On Thu, Sep 20, 2012 at 11:26 AM, Tejun Heo <tj@xxxxxxxxxx> wrote: > Hello, > > On Wed, Sep 19, 2012 at 06:33:15PM -0700, Andy Lutomirski wrote: >> [grr. why does gmane scramble addresses?] > > You can append /raw to the message url and see the raw mssage. > > http://article.gmane.org/gmane.linux.kernel.containers/23802/raw Thanks! > >> > I think this level of flexibility should be enough for most use >> > cases. If someone disagrees, please voice your objections now. >> >> OK, I'll bite. >> >> I have a server that has a whole bunch of cores. A small fraction of >> those cores are general purpose and run whatever they like. The rest >> are tightly controlled. >> >> For simplicity, we have two cpusets that we use. The root allows all >> cpus. The other one only allows the general purpose cpus. We shove >> everything into the general-purpose-only cpuset, and then we move >> special stuff back to root. (We also shove some kernel threads into a >> non-root cpuset using the 'cset' tool.) > > Using root for special stuff probably isn't a good idea and moving > bound kthreads into !root cgroups is already disallowed. Agreed. I do it this way because it's easy and it works. I can change it in the future if needed. > >> Enter systemd, which wants a hierarchy corresponding to services. If we >> were to use it, we might end up violating its hierarchy. >> >> Alternatively, if we started using memcg, then we might have some tasks >> to have more restrictive memory usage but less restrictive cpu usage. >> >> As long as we can still pull this off, I'm happy. > > IIUC, you basically want just two groups w/ cpuset and use it for > loose cpu ioslation for high priority jobs. Structure-wise, I don't > think it's gonna be a problem although using root for special stuff > would need to change. Right. But what happens when multiple hierarchies go away and I lose control of the structure? If systemd or whatever sticks my whole session or my service (or however I organize it) into cgroup /whatever, then either I can put my use-all-cpus tasks into /whatever/everything or I can step outside the hierarchy and put them into /everything. The former doesn't work, because <quote> The following rules apply to each cpuset: - Its CPUs and Memory Nodes must be a subset of its parents. </quote> The latter might confuse systemd. My real objection might be to that requirement a cpuset can't be less restrictive than its parents. Currently I can arrange for a task to simultaneously have a less restrictive cpuset and a more restrictive memory limit (or to stick it into a container or whatever). If the hierarchies have to correspond, this stops working. --Andy -- 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
