linux-kernel - Re: [PATCH v4 12/20] arch_topology: Set thread sibling cpumask only within the cluster

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Message-ID: <Yrmz0ZAUaFCqMt5u@arm.com>
Date:   Mon, 27 Jun 2022 14:42:41 +0100
From:   Ionela Voinescu <ionela.voinescu@....com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     linux-kernel@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
        Atish Patra <atishp@...shpatra.org>,
        Atish Patra <atishp@...osinc.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Qing Wang <wangqing@...o.com>,
        Rob Herring <robh+dt@...nel.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Pierre Gondois <pierre.gondois@....com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, Gavin Shan <gshan@...hat.com>
Subject: Re: [PATCH v4 12/20] arch_topology: Set thread sibling cpumask only
 within the cluster

On Tuesday 21 Jun 2022 at 20:20:26 (+0100), 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
                                           ^^^^
Nit: 					   may
> siblings wrongs as the core identifiers can be same for 2 different CPUs
Nit:       ^^^^^^
	   wrong


Thanks,
Ionela.

> 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.
> 
> Reviewed-by: Gavin Shan <gshan@...hat.com>
> Tested-by: Gavin Shan <gshan@...hat.com>
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> ---
>  drivers/base/arch_topology.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index b63cc52e12ce..7a5ff1ea5f00 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -708,15 +708,17 @@ 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;
>  
> -- 
> 2.36.1
>