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    SubjectRe: [PATCH 0/1] x86: Convert cpuinfo_x86 array to a per_cpu array v3
    On Tue, 16 Oct 2007, Andrew Morton wrote:

    > On Mon, 24 Sep 2007 14:08:53 -0700 wrote:

    > > cpu_sibling_map and cpu_core_map have been taken care of in
    > > a prior patch. This patch deals with the cpu_data array of
    > > cpuinfo_x86 structs. The model that was used in sparc64
    > > architecture was adopted for x86.
    > This has mysteriously started to oops on me, only on x86_64.
    > which is a bit strange since this patch doesn't touch sched.c. Maybe
    > there's something somewhere else in the -mm lineup which when combined with
    > this prevents it from oopsing, dunno. I'll hold it back for now and will
    > see what happens.

    The config that you are using has





    So we use cpu_corecroup_map() from arch/x86_64/kernel/smpboot.c in
    cpu_to_phys_group that has these nice convoluted ifdefs:

    static int cpu_to_phys_group(int cpu, const cpumask_t *cpu_map,
    struct sched_group **sg)
    int group;
    #ifdef CONFIG_SCHED_MC
    cpumask_t mask = cpu_coregroup_map(cpu);
    cpus_and(mask, mask, *cpu_map);
    group = first_cpu(mask);
    #elif defined(CONFIG_SCHED_SMT)
    cpumask_t mask = per_cpu(cpu_sibling_map, cpu);
    cpus_and(mask, mask, *cpu_map);
    group = first_cpu(mask);
    group = cpu;
    if (sg)
    *sg = &per_cpu(sched_group_phys, group);
    return group;

    and I guess that some sched domain patches resulted in an empty
    nodemask so that we end up with an invalid group number for the sched

    /* maps the cpu to the sched domain representing multi-core */
    cpumask_t cpu_coregroup_map(int cpu)
    struct cpuinfo_x86 *c = &cpu_data(cpu);
    * For perf, we return last level cache shared map.
    * And for power savings, we return cpu_core_map
    if (sched_mc_power_savings || sched_smt_power_savings)
    return per_cpu(cpu_core_map, cpu);
    return c->llc_shared_map;

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      Last update: 2007-10-16 17:05    [W:0.048 / U:0.668 seconds]
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