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

[Luck, Tony]

On Mon, Jun 08, 2026 at 04:26:36PM -0700, Reinette Chatre wrote:
> 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?

Yes. I will add.

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

-Tony