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    SubjectRe: [PATCH] 2.5.21 Nonlinear CPU support
    Rusty Russell wrote:
    >
    > Linus, please apply. Tested on my dual x86 box.
    >
    > This patch removes smp_num_cpus, cpu_number_map and cpu_logical_map
    > from generic code, and uses cpu_online(cpu) instead, in preparation
    > for hotplug CPUS.

    umm. This patch does introduce a non-zero amount of bloat:

    > ...
    > - ntfs_compression_buffers = (u8**)kmalloc(smp_num_cpus * sizeof(u8*),
    > + ntfs_compression_buffers = (u8**)kmalloc(NR_CPUS * sizeof(u8*),

    and slowdown:

    > ...
    > --- linux-2.5.21.24110/kernel/sched.c Mon Jun 10 16:03:56 2002
    > +++ linux-2.5.21.24110.updated/kernel/sched.c Tue Jun 11 13:53:32 2002
    > ...
    > @@ -530,15 +530,16 @@
    >
    > busiest = NULL;
    > max_load = 1;
    > - for (i = 0; i < smp_num_cpus; i++) {
    > - int logical = cpu_logical_map(i);
    > + for (i = 0; i < NR_CPUS; i++) {
    > + if (!cpu_online(i))
    > + continue;
    >

    and for the majority of SMP machines it gives nothing back, yes?

    Is there some way of optimising all that?


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