Hi Babu, On 2/21/25 10:23 AM, Moger, Babu wrote: > Hi All, > > On 2/21/2025 11:14 AM, Dave Martin wrote: >> Hi, >> >> On Thu, Feb 20, 2025 at 09:08:17AM -0800, Reinette Chatre wrote: >>> Hi Dave, >>> >>> On 2/20/25 5:40 AM, Dave Martin wrote: >>>> On Thu, Feb 20, 2025 at 11:35:56AM +0100, Peter Newman wrote: >>>>> Hi Reinette, >>>>> >>>>> On Wed, Feb 19, 2025 at 6:55 PM Reinette Chatre >>>>> <reinette.chatre@xxxxxxxxx> wrote: >> >> [...] >> >>>>>> Could you please remind me how a user will set this flag? >>>>> >>>>> Quoting my original suggestion[1]: >>>>> >>>>> "info/L3_MON/mbm_assign_on_mkdir? >>>>> >>>>> boolean (parsed with kstrtobool()), defaulting to true?" >>>>> >>>>> After mount, any groups that got counters on creation would have to be >>>>> cleaned up, but at least that can be done with forward progress once >>>>> the flag is cleared. >>>>> >>>>> I was able to live with that as long as there aren't users polling for >>>>> resctrl to be mounted and immediately creating groups. For us, a >>>>> single container manager service manages resctrl. >> >> [...] >> >>>> +1 >>>> >>>> That's basically my position -- the auto-assignment feels like a >>>> _potential_ nuisance for ABMC-aware users, but it depends on what they >>>> are trying to do. Migration of non-ABMC-aware users will be easier for >>>> basic use cases if auto-assignment occurs by default (as in this >>>> series). >>>> >>>> Having an explicit way to turn this off seems perfectly reasonable >>>> (and could be added later on, if not provided in this series). >>>> >>>> >>>> What about the question re whether turning mbm_cntr_assign mode on >>>> should trigger auto-assignment? >>>> >>>> Currently turning this mode off and then on again has the effect of >>>> removing all automatic assignments for extant groups. This feels >>>> surprising and/or unintentional (?) >>> >>> Connecting to what you start off by saying I also see auto-assignment >>> as the way to provide a smooth transition for "non-ABMC-aware" users. >> >> I agree, and having this on by default also helps non-ABMC-aware users. >> >>> To me a user that turns this mode off and then on again can be >>> considered as a user that is "ABMC-aware" and turning it "off and then >>> on again" seems like an intuitive way to get to a "clean slate" >>> wrt counter assignments. This may also be a convenient way for >>> an "ABMC-aware" user space to unassign all counters and thus also >>> helpful if resctrl supports the flag that Peter proposed. The flag >>> seems to already keep something like this in its context with >>> a name of "mbm_assign_on_mkdir" that could be interpreted as >>> "only auto assign on mkdir"? >> >> Yes, that's reasonable. It could be a good idea to document this >> behaviour of switching the mbm_cntr_assign mode, if we think it is >> useful and people are likely to rely on it. >> >> Since mkdir is an implementation detail of the resctrl interface, I'd >> be tempted to go for a more generic name, say, >> "mbm_assign_new_mon_groups". But that's just bikeshedding. >> The proposed behaviour seems fine. >> >> Either way, if this is not included in this series, it could be added >> later without breaking anything. > > How about more generic "mbm_cntr_assign_auto" ? I would like to be careful to not make it _too_ generic. Dave already pointed out that users may be surprised that counters are not auto-assigned when switching between the different modes so using the the name to help highlight when this auto-assignment can be expected to happen seems very useful. Reinette
