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If we use possible flags of: >>>>> >>>>> mbm_local_read_bytes a >>>>> mbm_local_write_bytes b >>>>> >>>>> Then mbm_assign_control can be used as: >>>>> # echo '//0=ab;1=b' >/sys/fs/resctrl/info/L3_MON/mbm_assign_control >>>>> # cat /sys/fs/resctrl/mon_data/mon_L3_00/mbm_local_read_bytes >>>>> >>>>> # cat /sys/fs/resctrl/mon_data/mon_L3_00/mbm_local_bytes >>>>> >>>>> >>>>> One issue would be when resctrl needs to support more than 26 events (no more flags available), >>>>> assuming that upper case would be used for "shared" counters (unless this interface is defined >>>>> differently and only few uppercase letters used for it). Would this be too low of a limit? > > As mentioned above, one possible issue with existing interface is that > it is limited to 26 events (assuming only lower case letters are used). The limit > is low enough to be of concern. Yes. Agree. > > .... > >>>> >>>> Alternatively, if we want to be able to expand beyond single letters, >>>> could we reserve one or more characters for extension purposes? >>>> >>>> If braces are forbidden by the syntax today, could we add support for >>>> something like the following later on, without breaking anything? >>>> >>>> # echo '//0={foo}{bar};1={bar}' >/sys/fs/resctrl/info/L3_MON/mbm_assign_control >>>> >>> > > Dave proposed a change in syntax that can (a) support unlimited events, > (b) be more intuitive than the one letter flags that may be hard to match > to the events they correspond to. Yea. Sounds good. > >>> Thank you for the suggestion. I think we may need something like this. >>> Babu, what do you think? >> >> I'm not quite clear on this. Do we know what 'foo' and 'bar' refer to? >> It is a random text? > > Not random text. It refers to the events. > > I do not know if braces is what will be settled on but a slight change in > example to make it match your series can be: > > # echo '//0={mbm_total_bytes}{mbm_local_bytes};1={mbm_local_bytes}' >/sys/fs/resctrl/info/L3_MON/mbm_assign_control > > With syntax like above there is no concern that we will run out of > flags and the events assigned are clear without needing to parse separate flags. Yes. We need to change our current "flag parsing". It should not be a problem. > For a system with a lot of events and domains this will become quite a lot > to parse though. > >> >> In his example from >> https://lore.kernel.org/lkml/Z643WdXYARTADSBy@e133380.arm.com/ >> -------------------------------------------------------------- >> The numbers are not supposed to have an hardware significance. >> >>     '//0=6' >> >> just "means assign some unused counter for domain 0, and create files >> in resctrl so I can configure and read it". > > Thanks for pointing this out. I missed that the idea was that the > configuration files are dynamically created. > >> >> The "6" is really just a tag for labelling the resulting resctrl >> file names so that the user can tell them apart.  It's not supposed >> to imply any specific hardware counter or event. > > Right. > >> ------------------------------------------------------------------ >> >> It seems that 'foo' and 'bar' are tags used to create files in /sys/fs/resctrl/info/L3_MON/. >> >> Given that, it looks like we're discussing entirely different things. > > I am still trying to understand how MPAM counters can be supported. > > Reinette Thanks Babu