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    SubjectRe: [Lse-tech] [PATCH] cpusets - big numa cpu and memory placement
    On Tue, 5 Oct 2004, Paul Jackson wrote:

    > Matthew wrote:
    > >
    > > By adding locking and reference counting, and simplifying the way in which
    > > sched_domains are created, linked, unlinked and eventually destroyed we
    > > can use sched_domains as the implementation of cpusets.
    > I'd be inclined to turn this sideways from what you say.
    > Rather, add another couple of properties to cpusets:
    > 1) An isolated flag, that guarantees whatever isolation properties
    > we agree that schedulers, allocators and resource allocators
    > require between domains, and
    > 2) For those cpusets which are so isolated, the option to add
    > links of some form, between that cpuset, and distinct scheduler,
    > allocator and/or resource domains.

    Just to make sure we speak the same language:

    That would lead to three kinds of cpusets:

    1-'isolated' cpusets, with maybe a distinct scheduler, allocator and/or
    resource domains.

    2-'exclusive' cpusets (maybe with a better name?), that just don't overlap
    with other cpusets who have the same parent.

    3-'non-exclusive, non isolated' cpusets, with no restriction of any kind.

    I suppose it would still be possible to create cpusets of type 2 or 3
    inside a type-1 cpuset. They would be managed by the scheduler of the
    parent 'isolated' cpuset.

    I was thinking that the top cpuset is a particular case of type-1, but
    actually no.

    'isolated' cpusets should probably be at the same level as the top cpuset
    (who should lose this name, then).

    How should 'isolated' cpusets be created ? Should the top_cpuset be shrunk
    to free some CPUs so we have room to create a new 'isolated' cpuset ?

    Or should 'isolated' cpusets stay inside the top cpuset, that whould have
    to schedule its processes outside the 'isolated' cpusets ? Should it then
    be forbidden to cover the whole system with 'isolated' cpusets ?

    That's a lot of question marks...
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