linux-kernel - Re: [PATCH v8 07/13] x86/resctrl: Introduce data structure to support monitor configuration

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Message-ID: <74fc09e7-3a75-2c62-d505-244a12b6190f@intel.com>
Date:   Tue, 22 Nov 2022 16:14:45 -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>
Subject: Re: [PATCH v8 07/13] x86/resctrl: Introduce data structure to support
 monitor configuration

Hi Babu,

On 11/4/2022 1:00 PM, Babu Moger wrote:
> Add a new field in mon_evt to support Bandwidth Monitoring Event
> Configuration(BMEC) and also update the "mon_features" display.
> 
> The sysfs file "mon_features" will display the monitor configuration

sysfs -> resctrl ?

> if supported.

This is not clear. "mon_features" does not display the monitor
configuration, it displays the name of the file that can be used to 
see the monitor configuration.

> 
> Before the change.
> 	$cat /sys/fs/resctrl/info/L3_MON/mon_features
> 	llc_occupancy
> 	mbm_total_bytes
> 	mbm_local_bytes
> 
> After the change when BMEC is supported.
> 	$cat /sys/fs/resctrl/info/L3_MON/mon_features
> 	llc_occupancy
> 	mbm_total_bytes
> 	mbm_total_bytes_config
> 	mbm_local_bytes
> 	mbm_local_bytes_config
> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
>  arch/x86/kernel/cpu/resctrl/internal.h |    2 ++
>  arch/x86/kernel/cpu/resctrl/monitor.c  |    6 ++++++
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c |    5 ++++-
>  3 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index e30e8b23f6b5..5459b5022760 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -63,11 +63,13 @@ DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
>   * struct mon_evt - Entry in the event list of a resource
>   * @evtid:		event id
>   * @name:		name of the event
> + * @configurable:	true if the event is configurable
>   * @list:		entry in &rdt_resource->evt_list
>   */
>  struct mon_evt {
>  	enum resctrl_event_id	evtid;
>  	char			*name;
> +	bool			configurable;
>  	struct list_head	list;
>  };
>  
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index efe0c30d3a12..06c2dc980855 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -750,6 +750,7 @@ int rdt_get_mon_l3_config(struct rdt_resource *r)
>  {
>  	unsigned int mbm_offset = boot_cpu_data.x86_cache_mbm_width_offset;
>  	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> +	bool mon_configurable = rdt_cpu_has(X86_FEATURE_BMEC);
>  	unsigned int threshold;
>  	int ret;
>  
> @@ -783,6 +784,11 @@ int rdt_get_mon_l3_config(struct rdt_resource *r)
>  	if (ret)
>  		return ret;
>  
> +	if (mon_configurable) {
> +		mbm_total_event.configurable = true;
> +		mbm_local_event.configurable = true;
> +	}
> +

Is the local variable needed? Why not just:
	if (rdt_cpu_has(X86_FEATURE_BMEC))


Reinette