Re: [PATCH v7 14/14] Documentation/filesystems/resctrl: Add footnote for telemetry fstab mount caveat

[Reinette Chatre]

Hi Tony,

On 6/1/26 12:56 PM, Tony Luck wrote:
> Add a footnote to the 'If telemetry monitoring is enabled' sentence noting
> that because PMT driver enumerates telemetry features asynchronously, an
> automatic mount of resctrl from /etc/fstab at boot may occur before those
> features are available, resulting in them not being enabled.
> 
> Assisted-by: Claude:Sonnet_4.6
> Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
> ---
>  Documentation/filesystems/resctrl.rst | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index b003bed339fd..4e62b8c5e0d6 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -620,7 +620,7 @@ When monitoring is enabled all MON groups will also contain:
>  	each instance of an L3 cache. Each directory contains files for the enabled
>  	L3 events (e.g. "llc_occupancy", "mbm_total_bytes", and "mbm_local_bytes").
>  
> -	If telemetry monitoring is enabled, there will be a "mon_PERF_PKG_YY"
> +	If telemetry monitoring is enabled [#]_, there will be a "mon_PERF_PKG_YY"
>  	directory for each physical processor package. Each directory contains
>  	files for the enabled telemetry events (e.g. "core_energy". "activity",
>  	"uops_retired", etc.)
> @@ -659,6 +659,11 @@ When monitoring is enabled all MON groups will also contain:
>  	returned if the MBM event does not have an assigned counter in the
>  	CTRL_MON group nor in any of its associated MON groups.
>  
> +.. [#] Telemetry features are enumerated asynchronously by the PMT driver. If
> +   resctrl is automatically mounted from ``/etc/fstab`` at boot, the telemetry
> +   features may not yet be available at mount time and will therefore not be
> +   enabled.

Would it be helpful to add a snippet that explains that in this scenario telemetry
features could be enabled on resctrl remount?

> +
>  "mon_hw_id":
>  	Available only with debug option. The identifier used by hardware
>  	for the monitor group. On x86 this is the RMID.

Reinette