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

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Date:   Wed, 1 Jun 2022 11:36:44 +0800
From:   Gavin Shan <gshan@...hat.com>
To:     Sudeep Holla <sudeep.holla@....com>, linux-kernel@...r.kernel.org
Cc:     Atish Patra <atishp@...shpatra.org>,
        Atish Patra <atishp@...osinc.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Qing Wang <wangqing@...o.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v3 10/16] arch_topology: Set thread sibling cpumask only
 within the cluster

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@....com>
> ---
>   drivers/base/arch_topology.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
> 

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