Hi Reinette, On 7/12/24 16:55, Reinette Chatre wrote: > Hi Babu, > > On 7/3/24 2:48 PM, Babu Moger wrote: >> Users can create as many monitor groups as RMIDs supported by the hardware. >> However, bandwidth monitoring feature on AMD system only guarantees that >> RMIDs currently assigned to a processor will be tracked by hardware. The >> counters of any other RMIDs which are no longer being tracked will be >> reset to zero. The MBM event counters return "Unavailable" for the RMIDs >> that are not tracked by hardware. So, there can be only limited number of >> groups that can give guaranteed monitoring numbers. With ever changing >> configurations there is no way to definitely know which of these groups >> are being tracked for certain point of time. Users do not have the option >> to monitor a group or set of groups for certain period of time without >> worrying about RMID being reset in between. >> >> The ABMC feature provides an option to the user to assign a hardware >> counter to an RMID and monitor the bandwidth as long as it is assigned. >> The assigned RMID will be tracked by the hardware until the user unassigns >> it manually. There is no need to worry about counters being reset during >> this period. Additionally, the user can specify a bitmask identifying the >> specific bandwidth types from the given source to track with the counter. >> >> Without ABMC enabled, monitoring will work in current mode without >> assignment option. >> >> Linux resctrl subsystem provides the interface to count maximum of two >> memory bandwidth events per group, from a combination of available total >> and local events. Keeping the current interface, users can enable a maximum >> of 2 ABMC counters per group. User will also have the option to enable only >> one counter to the group. If the system runs out of assignable ABMC >> counters, kernel will display an error. Users need to disable an already >> enabled counter to make space for new assignments. >> >> The feature can be detected via CPUID_Fn80000020_EBX_x00 bit 5. >> Bits Description >> 5 ABMC (Assignable Bandwidth Monitoring Counters) >> >> The feature details are documented in APM listed below [1]. >> [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming >> Publication # 24593 Revision 3.41 section 19.3.3.3 Assignable Bandwidth >> Monitoring (ABMC). >> >> Note: Checkpatch checks/warnings are ignored to maintain coding style. > > This note may be more appropriate below the '---' separator line. Sure. > >> >> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537 >> Signed-off-by: Babu Moger <babu.moger@xxxxxxx> >> --- > > Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx> -- Thanks Babu Moger
