Hi Babu, On 7/8/25 3:17 PM, Babu Moger wrote: > Resctrl subsystem can support two monitoring modes, "mbm_event" or > "default". In mbm_event mode, monitoring event can only accumulate data > while it is backed by a hardware counter. In "default" mode, resctrl > assumes there is a hardware counter for each event within every CTRL_MON > and MON group. > > Introduce mbm_assign_mode resctrl file to switch between mbm_event and > default modes. > > Example: > To list the MBM monitor modes supported: > $ cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode > [mbm_event] > default > > To enable the "mbm_event" monitoring mode: "monitoring mode" -> "counter assignment mode"? > $ echo "mbm_event" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode > > To enable the "default" monitoring mode: > $ echo "default" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode > > MBM event counters are automatically reset as part of changing the mode. > Clear both architectural and non-architectural event states to prevent > overflow conditions during the next event read. Also clear assignable > counter configuration on all the domains. > > Signed-off-by: Babu Moger <babu.moger@xxxxxxx> > --- ... > --- > Documentation/filesystems/resctrl.rst | 22 +++++++- > fs/resctrl/internal.h | 2 + > fs/resctrl/monitor.c | 27 ++++++++++ > fs/resctrl/rdtgroup.c | 72 ++++++++++++++++++++++++++- > 4 files changed, 121 insertions(+), 2 deletions(-) > > diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst > index 2b2acb55d8b1..b8a4dbe061ea 100644 > --- a/Documentation/filesystems/resctrl.rst > +++ b/Documentation/filesystems/resctrl.rst > @@ -259,7 +259,8 @@ with the following files: > > "mbm_assign_mode": > The supported counter assignment modes. The enclosed brackets indicate which mode > - is enabled. > + is enabled. The MBM events associated with counters may reset when "mbm_assign_mode" > + is changed. > :: > > # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode > @@ -279,6 +280,15 @@ with the following files: > of counters available is described in the "num_mbm_cntrs" file. Changing the > mode may cause all counters on the resource to reset. > > + Moving to mbm_event counter assignment mode requires users to assign the counters > + to the events. Otherwise, the MBM event counters will return 'Unassigned' when read. > + > + The mode is beneficial for AMD platforms that support more CTRL_MON > + and MON groups than available hardware counters. By default, this > + feature is enabled on AMD platforms with the ABMC (Assignable Bandwidth > + Monitoring Counters) capability, ensuring counters remain assigned even > + when the corresponding RMID is not actively used by any processor. > + > "default": > > In default mode, resctrl assumes there is a hardware counter for each > @@ -288,6 +298,16 @@ with the following files: > result in misleading values or display "Unavailable" if no counter is assigned > to the event. > > + * To enable "mbm_event" monitoring mode: "monitoring mode" -> "counter assignment mode"? > + :: > + > + # echo "mbm_event" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode > + > + * To enable "default" monitoring mode: > + :: > + > + # echo "default" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode > + > "num_mbm_cntrs": > The maximum number of counters (total of available and assigned counters) in > each domain when the system supports mbm_event mode. Reinette
