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    SubjectRe: [RFC] Cpuset: explicit dynamic sched domain control flags
    On Mon, Oct 16, 2006 at 04:03:51PM -0700, Paul Jackson wrote:
    > From: Paul Jackson <pj@sgi.com>
    >
    > I should get agreement from the other folks who care about the
    > interaction of cpusets and sched domains before submitting this
    > to Andrew for staging in *-mm.

    Your post actually reminds me that sched domain setup for exclusive
    cpusets are broken in the presence of cpu hotplug. That perhaps
    is a different context and will kick a different thread with interested
    parties.

    > In particular, I remain unsure of myself around the sched domain
    > code, and could use some feedback from someone with more of a
    > clue on whether I broke something here.

    I am not familiar with how job manager uses the cpusets but
    the current meaning/usage of 'cpu_exclusive' seems logical to me.

    Your current proposal seems to be wrong and broken.

    What your patch does is to have overlapping cpusets, lets take for
    example 2 cpusets and one cpuset with sched domain and another with
    no sched domain.

    All is fine(from cpu scheduler perspective) when the cpuset with
    sched domain is active and the job in cpuset with no sched domain is
    inactive. What happens when the job in the cpuset with no sched domain
    becomes active? In this case, scheduler can't make use of all cpus
    that this cpuset is allowed to use. This is because schedule domains in
    the system are paritioned based on the cpusets which define sched domain.

    cpus allowed for this cpuset(which doesnt define sched domain) may be spread
    across multiple sched domain partitions and scheduling doesn't happen across
    domain partitions.

    thanks,
    suresh
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