linux-kernel - Re: [PATCH v7 23/24] x86/resctrl: Move domain helper migration into resctrl_offline

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Message-ID: <7b962474-fea4-4947-8241-b46aa3b09bf2@amd.com>
Date:   Thu, 9 Nov 2023 14:52:15 -0600
From:   "Moger, Babu" <babu.moger@....com>
To:     James Morse <james.morse@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        shameerali.kolothum.thodi@...wei.com,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        carl@...amperecomputing.com, lcherian@...vell.com,
        bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
        baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
        dfustini@...libre.com, amitsinght@...vell.com
Subject: Re: [PATCH v7 23/24] x86/resctrl: Move domain helper migration into
 resctrl_offline_cpu()



On 10/25/23 13:03, James Morse wrote:
> When a CPU is taken offline the resctrl filesystem code needs to check
> if it was the CPU nominated to perform the periodic overflow and limbo
> work. If so, another CPU needs to be chosen to do this work.
> 
> This is currently done in core.c, mixed in with the code that removes
> the CPU from the domain's mask, and potentially free()s the domain.
> 
> Move the migration of the overflow and limbo helpers into the filesystem
> code, into resctrl_offline_cpu(). As resctrl_offline_cpu() runs before
> the architecture code has removed the CPU from the domain mask, the
> callers need to be told which CPU is being removed, to avoid picking
> it as the new CPU. This uses the exclude_cpu feature previously
> added.
> 
> Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Tested-by: Peter Newman <peternewman@...gle.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> Signed-off-by: James Morse <james.morse@....com>

Reviewed-by: Babu Moger <babu.moger@....com>

> ---
> Changes since v5:
>  * Changed fir tree order of variables.
>  * Added mon-capable check for cpu offline.
> 
> No changes since v6
> ---
>  arch/x86/kernel/cpu/resctrl/core.c     | 16 ----------------
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 18 ++++++++++++++++++
>  2 files changed, 18 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 7d09b8d7c653..a90a07a5c876 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -582,22 +582,6 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)
>  
>  		return;
>  	}
> -
> -	if (r == &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl) {
> -		if (is_mbm_enabled() && cpu == d->mbm_work_cpu) {
> -			cancel_delayed_work(&d->mbm_over);
> -			/*
> -			 * temporary: exclude_cpu=-1 as this CPU has already
> -			 * been removed by cpumask_clear_cpu()d
> -			 */
> -			mbm_setup_overflow_handler(d, 0, RESCTRL_PICK_ANY_CPU);
> -		}
> -		if (is_llc_occupancy_enabled() && cpu == d->cqm_work_cpu &&
> -		    has_busy_rmid(d)) {
> -			cancel_delayed_work(&d->cqm_limbo);
> -			cqm_setup_limbo_handler(d, 0, RESCTRL_PICK_ANY_CPU);
> -		}
> -	}
>  }
>  
>  static void clear_closid_rmid(int cpu)
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 971a8397e243..d38b2fe6e3ca 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -4034,7 +4034,9 @@ static void clear_childcpus(struct rdtgroup *r, unsigned int cpu)
>  
>  void resctrl_offline_cpu(unsigned int cpu)
>  {
> +	struct rdt_resource *l3 = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
>  	struct rdtgroup *rdtgrp;
> +	struct rdt_domain *d;
>  
>  	lockdep_assert_held(&rdtgroup_mutex);
>  
> @@ -4044,6 +4046,22 @@ void resctrl_offline_cpu(unsigned int cpu)
>  			break;
>  		}
>  	}
> +
> +	if (!l3->mon_capable)
> +		return;
> +
> +	d = get_domain_from_cpu(cpu, l3);
> +	if (d) {
> +		if (is_mbm_enabled() && cpu == d->mbm_work_cpu) {
> +			cancel_delayed_work(&d->mbm_over);
> +			mbm_setup_overflow_handler(d, 0, cpu);
> +		}
> +		if (is_llc_occupancy_enabled() && cpu == d->cqm_work_cpu &&
> +		    has_busy_rmid(d)) {
> +			cancel_delayed_work(&d->cqm_limbo);
> +			cqm_setup_limbo_handler(d, 0, cpu);
> +		}
> +	}
>  }
>  
>  /*

-- 
Thanks
Babu Moger