On Fri, 13 Jul 2018, Roman Gushchin wrote: > > > > All cgroup v2 files do not need to be boolean and the only way you can add > > > > a subtree oom kill is to introduce yet another file later. Please make it > > > > tristate so that you can define a mechanism of default (process only), > > > > local cgroup, or subtree, and so we can avoid adding another option later > > > > that conflicts with the proposed one. This should be easy. > > > > > > David, we're adding a cgroup v2 knob, and in cgroup v2 a memory cgroup > > > either has a sub-tree, either attached processes. So, there is no difference > > > between local cgroup and subtree. > > > > > > > Uhm, what? We're talking about a common ancestor reaching its limit, so > > it's oom, and it has multiple immediate children with their own processes > > attached. The difference is killing all processes attached to the > > victim's cgroup or all processes under the oom mem cgroup's subtree. > > > > But it's a binary decision, no? > If memory.group_oom set, the whole sub-tree will be killed. Otherwise not. > No, if memory.max is reached and memory.group_oom is set, my understanding of your proposal is that a process is chosen and all eligible processes attached to its mem cgroup are oom killed. My desire for a tristate is so that it can be specified that all processes attached to the *subtree* are oom killed. With single unified hierarchy mandated by cgroup v2, we can separate descendant cgroups for use with other controllers and enforce memory.max by an ancestor. Making this a boolean value is only preventing it from becoming extensible. If memory.group_oom only is effective for the victim's mem cgroup, it becomes impossible to specify that all processes in the subtree should be oom killed as a result of the ancestor limit without adding yet another tunable.
