Hi Tony, On 28/02/2023 17:44, Luck, Tony wrote: >>> Make it easy for the user to tell if Sub-NUMA Cluster is enabled by >>> providing an info/ file. >> >> I think what this is conveying to user-space is 'domain_id_is_numa_node'. > > That seems more architecturally neutral. I like it. > >> Does user-space need to know the number of ways? > > I don't know. Maybe some might. Perhaps there is some better name that > is architecturally neutral, but still has a numerical rather than boolean value? If we don't know what user-space needs this for, I'd prefer we don't expose it. It'll be a problem in the future if there is no single number we can put there. I don't see what the difference between 2 and 4 would be used for when setting up resctrl, unless you are choosing which numa-nodes to spread tasks over ... but the numa distance would be a much better number to base that decision on. User-space is able to perform the same calculation to find the snc_ways using the cache/index stuff and node entries in sysfs. >> Will this always be a single number, or will it ever be possible to have an SNC=2 and >> SNC=1 package in the same system? > > I sincerely hope that it is the same value across the system. Currently the > BIOS setup option to enable SNC doesn't have per-socket choices, it is > just an all-or-nothing choice. "2" isn't the only choice for number of SNC > nodes on a socket. "4" is (or will be) a choice. Yeah, in the arm world, partners get to make the decision on what is sane. Big-little means someone could do something that looks like SNC in on cluster, but not another. If we don't know what user-space needs it for, I'd prefer we don't expose it, just to avoid giving out rope to shoot ourselves in the foot with. Thanks, James
