Re: [PATCH v4 6/7] fs/resctrl: Document that automatic counter assignment is best effort

Reinette Chatre
2026-03-27T16:26:14Z

Hi Ben,

On 3/26/26 10:25 AM, Ben Horgan wrote:
> When using automatic counter assignment it's useful for a user to know
> which counters they can expect to be assigned on group creation.
>
> Document that automatic counter assignment is best effort and how to
> discover any assignment failures.
>
> Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
>
> Hi Reinette,
> I've just taken your suggested paragraph with a minor tweak (s/scenario/a
> scenario/) and moved it above the examples as I think it makes sense to
> keep examples last in each section.
> ---
> Documentation/filesystems/resctrl.rst | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index ba609f8d4de5..68cada238844 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -472,6 +472,12 @@ with the following files:
> "1":
> Auto assignment is enabled.
>
> + Automatic counter assignment is done with best effort. If auto
> + assignment is enabled but there are not enough available counters then
> + monitor group creation could succeed while one or more events belonging
> + to the group may not have a counter assigned. Consult last_cmd_status

"not have a counter assigned" -> "not have a counter assigned in all domains"?

> + for details during such a scenario.

While last_cmd_status would indicate a failure it is best for user space to
consult mbm_L3_assignments for the accurate counter assignment state ("the
details"). It is starting to sound like the documentation is directing user space
to last_cmd_status for state and I would like to avoid this. How about replacing
"Consult last_cmd_status ..." sentence with "Consult mbm_L3_assignments for
counter assignment states of the new group."?

> +
> Example::
>
> # echo 0 > /sys/fs/resctrl/info/L3_MON/mbm_assign_on_mkdir

Reinette