>>> Umm, why do users of cpusets not want to be able to trigger memory >>> pressure notifications? >>> >> Because cpusets only deal with memory placement, not memory usage. > > The set of nodes that a thread is allowed to allocate from may face memory > pressure up to and including oom while the rest of the system may have a > ton of free memory. Your solution is to compile and mount memcg if you > want notifications of memory pressure on those nodes. Others in this > thread have already said they don't want to rely on memcg for any of this > and, as Anton showed, this can be tied directly into the VM without any > help from memcg as it sits today. So why implement a simple and clean > mempressure cgroup that can be used alone or co-existing with either memcg > or cpusets? > Forgot this one: Because there is a huge ongoing work going on by Tejun aiming at reducing the effects of orthogonal hierarchy. There are many controllers today that are "close enough" to each other (cpu, cpuacct; net_prio, net_cls), and in practice, it brought more problems than it solved. So yes, *maybe* mempressure is the answer, but it need to be justified with care. Long term, I think a saner notification API for memcg will lead us to a better and brighter future. There is also yet another aspect: This scheme works well for global notifications. If we would always want this to be global, this would work neatly. But as already mentioned in this thread, at some point we'll want this to work for a group of processes as well. At that point, you'll have to count how much memory is being used, so you can determine whether or not pressure is going on. You will, then, have to redo all the work memcg already does. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
