Hi Babu, On Sat, Feb 22, 2025 at 12:43 AM Moger, Babu <bmoger@xxxxxxx> wrote: > > Hi Reinette, > > On 2/21/2025 4:48 PM, Reinette Chatre wrote: > > 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. > > In that case "mbm_assign_on_mkdir" seems on point and precise. > Thanks It also looks like counters are not assigned when a domain is hotplugged, so explicitly stating that it's on mkdir gets us off the hook for that. -Peter
