linux-kernel - Re: [PATCH v10 09/24] x86/resctrl: Introduce interface to display number of monitoring counters

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Message-ID: <a1672556-5771-493c-930f-749d721b73df@intel.com>
Date: Thu, 19 Dec 2024 14:03:37 -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>, <dave.hansen@...ux.intel.com>,
	<tony.luck@...el.com>, <peternewman@...gle.com>
CC: <fenghua.yu@...el.com>, <x86@...nel.org>, <hpa@...or.com>,
	<paulmck@...nel.org>, <akpm@...ux-foundation.org>, <thuth@...hat.com>,
	<rostedt@...dmis.org>, <xiongwei.song@...driver.com>,
	<pawan.kumar.gupta@...ux.intel.com>, <daniel.sneddon@...ux.intel.com>,
	<jpoimboe@...nel.org>, <perry.yuan@....com>, <andipan.das@....com>,
	<kai.huang@...el.com>, <xiaoyao.li@...el.com>, <seanjc@...gle.com>,
	<xin3.li@...el.com>, <andrew.cooper3@...rix.com>, <ebiggers@...gle.com>,
	<mario.limonciello@....com>, <james.morse@....com>,
	<tan.shaopeng@...itsu.com>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <maciej.wieczor-retman@...el.com>,
	<eranian@...gle.com>
Subject: Re: [PATCH v10 09/24] x86/resctrl: Introduce interface to display
 number of monitoring counters

Hi Babu,

On 12/12/24 12:15 PM, Babu Moger wrote:
> The mbm_cntr_assign mode provides an option to the user to assign a
> counter to an RMID, event pair and monitor the bandwidth as long as
> the counter is assigned. Number of assignments depend on number of
> monitoring counters available.
> 
> Provide the interface to display the number of monitoring counters
> supported. The interface file 'num_mbm_cntrs' is available when an
> architecture supports mbm_cntr_assign mode.

How about: "The resctrl file 'num_mbm_cntrs' is visible to user space
when the system supports mbm_cntr_assign mode." ?

> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
> v10: No changes.
> 
> v9: Updated user document based on the comments.
>     Will add a new file available_mbm_cntrs later in the series.
> 
> v8: Commit message update and documentation update.
> 
> v7: Minor commit log text changes.
> 
> v6: No changes.
> 
> v5: Changed the display name from num_cntrs to num_mbm_cntrs.
>     Updated the commit message.
>     Moved the patch after mbm_mode is introduced.
> 
> v4: Changed the counter name to num_cntrs. And few text changes.
> 
> v3: Changed the field name to mbm_assign_cntrs.
> 
> v2: Changed the field name to mbm_assignable_counters from abmc_counter.
> ---
> ---
>  Documentation/arch/x86/resctrl.rst     | 12 ++++++++++++
>  arch/x86/kernel/cpu/resctrl/monitor.c  |  1 +
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 16 ++++++++++++++++
>  3 files changed, 29 insertions(+)
> 
> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
> index 1e4a1f615496..43a861adeada 100644
> --- a/Documentation/arch/x86/resctrl.rst
> +++ b/Documentation/arch/x86/resctrl.rst
> @@ -290,6 +290,18 @@ with the following files:
>  	"mbm_total_bytes" or "mbm_local_bytes" will report 'Unavailable' if
>  	there is no counter associated with that event.
>  
> +"num_mbm_cntrs":
> +	The number of monitoring counters available for assignment when the
> +	architecture supports mbm_cntr_assign mode.

"architecture supports" -> "system supports"

> +
> +	The resctrl file system supports tracking up to two memory bandwidth
> +	events per monitoring group: mbm_total_bytes and/or mbm_local_bytes.
> +	Up to two counters can be assigned per monitoring group, one for each
> +	memory bandwidth event. More monitoring groups can be tracked by
> +	assigning one counter per monitoring group. However, doing so limits
> +	memory bandwidth tracking to a single memory bandwidth event per
> +	monitoring group.
> +
>  "max_threshold_occupancy":
>  		Read/write file provides the largest value (in
>  		bytes) at which a previously used LLC_occupancy
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 80be91671dc1..c23e94fa6852 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -1237,6 +1237,7 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
>  			r->mon.mbm_cntr_assignable = true;
>  			cpuid_count(0x80000020, 5, &eax, &ebx, &ecx, &edx);
>  			r->mon.num_mbm_cntrs = (ebx & GENMASK(15, 0)) + 1;
> +			resctrl_file_fflags_init("num_mbm_cntrs", RFTYPE_MON_INFO);
>  		}
>  	}
>  
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index f25ff1430014..339bb0b09a82 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -869,6 +869,16 @@ static int rdtgroup_mbm_assign_mode_show(struct kernfs_open_file *of,
>  	return 0;
>  }
>  
> +static int rdtgroup_num_mbm_cntrs_show(struct kernfs_open_file *of,
> +				       struct seq_file *s, void *v)

No rdtgroup_ namespace, this can be resctrl_

> +{
> +	struct rdt_resource *r = of->kn->parent->priv;
> +
> +	seq_printf(s, "%d\n", r->mon.num_mbm_cntrs);
> +
> +	return 0;
> +}
> +
>  #ifdef CONFIG_PROC_CPU_RESCTRL
>  
>  /*

Reinette