linux-kernel - Re: [PATCH v11 08/23] x86/resctrl: Introduce interface to display number of monitoring counters

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Message-ID: <6376ea35-4ce7-4ac1-967b-97f2728228e3@intel.com>
Date: Wed, 5 Feb 2025 15:17:28 -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: <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>, <sandipan.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 v11 08/23] x86/resctrl: Introduce interface to display
 number of monitoring counters

Hi Babu,

On 1/22/25 12:20 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 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>
> ---

...

> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
> index b5defc5bce0e..31ff764deeeb 100644
> --- a/Documentation/arch/x86/resctrl.rst
> +++ b/Documentation/arch/x86/resctrl.rst
> @@ -283,6 +283,22 @@ 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
> +	system supports mbm_cntr_assign mode.
> +	::
> +
> +	  # cat /sys/fs/resctrl/info/L3_MON/num_mbm_cntrs
> +	  32
> +
> +	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.
> +

This text needs an update to reflect the switch to per-domain counter assignment.

Reinette