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


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