlstra]

On Fri, Apr 25, 2014 at 06:04:19PM +0200, Peter Zijlstra wrote:
> > The example above is consistent because CPU2 mask and CPU0 mask are
> > fully exclusive
> > 
> > so
> > CPU0: cpu_corepower_mask=0-1
> > CPU2: cpu_corepower_mask=2
> > are consistent
> > 
> > CPU0: cpu_corepower_mask=0-2
> > CPU2: cpu_corepower_mask=0-2
> > are also consistent
> > 
> > but
> > 
> > CPU0: cpu_corepower_mask=0-1
> > CPU2: cpu_corepower_mask=0-2
> > are not consistent
> > 
> > and your example uses the last configuration
> > 
> > To be more precise, the rule above applies on default SDT definition
> > but the flag SD_OVERLAP enables such kind of overlap between group.
> > Have you tried it ?
> 
> I've never tried degenerate stuff with SD_OVERLAP, it might horribly
> explode -- its not actually meant to work.
> 
> The SD_OVERLAP comes from not fully connected NUMA topologies; suppose
> something like:
> 
>         0------1
>         |      |
>         |      |
>         2------3
> 
> or:
> 
>  ( 10 20 20  0 )
>  ( 20 10  0 20 )
>  ( 20  0 10 20 )
>  (  0 20 20 10 )

d'0h: s/0/30/

0 <-> 3 is 2 hops, too focused on the single hop case

> Your domain level that models the single-hop/20 distance has overlapping
> masks:
> 
> N0: 0-2
> N1: 0,1,3
> N2: 0,2,3
> N3: 1-3
> 
> I've never tried to construct a NUMA topology that would be overlapping
> and have redundant bits in.