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

[Peter Zijlstra <peterz@infradead.org>]

> 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 )

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.