Hi Tony, On 3/7/2024 9:57 AM, Luck, Tony wrote: >>> SNC2 enabled: >>> >>> $ cat /sys/fs/resctrl/info/L3_mon/ snc_nodes_per_l3_cache >>> 2 >>> >> >> This would be useful. I believe "SNC" is architecture specific? >> What if the file always exists and is named "nodes_per_l3_cache"? >> >> I assume that the internals of handling more nodes per L3 cache should >> be hidden from user space and it should not be necessary for user space >> to know if this is because of SNC or potentially some other mechanism on >> another platform? >> >> I think that may reduce fragmentation of resctrl .... not having >> resctrl look so different on different architectures but maintains >> the promise of a generic interface. >> >> I am not sure if this is specific to monitoring though, >> why not host file in /sys/fs/resctrl/info/L3 ? > > Reinette, > > On the name change - sure. It doesn't need the "snc_" prefix. > > The Intel implementation of SNC has far more effect on monitoring > than on control. The user can read separate cache occupancy and > memory bandwidth values for each SNC node. But cache allocation > bitmasks and memory throttling still have a single control point for > each L3 cache instance, not for each node. There are still some > impacts on control, e.g. each bit in a CAT bitmask represents > less actual space in the L3 cache. I understand the impact but I am trying to view this conceptually. The info directory exists to "contain information about the enabled resources" (as per documentation) and it seems appropriate to make this a property of the L3 resource. > > Maybe move it to the top level of the info/ directory: > > $ cat /sys/fs/resctrl/info/nodes_per_l3_cache > 3 Thinking about it even differently. The goal is to give information to userspace so we need to think about what would help user space? For example, what if there is a file in info that shows which CPUs are associated with each domain? Reinette
