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    SubjectRe: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19
    Andrew wrote:
    > > So I will leave that challenge on the table for someone else.
    > And I won't merge your patch ;)

    Be that way ;).

    > Seriously, it does appear that doing it per-task is adequate for your
    > needs, and it is certainly more general.

    My motivations for the per-cpuset, digitally filtered rate, as opposed
    to the per-task raw counter mostly have to do with minimizing total
    cost (user + kernel) of collecting this information. I have this phobia,
    perhaps not well founded, that moving critical scheduling/allocation
    decisions like this into user space will fail in some cases because
    the cost of gathering the critical information will be too intrusive
    on system performance and scalability.

    A per-task stat requires walking the tasklist, to build a list of the
    tasks to query.

    A raw counter requires repeated polling to determine the recent rate of

    The filtered per-cpuset rate avoids any need to repeatedly access
    global resources such as the tasklist, and minimizes the total cpu
    cycles required to get the interesting stat.

    > But I have to care for all users.

    Well you should, and well you do.

    If you have good reason, or just good instincts, to think that there
    are uses for per-task raw counters, then your choice is clear.

    As indeed it was clear.

    I don't recall hearing of any desire for per-task memory pressure data,
    until tonight.

    I will miss this patch. It had provided exactly what I thought was
    needed, with an extremely small impact on system (kern+user) performance.

    Oh well.

    I won't rest till it's the best ...
    Programmer, Linux Scalability
    Paul Jackson <> 1.925.600.0401
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