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    SubjectRe: latest linus-2.5 BK broken
    In message <> you write:
    > On Wed, Jun 19, 2002 at 04:51:31AM +1000, Rusty Russell wrote:
    > > You could do a loop here, but the real problem is the broken userspace
    > > interface. Can you fix this so it takes a single CPU number please?
    > >
    > > ie.
    > > /* -1 = remove affinity */
    > > sys_sched_setaffinity(pid_t pid, int cpu);
    > >
    > > This will work everywhere, and doesn't require userspace to know the
    > > size of the cpu bitmask etc.
    > That doesn't work. Think of SMT CPU pairs (aka HyperThreading) or
    > quads that share caches.

    This is the NUMA "I want to be in this group" problem. If you're
    serious about this, you'll go for a sys_sched_groupaffinity call, or
    add an extra arg to sys_sched_setaffinity, or simply use the top 16
    bits of the cpu arg.

    You will also add /proc/cpugroups or something to export this
    information to users so there's a point.

    Sorry, the current interface is insufficient for NUMA *and* is
    impossible[1] for the user to use correctly.

    [1] Defined as "too hard for them to ever do it properly"
    Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
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