Re: [PATCH v3 10/16] arch_topology: Set thread sibling cpumask only within the cluster

Gavin Shan
2022-06-01T03:38:57Z

On 5/25/22 4:14 PM, Sudeep Holla wrote:
> Currently the cluster identifier is not set on the DT based platforms.
> The reset or default value is -1 for all the CPUs. Once we assign the
> cluster identifier values correctly that imay result in getting the thread
> siblings wrongs as the core identifiers can be same for 2 different CPUs
> belonging to 2 different cluster.
>
> So, in order to get the thread sibling cpumasks correct, we need to
> update them only if the cores they belong are in the same cluster within
> the socket. Let us skip updation of the thread sibling cpumaks if the
> cluster identifier doesn't match.
>
> This change won't affect even if the cluster identifiers are not set
> currently but will avoid any breakage once we set the same correctly.
>
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
> drivers/base/arch_topology.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>

Reviewed-by: Gavin Shan <gshan@redhat.com>
Tested-by: Gavin Shan <gshan@redhat.com>

> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 76c702c217c5..59dc2c80c439 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -703,15 +703,17 @@ void update_siblings_masks(unsigned int cpuid)
> if (cpuid_topo->package_id != cpu_topo->package_id)
> continue;
>
> - if (cpuid_topo->cluster_id == cpu_topo->cluster_id &&
> - cpuid_topo->cluster_id != -1) {
> + cpumask_set_cpu(cpuid, &cpu_topo->core_sibling);
> + cpumask_set_cpu(cpu, &cpuid_topo->core_sibling);
> +
> + if (cpuid_topo->cluster_id != cpu_topo->cluster_id)
> + continue;
> +
> + if (cpuid_topo->cluster_id != -1) {
> cpumask_set_cpu(cpu, &cpuid_topo->cluster_sibling);
> cpumask_set_cpu(cpuid, &cpu_topo->cluster_sibling);
> }
>
> - cpumask_set_cpu(cpuid, &cpu_topo->core_sibling);
> - cpumask_set_cpu(cpu, &cpuid_topo->core_sibling);
> -
> if (cpuid_topo->core_id != cpu_topo->core_id)
> continue;