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    SubjectRe: [RFC/PATCH 2/4] cpuset: system sets
    Peter wrote:
    > A system set will be one that caters the
    > general purpose OS. This patch provides the infrastructure, but doesn't
    > actually provide any new functionality.
    > Typical functionality would be setting the IRQ affinity of unbound IRQs to
    > within the system set. And setting the affinity of unbounded kernel threads to
    > within the system set.

    "one that caters the general purpose OS" ... a tad terse on the
    documentation ;).

    I guess what you have is a new cpumask_t cpu_system_map, which is the
    union of the CPUs of all the cpusets marked 'system', where to a rough
    approximation the CPUs -not- in that cpumask are what we would have
    called the isolated CPUs by the old code?

    In any case, if this patch survives its birth, it will need an added
    change for some file in the Documentation directory.

    Could we get the term 'cpu' in the name 'system' somehow? Perhaps call
    this new cpuset flag 'cpus_system' or some such. Cpusets handles both
    CPU and memory configuration, and I make some effort to mark per-cpuset
    specific attributes that apply to only one of these with a prefix
    indicating to which they apply. The per-cpuset flag name 'system', by
    itself, would mean little to someone just listing the files in a cpuset

    In the rebuild_system_map() code, you have:
    + if (cpus_empty(*new_system_map))
    + BUG();

    ... what's to prevent simply turning off the 'system' (aka cpus_system)
    in the top cpuset, on a system with only that one cpuset, and hitting
    this BUG()?

    Overall I like this approach. I suspect you made a good choice in
    marking the non-isolated (aka system) CPUs, rather than the isolated
    CPUs. It seems clearer that way, in understanding the affects of
    overlapping cpusets with various markings.

    I won't rest till it's the best ...
    Programmer, Linux Scalability
    Paul Jackson <> 1.940.382.4214

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