[PATCH 05/11] powerpc/smp: Dont assume l2-cache to be superset of sibling
Oliver O'Halloran
oohall at gmail.com
Tue Jul 14 15:40:09 AEST 2020
On Tue, Jul 14, 2020 at 2:45 PM Srikar Dronamraju
<srikar at linux.vnet.ibm.com> wrote:
>
> Current code assumes that cpumask of cpus sharing a l2-cache mask will
> always be a superset of cpu_sibling_mask.
>
> Lets stop that assumption.
It's been a while since I looked, but I'm pretty sure the scheduler
requires child domains to be subsets of their parents. Why is this
necessary or a good idea?
> Cc: linuxppc-dev <linuxppc-dev at lists.ozlabs.org>
> Cc: Michael Ellerman <michaele at au1.ibm.com>
> Cc: Nick Piggin <npiggin at au1.ibm.com>
> Cc: Oliver OHalloran <oliveroh at au1.ibm.com>
> Cc: Nathan Lynch <nathanl at linux.ibm.com>
> Cc: Michael Neuling <mikey at linux.ibm.com>
> Cc: Anton Blanchard <anton at au1.ibm.com>
> Cc: Gautham R Shenoy <ego at linux.vnet.ibm.com>
> Cc: Vaidyanathan Srinivasan <svaidy at linux.ibm.com>
> Signed-off-by: Srikar Dronamraju <srikar at linux.vnet.ibm.com>
> ---
> arch/powerpc/kernel/smp.c | 28 +++++++++++++++-------------
> 1 file changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 7d430fc536cc..875f57e41355 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -1198,6 +1198,7 @@ static bool update_mask_by_l2(int cpu, struct cpumask *(*mask_fn)(int))
> struct device_node *l2_cache, *np;
> int i;
>
> + cpumask_set_cpu(cpu, mask_fn(cpu));
?
> l2_cache = cpu_to_l2cache(cpu);
> if (!l2_cache)
> return false;
> @@ -1284,29 +1285,30 @@ static void add_cpu_to_masks(int cpu)
> * add it to it's own thread sibling mask.
> */
> cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
> + cpumask_set_cpu(cpu, cpu_core_mask(cpu));
>
> for (i = first_thread; i < first_thread + threads_per_core; i++)
> if (cpu_online(i))
> set_cpus_related(i, cpu, cpu_sibling_mask);
>
> add_cpu_to_smallcore_masks(cpu);
> - /*
> - * Copy the thread sibling mask into the cache sibling mask
> - * and mark any CPUs that share an L2 with this CPU.
> - */
> - for_each_cpu(i, cpu_sibling_mask(cpu))
> - set_cpus_related(cpu, i, cpu_l2_cache_mask);
> update_mask_by_l2(cpu, cpu_l2_cache_mask);
>
> - /*
> - * Copy the cache sibling mask into core sibling mask and mark
> - * any CPUs on the same chip as this CPU.
> - */
> - for_each_cpu(i, cpu_l2_cache_mask(cpu))
> - set_cpus_related(cpu, i, cpu_core_mask);
> + if (pkg_id == -1) {
> + struct cpumask *(*mask)(int) = cpu_sibling_mask;
> +
> + /*
> + * Copy the sibling mask into core sibling mask and
> + * mark any CPUs on the same chip as this CPU.
> + */
> + if (shared_caches)
> + mask = cpu_l2_cache_mask;
> +
> + for_each_cpu(i, mask(cpu))
> + set_cpus_related(cpu, i, cpu_core_mask);
>
> - if (pkg_id == -1)
> return;
> + }
>
> for_each_cpu(i, cpu_online_mask)
> if (get_physical_package_id(i) == pkg_id)
> --
> 2.17.1
>
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