On Mon, May 27, 2013 at 07:09:00PM +0200, Andrew Jones wrote:
> Commit 316ad248307fb ("sched/x86: Rewrite set_cpu_sibling_map()") broke
> the construction of sibling maps, which also broke the booted_cores
> accounting.
>
> Before the rewrite, if smt was present, then each map was updated for
> each smt sibling. After the rewrite only cpu_sibling_mask gets updated,
> as the llc and core maps depend on 'has_mc = x86_max_cores > 1' instead.
> This leads to problems with topologies like the following
>
> (qemu -smp sockets=2,cores=1,threads=2)
>
> processor : 0
> physical id : 0
> siblings : 1 <= should be 2
> core id : 0
> cpu cores : 1
>
> processor : 1
> physical id : 0
> siblings : 1 <= should be 2
> core id : 0
> cpu cores : 0 <= should be 1
>
> processor : 2
> physical id : 1
> siblings : 1 <= should be 2
> core id : 0
> cpu cores : 1
>
> processor : 3
> physical id : 1
> siblings : 1 <= should be 2
> core id : 0
> cpu cores : 0 <= should be 1
>
> This patch restores the former construction by defining has_mc as
> (has_smt || x86_max_cores > 1). This should be fine as there were no
> (has_smt && !has_mc) conditions in the context.
>
> Signed-off-by: Andrew Jones <drjo...@redhat.com>
> ---
> arch/x86/kernel/smpboot.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 9c73b51817e47..886a3234eaff3 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -372,15 +372,15 @@ static bool __cpuinit match_mc(struct cpuinfo_x86 *c,
> struct cpuinfo_x86 *o)
>
> void __cpuinit set_cpu_sibling_map(int cpu)
> {
> - bool has_mc = boot_cpu_data.x86_max_cores > 1;
> bool has_smt = smp_num_siblings > 1;
> + bool has_mc = has_smt || boot_cpu_data.x86_max_cores > 1;
> struct cpuinfo_x86 *c = &cpu_data(cpu);
> struct cpuinfo_x86 *o;
> int i;
>
> cpumask_set_cpu(cpu, cpu_sibling_setup_mask);
>
> - if (!has_smt && !has_mc) {
> + if (!has_mc) {
> cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
> cpumask_set_cpu(cpu, cpu_llc_shared_mask(cpu));
> cpumask_set_cpu(cpu, cpu_core_mask(cpu));
> --
> 1.8.1.4
>
Any acks? This patch fixes a regression. Also, in case anybody is
wondering, this is not the same regression as was already fixed with
ceb1cbac8eda6 sched/x86: Calculate booted cores after construction of
sibling_mask
(Hmm, I probably should have renamed has_mc to has_mp, as the redefinition
expands its scope. I'm not sure if that deserves a v2 though.)
drew
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
