linux-kernel - Re: [PATCH v15 32/32] x86,fs/resctrl: Update documentation for telemetry events

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Message-ID: <e0c88658-6724-4307-8719-d94d2b65dd3a@intel.com>
Date: Tue, 9 Dec 2025 11:43:31 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghuay@...dia.com>, "Maciej
 Wieczor-Retman" <maciej.wieczor-retman@...el.com>, Peter Newman
	<peternewman@...gle.com>, James Morse <james.morse@....com>, Babu Moger
	<babu.moger@....com>, Drew Fustini <dfustini@...libre.com>, Dave Martin
	<Dave.Martin@....com>, Chen Yu <yu.c.chen@...el.com>
CC: <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<patches@...ts.linux.dev>
Subject: Re: [PATCH v15 32/32] x86,fs/resctrl: Update documentation for
 telemetry events

Hi Tony,

On 12/4/25 12:54 PM, Tony Luck wrote:
> Update resctrl filesystem documentation with the details about the
> resctrl files that support telemetry events.
> 
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> ---
>  Documentation/filesystems/resctrl.rst | 102 +++++++++++++++++++++++---
>  1 file changed, 90 insertions(+), 12 deletions(-)
> 
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index 8c8ce678148a..5418ca72bed3 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -252,13 +252,12 @@ with respect to allocation:
>  			bandwidth percentages are directly applied to
>  			the threads running on the core
>  
> -If RDT monitoring is available there will be an "L3_MON" directory
> +If L3 monitoring is available there will be an "L3_MON" directory
>  with the following files:
>  
>  "num_rmids":
> -		The number of RMIDs available. This is the
> -		upper bound for how many "CTRL_MON" + "MON"
> -		groups can be created.
> +		The number of RMIDs supported by hardware for
> +		L3 monitoring events.
>  
>  "mon_features":
>  		Lists the monitoring events if
> @@ -484,6 +483,25 @@ with the following files:
>  		bytes) at which a previously used LLC_occupancy
>  		counter can be considered for re-use.
>  
> +If telemetry monitoring is available there will be a "PERF_PKG_MON" directory
> +with the following files:
> +
> +"num_rmids":
> +		The number of RMIDs for telemetry monitoring events. By default,
> +		resctrl will not enable telemetry events of a particular type
> +		("perf" or "energy") if the number of RMIDs that can be tracked
> +		concurrently for that type is lower than the total number of
> +		RMIDs supported by that type. The user can force-enable each
> +		type (or individual guids within a type) of telemetry events
> +		with the "rdt=" boot command line option, but this may reduce
> +		the number of monitoring groups that can be created.

Same comment as before. To make this easier to handle I suggest this is split into
resctrl fs and arch parts. Consider, for example:

  "num_rmids":
		The number of RMIDs for telemetry monitoring events.
		
		On Intel resctrl will not enable telemetry events if the number of
		RMIDs that can be tracked concurrently is lower than the total number
		of RMIDs supported. Telemetry events can be force-enabled with the
		"rdt=" kernel parameter, but this may reduce the number of
		monitoring groups that can be created.


Reinette