Messages in this thread | | | Subject | Re: [PATCH v1 00/19] Increase resolution of load weights | From | Peter Zijlstra <> | Date | Fri, 13 May 2011 09:19:47 +0200 |
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On Thu, 2011-05-12 at 10:30 -0700, Nikhil Rao wrote: > On Thu, May 12, 2011 at 2:08 AM, Peter Zijlstra <peterz@infradead.org> wrote: > > On Thu, 2011-05-05 at 18:29 -0700, Nikhil Rao wrote: > >> > It's a cost/benefit analysis and for 32-bit systems the benefits seem to be > >> > rather small, right? > >> > > >> > >> Yes, that's right. The benefits for 32-bit systems do seem to be limited. > > > > deep(er) hierarchies on 32 bits still require this, it would be good to > > verify that the cgroup mess created by the insanity called libvirt will > > indeed work as expected. > > > > I went through the libvirt docs and from what I understand, it creates > a hierarchy which is about 3 levels deep and has as many leaf nodes as > guest VMs.
That sounds about right with what I remember people telling me earlier ;-)
> Taking this graphic from > http://berrange.com/posts/2009/12/03/using-cgroups-with-libvirt-and-lxckvm-guests-in-fedora-12/ > > $ROOT > | > +- libvirt (all virtual machines/containers run by libvirtd) > | > +- lxc (all LXC containers run by libvirtd) > | | > | +- guest1 (LXC container called 'guest1') > | +- guest2 (LXC container called 'guest2') > | +- guest3 (LXC container called 'guest3') > | +- ... (LXC container called ...) > | > +- qemu (all QEMU/KVM containers run by libvirtd) > | > +- guest1 (QENU machine called 'guest1') > +- guest2 (QEMU machine called 'guest2') > +- guest3 (QEMU machine called 'guest3') > +- ... (QEMU machine called ...) > > Assuming the tg shares given to libvirt, lxc and qemu containers are > the defaults, the load balancer should be able to deal with the > current resolution on 32-bit. Back of the envelope calculations using > that approach I mentioned earlier (i.e. log_b(1024/NR_CPU)) says you > need > 64 VMs before you run out of resolution. I think that might be > too much to expect from a 8-cpu 32-bit machine ;-)
Quite so, get a real machine etc.. ;-) But then, there's always some weird people out there, but I think we can tell them to run a 64bit kernel.
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