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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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