On 23/11/16 18:25, Michal Hocko wrote: > On Wed 23-11-16 15:36:51, 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. > > Balbir, > I have asked this in the previous version but there still seems to be a > lack of information of _why_ do we want this, _how_ much do we save on > the memory overhead on most systems and _why_ the additional complexity > is really worth it. Please make sure to add all this in the cover > letter. > The data is in the patch referred to in patch 3. The order of waste was 200MB for 400 cgroup directories enough for us to restrict possible_map to online_map. These patches allow us to have a larger possible map and allow onlining nodes not in the online_map, which is currently a restriction on ppc64. A typical system that I use has about 100-150 directories, depending on the number of users/docker instances/configuration/virtual machines. These numbers will only grow as we pack more of these instances on them. >From a complexity view point, the patches are quite straight forward. > I still didn't get to look into those patches because I am swamped with > other things but to be honest I do not really see a strong justification > to make it high priority for me. > I am OK if you need more time to review them, but I've been pushing them to fix the cases I've mentioned above. 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>