On 22/11/16 01:03, Michal Hocko wrote: > On Wed 16-11-16 10:44:58, Balbir Singh wrote: >> In the absence of hotplug we use extra memory proportional to >> (possible_nodes - online_nodes) * number_of_cgroups. PPC64 has a patch >> to disable large consumption with large number of cgroups. This patch >> adds hotplug support to memory cgroups and reverts the commit that >> limited possible nodes to online nodes. > > I didn't get to read patches yet (I am currently swamped by emails after > longer vacation so bear with me) but this doesn't tell us _why_ we want > this and how much we can actaully save. The motivation was 3af229f2071f (powerpc/numa: Reset node_possible_map to only node_online_map) In general being dynamic is more > complex and most systems tend to have possible_nodes close to > online_nodes in my experience (well at least on most reasonable > architectures). I would also appreciate some highlevel description of > the implications. E.g. how to we synchronize with the hotplug operations > when iterating node specific data structures. I agree dynamic is more complex, but I think we'll begin to see a lot of more of it. The rules are not hard IMHO. From an implication perspective it means that we need to get/put_online_mem_nodes in certain paths - specifically mem_cgroup_alloc/free and mem_cgroup_init from what I can see so far Thanks for the review! Balbir Singh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>