Re: [PATCH v5 22/29] x86,fs/resctrl: Handle domain creation/deletion for RDT_RESOURCE_PERF_PKG

[Fenghua Yu]

Hi, Tony,

On 5/21/25 15:50, Tony Luck wrote:
> The L3 resource has several requirements for domains. There are structures
> that hold the 64-bit values of counters, and elements to keep track of
> the overflow and limbo threads.
>
> None of these are needed for the PERF_PKG resource. The hardware counters
> are wide enough that they do not wrap around for decades.
>
> Define a new rdt_perf_pkg_mon_domain structure which just consists of
> the standard rdt_domain_hdr to keep track of domain id and CPU mask.
>
> Change domain_add_cpu_mon(), domain_remove_cpu_mon(),
> resctrl_offline_mon_domain(), and resctrl_online_mon_domain() to check
> resource type and perform only the operations needed for domains in the
> PERF_PKG resource.
>
> Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
> ---
>   arch/x86/kernel/cpu/resctrl/core.c | 41 ++++++++++++++++++++++++++++++
>   fs/resctrl/rdtgroup.c              |  4 +++
>   2 files changed, 45 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 64ce561e77a0..18d84c497ee4 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -540,6 +540,38 @@ static void l3_mon_domain_setup(int cpu, int id, struct rdt_resource *r, struct
>   	}
>   }
>   
> +/**
> + * struct rdt_perf_pkg_mon_domain - CPUs sharing an Intel-PMT-scoped resctrl monitor resource
> + * @hdr:	common header for different domain types
> + */
> +struct rdt_perf_pkg_mon_domain {
> +	struct rdt_domain_hdr   hdr;
> +};
> +
> +static void setup_intel_aet_mon_domain(int cpu, int id, struct rdt_resource *r,
> +				       struct list_head *add_pos)
> +{
> +	struct rdt_perf_pkg_mon_domain *d;
> +	int err;
> +
> +	d = kzalloc_node(sizeof(*d), GFP_KERNEL, cpu_to_node(cpu));
> +	if (!d)
> +		return;
> +
> +	d->hdr.id = id;
> +	d->hdr.type = RESCTRL_MON_DOMAIN;
> +	d->hdr.rid = r->rid;
> +	cpumask_set_cpu(cpu, &d->hdr.cpu_mask);
> +	list_add_tail_rcu(&d->hdr.list, add_pos);
> +
> +	err = resctrl_online_mon_domain(r, &d->hdr);
> +	if (err) {
> +		list_del_rcu(&d->hdr.list);
> +		synchronize_rcu();
> +		kfree(d);
> +	}
> +}
> +
>   static void domain_add_cpu_mon(int cpu, struct rdt_resource *r)
>   {
>   	int id = get_domain_id_from_scope(cpu, r->mon_scope);
> @@ -567,6 +599,9 @@ static void domain_add_cpu_mon(int cpu, struct rdt_resource *r)
>   	case RDT_RESOURCE_L3:
>   		l3_mon_domain_setup(cpu, id, r, add_pos);
>   		break;
> +	case RDT_RESOURCE_PERF_PKG:
> +		setup_intel_aet_mon_domain(cpu, id, r, add_pos);
> +		break;
>   	default:
>   		WARN_ON_ONCE(1);
>   	}
> @@ -666,6 +701,12 @@ static void domain_remove_cpu_mon(int cpu, struct rdt_resource *r)
>   	default:
>   		pr_warn_once("Unknown resource rid=%d\n", r->rid);
>   		break;
> +	case RDT_RESOURCE_PERF_PKG:
> +		resctrl_offline_mon_domain(r, hdr);
> +		list_del_rcu(&hdr->list);
> +		synchronize_rcu();
> +		kfree(container_of(hdr, struct rdt_perf_pkg_mon_domain, hdr));
> +		break;
>   	}

Why default is not the last one?

Thanks.

-Fenghua