Hi Babu, On 7/8/25 6:27 AM, Moger, Babu wrote: > On 7/7/2025 5:35 PM, Moger, Babu wrote: >> On 7/3/25 11:21, Reinette Chatre wrote: >>> On 7/2/25 12:04 PM, Moger, Babu wrote: >>>> On 7/2/25 12:21, Reinette Chatre wrote: >>>>> On 7/2/25 9:42 AM, Moger, Babu wrote: >>>>>> On 6/25/25 18:39, Reinette Chatre wrote: >>>>>>> On 6/13/25 2:05 PM, Babu Moger wrote: >>>>>>>> BMEC (Bandwidth Monitoring Event Configuration) and mbm_event mode do not >>>>>>>> work simultaneously. >>>>>>> >>>>>>> Could you please elaborate why they do not work simultaneously? >>>>>> >>>>>> Changed the changelog. >>>>>> >>>>>> When mbm_event counter assignment mode is enabled, events are configured >>>>>> through the "event_filter" files under >>>>>> /sys/fs/resctrl/info/L3_MON/event_configs/. >>>>>> >>>>>> The default monitoring mode and with BMEC (Bandwidth Monitoring Event >>>>>> Configuration) support, events are configured using the files >>>>>> mbm_total_bytes_config or mbm_local_bytes_config in >>>>>> /sys/fs/resctrl/info/L3_MON/. >>>>> >>>>> A reasonable question here may be why not just keep using the existing >>>>> (BMEC supporting) event configuration files for event configuration? Why >>>>> are new event configuration files needed? >>>> >>>> New interface that enables users to read and write memory transaction >>>> events using human-readable strings, simplifying configuration and >>>> improving usability. >>> >>> I find the "simplifying configuration and improving usability" a bit vague >>> for a changelog. The cover letter already claims that ABMC and BMEC are >>> incompatible and links to some email discussions. I think it will be helpful >>> to summarize here why ABMC and BMEC are considered incompatible and then use >>> that as motivation to hide BMEC. The motivation in this changelog is to >>> "avoid confusion" but the motivation is stronger than that. >>> >> >> Changed the changelog. How does this look? >> >> "The default monitoring mode and with BMEC (Bandwidth Monitoring Event >> Configuration) support, events are configured using the files >> mbm_total_bytes_config or mbm_local_bytes_config in >> /sys/fs/resctrl/info/L3_MON/. >> >> When the mbm_event counter assignment mode is enabled, event configuration >> is handled via the event_filter files under >> /sys/fs/resctrl/info/L3_MON/event_configs/. This mode allows users to read >> and write memory transaction events using human-readable strings, making >> the interface easier to use and more intuitive. Going forward, this >> mechanism can support assigning multiple counters to RMID, event pairs and >> may be extended to allow flexible, user-defined event names. >> >> Given these changes, hide the BMEC-related files when the mbm_event >> counter assignment mode is enabled. Also, update the mon_features display >> accordingly." >> > > Here is another update. > > fs/resctrl: Hide the BMEC related files when mbm_event mode is enabled > > The default monitoring mode and with BMEC (Bandwidth Monitoring Event > Configuration) support, events are configured using the files > mbm_total_bytes_config or mbm_local_bytes_config in > /sys/fs/resctrl/info/L3_MON/. > > When the mbm_event counter assignment mode is enabled, event configuration is handled via the event_filter files under > /sys/fs/resctrl/info/L3_MON/event_configs/. This mode enables users to > configure memory transaction events using human-readable strings, providing a more intuitive and user-friendly interface. In the future, this mechanism could be extended to support assigning multiple counters to RMID-event pairs, as well as customizable, user-defined event names. Also, the presence of BMEC-related configuration files may cause confusion when the mbm_event counter assignment mode is enabled. > > To address this, these files are now hidden when the mode is active. > Additionally, the mon_features display has been updated to reflect this > change. I do not find a concrete motivation in this changelog. The terms "may cause confusion" and "providing a more intuitive and user-friendly interface." are vague and not something that I think provides a good motivation for disabling an entire interface. I aim to write a draft below that I hope will help make this changelog more convincing. Please do improve it: fs/resctrl: Disable BMEC event configuration when mbm_event mode is enabled The BMEC (Bandwidth Monitoring Event Configuration) feature enables per-domain event configuration. With BMEC the MBM events are configured using the mbm_total_bytes_config or mbm_local_bytes_config files in /sys/fs/resctrl/info/L3_MON/ and the per-domain event configuration affects all monitor resource groups. The mbm_event counter assignment mode enables counters to be assigned to RMID (i.e a monitor resource group), event pairs, with potentially unique event configurations associated with every counter. There may be systems that support both BMEC and mbm_event counter assignment mode, but resctrl supporting both concurrently will present a conflicting interface to the user with both per-domain and per RMID, event configurations active at the same time. mbm_event counter assignment provides most flexibility to user space and aligns with Arm's counter support. On systems that support both, disable BMEC event configuration when mbm_event mode is enabled by hiding the the mbm_total_bytes_config or mbm_local_bytes_config files when mbm_event mode is enabled. Ensure mon_features always displays accurate information about monitor features. Reinette
