Hi Reinette, On 5/3/24 16:16, Reinette Chatre wrote: > Hi Babu, > > On 5/3/2024 9:14 AM, Moger, Babu wrote: >> On 5/2/2024 6:00 PM, Reinette Chatre wrote: >>> On 4/17/2024 3:52 PM, Moger, Babu wrote: >>>> On 4/17/2024 3:56 PM, Peter Newman wrote: >>>>> On Wed, Apr 17, 2024 at 12:39 PM Moger, Babu <babu.moger@xxxxxxx> wrote: >>>>>> On 4/17/24 12:45, Peter Newman wrote: >>>>>>> On Thu, Mar 28, 2024 at 6:10 PM Babu Moger <babu.moger@xxxxxxx> wrote: >>>>>>>> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst >>>>>>>> index 2d96565501ab..64ec70637c66 100644 >>>>>>>> --- a/Documentation/arch/x86/resctrl.rst >>>>>>>> +++ b/Documentation/arch/x86/resctrl.rst >>>>>>>> @@ -328,6 +328,77 @@ with the following files: >>>>>>>> None of events are assigned on this mon group. This is a child >>>>>>>> monitor group of the non default control mon group. >>>>>>>> >>>>>>>> + Assignment state can be updated by writing to this interface. >>>>>>>> + >>>>>>>> + NOTE: Assignment on one domain applied on all the domains. User can >>>>>>>> + pass one valid domain and assignment will be updated on all the >>>>>>>> + available domains. >>>>>>> How would different assignments to different domains work? If the >>>>>>> allocations are global, then the allocated monitor ID is available to >>>>>>> all domains whether they use it or not. >>>>>> That is correct. >>>>>> [A] Hardware counters(max 2 per group) are allocated at the group level. >>>>>> So, those counters are available to all the domains on that group. I will >>>>>> maintain a bitmap at the domain level. The bitmap will be set on the >>>>>> domains where assignment is applied and IPIs are sent. IPIs will not be >>>>>> sent to other domains. >>>>> Unless the monitor allocation is scoped at the domain level, I don't >>>>> see much point in implementing the per-domain parsing today, as the >>>>> only benefit is avoiding IPIs to domains whose counters you don't plan >>>>> to read. >>>> >>>> In that case lets remove the domain specific assignments. We can avoid some code complexity. >>>> >>> >>> As I understand counters are scoped at the domain level and it is >>> an implementation choice to make the allocation global. (Similar to >>> the decision to make CLOSIDs global.) >>> >>> Could you please elaborate how you plan to remove domain specific >>> assignments? I do think it needs to remain as part of the user interface >>> so I wonder if this may look like only "*=<flags>" is supported on >>> these systems and attempting to assign an individual domain may fail >>> with "not supported". >> >> This series applies the assignment to all the domains. >> >> For example: >> >> # echo "//0=t" > /sys/fs/resctrl/info/L3_MON/mbm_assign_control >> >> User here wants to assign a monitor to total event on domain 0. >> But this series applies monitor to all the domains in the system. IPIs will be sent to all the domains. > > I would like to recommend against this. (a) this is not what the API > says will happen, (b) behavior like this may result in users having scripts > with syntax like above expecting changes to all domains and when/if > AMD or another architecture decides to implement per-domain assignment > it will break user space. Sure. We keep per-domain specific assignment. "//0=t" This will apply assignment only domain 0. "//*=t" This will apply assignment one all the domains. Hope it clarifies. > >> Basically this is equivalent to >> >> # echo "//*=t" > /sys/fs/resctrl/info/L3_MON/mbm_assign_control >> >> >> I was thinking of adding domain specific assignment in next version. >> That involves adding a new field in rdt_domain to keep track of >> assignment. Peter suggested it may not be much of a value add for his >> usage model. > > I do not have insight into how all users will end up using this. > > Reinette > -- Thanks Babu Moger
