On Fri, Oct 11, 2024 at 03:49:48PM -0500, Moger, Babu wrote: > > Is there some hardware limitation that would prevent > > re-using domain 1 counters 2 & 3 for some other group (RMID)? > > > > Or is this just a s/w implementation detail because > > you have a system wide allocator for counters? > > > > There is no hardware limitation. It is how resctrl is designed. > In case of Intel(with two sockets, 16 CLOSIDs), You can only create 16 > groups. Each group will have two domains(domain 0 for socket 0 and domain 1 > for socket 1). > > # cat schemata > MB:0=100;1=100 > L3:0=ffff;1=ffff; > > > We may have to think of addressing this sometime in the future. In this example, the hardware would support using the instances of counters 2 & 3 on socket 1 for a different group (RMID). But your code doesn't alllow it because the instances of counters 2 & 3 are active on socket 0. If you had a separate counter allocation pool for each domain you would not have this limitation. When counters 2 & 3 are freed on domain 1, they could be allocated to the domain 1 element of some other group. Maybe that isn't an interesting use case, so not worth doing? But if that is the goal, then there is no benefit in having /sys/fs/resctrl/info/L3_MON/mbm_assign_control allow different domains to choose different counter allocation policies. E.g. in this example from Documentation: /child_default_mon_grp/0=tl;1=l; This group allocated two counters (because domain 0 is counting both total and local). Domain 1 is only counting local, but that means a counter on domain 1 is sitting idle. It can't be used because the matching counter is active on domain 0. I.e. the user who chose this simply gave up being able to read total bandwidth on domain 1, but didn't get an extra counter in exchange for this sacrifice. That doesn't seem like a good deal. I see two options for improvement: 1) Implement per-domain allocation of counters. Then a counter freed in a domain becomes available for use in that domain for other groups. 2) Go all-in on the global counter model and simplify the syntax of mbm_assign_control to allocate the same counters in all domains. That would simplify the parsing code. -Tony
