Re: [PATCH v15 24/34] fs/resctrl: Report 'Unassigned' for MBM events in mbm_event mode
From: Moger, Babu
Date: Tue Jul 22 2025 - 20:27:17 EST
Hi Reinette,
On 7/22/2025 6:28 PM, Reinette Chatre wrote:
Hi Babu,
On 7/22/25 11:15 AM, Moger, Babu wrote:
Hi Reinette,
On 7/17/25 22:53, Reinette Chatre wrote:
Hi Babu,
On 7/8/25 3:17 PM, Babu Moger wrote:
When the "mbm_event" counter assignment mode is enabled, a hardware counter
must be assigned to read the event.
Report 'Unassigned' in case the user attempts to read the event without
assigning a hardware counter.
Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
---
Documentation/filesystems/resctrl.rst | 8 ++++++++
fs/resctrl/ctrlmondata.c | 6 ++++++
2 files changed, 14 insertions(+)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 446736dbd97f..4f5eb5bbd4b5 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -434,6 +434,14 @@ When monitoring is enabled all MON groups will also contain:
for the L3 cache they occupy). These are named "mon_sub_L3_YY"
where "YY" is the node number.
+ The "mbm_event" counter assignment mode offers "num_mbm_cntrs" number of
+ counters and allows users to assign counters to mon_hw_id, event pairs
+ enabling bandwidth monitoring for as long as the counter remains assigned.
+ The hardware will continue tracking the assigned counter until the user
+ manually unassigns it, ensuring that event data is not reset during this
+ period. An MBM event returns 'Unassigned' when the event does not have
+ a hardware counter assigned.
Most of this duplicates the "mbm_event" description added in patch #10. It should just
be sufficient to mention that this applies to "mbm_event" counter assignment mode
and then user can look up the main description in the doc.
The last sentence is related to this section and need an update to reflect behavior
when a CTRL_MON event is read and it or some of the MON groups do not have
counters assigned. The paragraph that precedes this does describe how the sum
works so this can tie into that.
Just added following text.
When the 'mbm_event' counter assignment mode is enabled, reading
Not sure how this will turn out ... if I understand correctly it follows a
paragraph that already starts with "The "mbm_event" counter assignment mode offers ..."
so there seems to be some redundancy.
There is no redundant text now. . Users can look up about "mbm_event"
from "mbm_assign_mode". Here is the complete diff.
diff --git a/Documentation/filesystems/resctrl.rst
b/Documentation/filesystems/resctrl.rst
index 446736dbd97f..01c33f62ce74 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -434,6 +434,12 @@ When monitoring is enabled all MON groups will also
contain:
for the L3 cache they occupy). These are named "mon_sub_L3_YY"
where "YY" is the node number.
+ When the 'mbm_event' counter assignment mode is enabled, reading
+ an MBM event of a MON group returns 'Unassigned' if no hardware
+ counter is assigned to it. For CTRL_MON groups, 'Unassigned' is
+ returned if none of the events in the CTRL_MON group or its
+ associated MON groups have assigned counters.
+
"mon_hw_id":
Available only with debug option. The identifier used by hardware
for the monitor group. On x86 this is the RMID.
an MBM event returns 'Unassigned' if no hardware counter is assigned
How about "reading an MBM event" -> "reading an MBM of a MON group" to
distinguish it from the text about CTRL_MON group that follows it?
to it. For CTRL_MON groups, 'Unassigned' is returned if none of the
events in the CTRL_MON group or its associated MON groups have assigned
counters.
Reinette