linux-kernel - Re: [PATCH v9 12/13] x86/resctrl: Replace smp_call_function_many() with on_each_cpu

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Message-ID: <27680a78-d9c1-b86b-8aa4-38245d0547d7@intel.com>
Date:   Thu, 15 Dec 2022 10:26:38 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Babu Moger <babu.moger@....com>, <corbet@....net>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>
CC:     <fenghua.yu@...el.com>, <dave.hansen@...ux.intel.com>,
        <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
        <akpm@...ux-foundation.org>, <quic_neeraju@...cinc.com>,
        <rdunlap@...radead.org>, <damien.lemoal@...nsource.wdc.com>,
        <songmuchun@...edance.com>, <peterz@...radead.org>,
        <jpoimboe@...nel.org>, <pbonzini@...hat.com>,
        <chang.seok.bae@...el.com>, <pawan.kumar.gupta@...ux.intel.com>,
        <jmattson@...gle.com>, <daniel.sneddon@...ux.intel.com>,
        <sandipan.das@....com>, <tony.luck@...el.com>,
        <james.morse@....com>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <bagasdotme@...il.com>,
        <eranian@...gle.com>, <christophe.leroy@...roup.eu>,
        <jarkko@...nel.org>, <adrian.hunter@...el.com>,
        <quic_jiles@...cinc.com>, <peternewman@...gle.com>
Subject: Re: [PATCH v9 12/13] x86/resctrl: Replace smp_call_function_many()
 with on_each_cpu_mask()

Hi Babu,

On 12/1/2022 7:37 AM, Babu Moger wrote:
> The call on_each_cpu_mask() runs the function on each CPU specified
> by cpumask, which may include the local processor. So, replace the call
> smp_call_function_many() with on_each_cpu_mask() to simplify the code.

Please move the solution to a new paragraph and drop the "So,". The two
instances of "the call" can be dropped also.

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

Could you please move this patch to the beginning of this series?
Fixes and cleanups should go before new features.

>  arch/x86/kernel/cpu/resctrl/rdtgroup.c |   29 ++++++++---------------------
>  1 file changed, 8 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 6897c480ae55..68e14831a638 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -325,12 +325,7 @@ static void update_cpu_closid_rmid(void *info)
>  static void
>  update_closid_rmid(const struct cpumask *cpu_mask, struct rdtgroup *r)
>  {
> -	int cpu = get_cpu();
> -
> -	if (cpumask_test_cpu(cpu, cpu_mask))
> -		update_cpu_closid_rmid(r);
> -	smp_call_function_many(cpu_mask, update_cpu_closid_rmid, r, 1);
> -	put_cpu();
> +	on_each_cpu_mask(cpu_mask, update_cpu_closid_rmid, r, 1);
>  }
>  
>  static int cpus_mon_write(struct rdtgroup *rdtgrp, cpumask_var_t newmask,
> @@ -2135,13 +2130,9 @@ static int set_cache_qos_cfg(int level, bool enable)
>  			/* Pick one CPU from each domain instance to update MSR */
>  			cpumask_set_cpu(cpumask_any(&d->cpu_mask), cpu_mask);
>  	}
> -	cpu = get_cpu();
> -	/* Update QOS_CFG MSR on this cpu if it's in cpu_mask. */
> -	if (cpumask_test_cpu(cpu, cpu_mask))
> -		update(&enable);
> -	/* Update QOS_CFG MSR on all other cpus in cpu_mask. */
> -	smp_call_function_many(cpu_mask, update, &enable, 1);
> -	put_cpu();
> +
> +	/* Update QOS_CFG MSR on all the CPUs in cpu_mask */
> +	on_each_cpu_mask(cpu_mask, update, &enable, 1);
>  
>  	free_cpumask_var(cpu_mask);
>  
> @@ -2618,7 +2609,7 @@ static int reset_all_ctrls(struct rdt_resource *r)
>  	struct msr_param msr_param;
>  	cpumask_var_t cpu_mask;
>  	struct rdt_domain *d;
> -	int i, cpu;
> +	int i;
>  
>  	if (!zalloc_cpumask_var(&cpu_mask, GFP_KERNEL))
>  		return -ENOMEM;
> @@ -2639,13 +2630,9 @@ static int reset_all_ctrls(struct rdt_resource *r)
>  		for (i = 0; i < hw_res->num_closid; i++)
>  			hw_dom->ctrl_val[i] = r->default_ctrl;
>  	}
> -	cpu = get_cpu();
> -	/* Update CBM on this cpu if it's in cpu_mask. */
> -	if (cpumask_test_cpu(cpu, cpu_mask))
> -		rdt_ctrl_update(&msr_param);
> -	/* Update CBM on all other cpus in cpu_mask. */
> -	smp_call_function_many(cpu_mask, rdt_ctrl_update, &msr_param, 1);
> -	put_cpu();
> +
> +	/* Update CBM on all the CPUs in cpu_mask */
> +	on_each_cpu_mask(cpu_mask, rdt_ctrl_update, &msr_param, 1);
>  
>  	free_cpumask_var(cpu_mask);
>  
> 
> 

Should the snippet in resctrl_arch_update_domains() also be updated?

Reinette