Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 9 Jan 2023 23:26:56 +0000
From:   Ashok Raj <ashok_raj@linux.intel.com>
To:     Babu Moger <babu.moger@amd.com>
Cc:     corbet@lwn.net, reinette.chatre@intel.com, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, fenghua.yu@intel.com,
        dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
        paulmck@kernel.org, akpm@linux-foundation.org,
        quic_neeraju@quicinc.com, rdunlap@infradead.org,
        damien.lemoal@opensource.wdc.com, songmuchun@bytedance.com,
        peterz@infradead.org, jpoimboe@kernel.org, pbonzini@redhat.com,
        chang.seok.bae@intel.com, pawan.kumar.gupta@linux.intel.com,
        jmattson@google.com, daniel.sneddon@linux.intel.com,
        sandipan.das@amd.com, tony.luck@intel.com, james.morse@arm.com,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        bagasdotme@gmail.com, eranian@google.com,
        christophe.leroy@csgroup.eu, jarkko@kernel.org,
        adrian.hunter@intel.com, quic_jiles@quicinc.com,
        peternewman@google.com, Ashok Raj <ashok.raj@intel.com>
Subject: Re: [PATCH v11 01/13] x86/resctrl: Replace smp_call_function_many()
 with on_each_cpu_mask()
Message-ID: <Y7yiwOerGiEKAF9i@araj-dh-work>
References: <20230109164405.569714-1-babu.moger@amd.com>
 <20230109164405.569714-2-babu.moger@amd.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20230109164405.569714-2-babu.moger@amd.com>
Precedence: bulk

On Mon, Jan 09, 2023 at 10:43:53AM -0600, Babu Moger wrote:
> on_each_cpu_mask() runs the function on each CPU specified by cpumask,
> which may include the local processor.
> 
> Replace smp_call_function_many() with on_each_cpu_mask() to simplify
> the code.
> 
> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
>  arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 11 +++------
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c    | 29 +++++++----------------
>  2 files changed, 11 insertions(+), 29 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> index 1df0e3262bca..7eece3d2d0c3 100644
> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> @@ -310,7 +310,6 @@ int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid)
>  	enum resctrl_conf_type t;
>  	cpumask_var_t cpu_mask;
>  	struct rdt_domain *d;
> -	int cpu;
>  	u32 idx;
>  
>  	if (!zalloc_cpumask_var(&cpu_mask, GFP_KERNEL))
> @@ -341,13 +340,9 @@ int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid)
>  
>  	if (cpumask_empty(cpu_mask))
>  		goto done;
> -	cpu = get_cpu();
> -	/* Update resource control msr on this CPU if it's in cpu_mask. */
> -	if (cpumask_test_cpu(cpu, cpu_mask))
> -		rdt_ctrl_update(&msr_param);
> -	/* Update resource control msr on other CPUs. */
> -	smp_call_function_many(cpu_mask, rdt_ctrl_update, &msr_param, 1);
> -	put_cpu();
> +
> +	/* Update resource control msr on all the CPUs. */
> +	on_each_cpu_mask(cpu_mask, rdt_ctrl_update, &msr_param, 1);

Do you require these updates to done immediately via an IPI? or can they be
done bit lazy via schedule_on_each_cpu()? 

Cheers,
Ashok