From: Peter Zijlstra <peterz@infradead.org>
To: Nikhil Rao <ncrao@google.com>
Cc: Ingo Molnar <mingo@elte.hu>, Mike Galbraith <efault@gmx.de>,
linux-kernel@vger.kernel.org,
"Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>,
Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
Stephan Barwolf <stephan.baerwolf@tu-ilmenau.de>
Subject: Re: [PATCH v1 00/19] Increase resolution of load weights
Date: Fri, 13 May 2011 09:19:47 +0200 [thread overview]
Message-ID: <1305271187.17430.8.camel@twins> (raw)
In-Reply-To: <BANLkTimsvvWqcGanJs688hytLx1_jb0itw@mail.gmail.com>
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.
prev parent reply other threads:[~2011-05-13 7:20 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-02 1:18 [PATCH v1 00/19] Increase resolution of load weights Nikhil Rao
2011-05-02 1:18 ` [PATCH v1 01/19] sched: introduce SCHED_POWER_SCALE to scale cpu_power calculations Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 02/19] sched: increase SCHED_LOAD_SCALE resolution Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 03/19] sched: use u64 for load_weight fields Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 04/19] sched: update cpu_load to be u64 Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 05/19] sched: update this_cpu_load() to return u64 value Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 06/19] sched: update source_load(), target_load() and weighted_cpuload() to use u64 Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 07/19] sched: update find_idlest_cpu() to use u64 for load Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 08/19] sched: update find_idlest_group() to use u64 Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 09/19] sched: update division in cpu_avg_load_per_task to use div_u64 Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 10/19] sched: update wake_affine path to use u64, s64 for weights Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 11/19] sched: update update_sg_lb_stats() to use u64 Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 12/19] sched: Update update_sd_lb_stats() " Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 13/19] sched: update f_b_g() to use u64 for weights Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 14/19] sched: change type of imbalance to be u64 Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 15/19] sched: update h_load to use u64 Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 16/19] sched: update move_task() and helper functions to use u64 for weights Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 17/19] sched: update f_b_q() to use u64 for weighted cpuload Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 18/19] sched: update shares distribution to use u64 Nikhil Rao
2011-05-02 1:19 ` [PATCH v1 19/19] sched: convert atomic ops in shares update to use atomic64_t ops Nikhil Rao
2011-05-02 6:14 ` [PATCH v1 00/19] Increase resolution of load weights Ingo Molnar
2011-05-04 0:58 ` Nikhil Rao
2011-05-04 1:07 ` Nikhil Rao
2011-05-04 11:13 ` Ingo Molnar
2011-05-06 1:29 ` Nikhil Rao
2011-05-06 6:59 ` Ingo Molnar
2011-05-11 0:14 ` Nikhil Rao
2011-05-11 6:59 ` Ingo Molnar
2011-05-12 8:56 ` Nikhil Rao
2011-05-12 10:55 ` Ingo Molnar
2011-05-12 18:44 ` Nikhil Rao
2011-05-12 9:08 ` Peter Zijlstra
2011-05-12 17:30 ` Nikhil Rao
2011-05-13 7:19 ` Peter Zijlstra [this message]
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