[PATCH v6 10/10] Documentation/filesystems/resctrl: Add footnote for telemetry fstab mount caveat

Tony Luck
2026-04-29T18:49:24Z

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@intel.com>
---
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.
+
"mon_hw_id":
Available only with debug option. The identifier used by hardware
for the monitor group. On x86 this is the RMID.
--
2.53.0