* Michal Hocko <mhocko@xxxxxxxxxx> [2020-07-01 10:42:00]: > > > > > 2. Also existence of dummy node also leads to inconsistent information. The > > number of online nodes is inconsistent with the information in the > > device-tree and resource-dump > > > > 3. When the dummy node is present, single node non-Numa systems end up showing > > up as NUMA systems and numa_balancing gets enabled. This will mean we take > > the hit from the unnecessary numa hinting faults. > > I have to say that I dislike the node online/offline state and directly > exporting that to the userspace. Users should only care whether the node > has memory/cpus. Numa nodes can be online without any memory. Just > offline all the present memory blocks but do not physically hot remove > them and you are in the same situation. If users are confused by an > output of tools like numactl -H then those could be updated and hide > nodes without any memory&cpus. > > The autonuma problem sounds interesting but again this patch doesn't > really solve the underlying problem because I strongly suspect that the > problem is still there when a numa node gets all its memory offline as > mentioned above. > > While I completely agree that making node 0 special is wrong, I have > still hard time to review this very simply looking patch because all the > numa initialization is so spread around that this might just blow up > at unexpected places. IIRC we have discussed testing in the previous > version and David has provided a way to emulate these configurations > on x86. Did you manage to use those instruction for additional testing > on other than ppc architectures? > I have tried all the steps that David mentioned and reported back at https://lore.kernel.org/lkml/20200511174731.GD1961@xxxxxxxxxxxxxxxxxx/t/#u As a summary, David's steps are still not creating a memoryless/cpuless on x86 VM. I have tried booting with Numa/non-numa on all the x86 machines that I could get to. -- Thanks and Regards Srikar Dronamraju
