On Thu, Oct 09, 2014 at 01:50:52PM +0530, Preeti U Murthy wrote: > >> SMT 8 on Power8 can help/hinder workloads. Hence we dynamically switch > >> the modes at runtime. > > > > That's just a horrible piece of crap hack and you deserve any and all > > pain you get from doing it. > > > > Randomly removing/adding cpus like that is horrible and makes a mockery > > of all the affinity interfaces we have. > > We observed this on ubuntu kernel, in which systemd explicitly mounts > cgroup controllers under a child cgroup identified by the user pid. > Since we had not observed this additional cgroup being added under the > hood, it came as a surprise to us that cgroup/cpuset handling in the > kernel should indeed kick in. > > At best we expect hotplug to be handled well if the users have not > explicitly configured cpusets, hence implicitly specifying that task > affinity is for all online cpus. This is indeed the case today, so that > is good. > > However what remains to be answered is that the V2 of cgroup design - > the default hierarchy, tracks hotplug operations for children cgroups as > well. Tejun, Li, will not the concerns that Peter raised above hold for > the default hierarchy as well? None of this addresses the piece of crap thing you did with power8. You cannot just make CPUs go away at random. -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
