Xen performance kernel patches backported to 3.2 for Precise

Joseph Salisbury joseph.salisbury at canonical.com
Wed Nov 30 15:56:13 UTC 2011

On 11/30/2011 08:45 AM, Stefan Bader wrote:
> On 30.11.2011 12:38, Mike McClurg wrote:
>> Hello Kernel Team,
>> I have just created bug report #898112 [1]. This bug is related to a
>> kernel issue which negatively affects Xen performance on Ubuntu 11.04
>> and later. This issue is caused by the kernel incorrectly reporting the
>> cpufreq capabilities of the CPU to Xen, which prevents the hypervisor
>> from setting the CPU to the maximum frequency scaling.
>> A blog post describing the bug in detail can be found here [2]. The
>> patch series, which has been backported to 3.2 (and I believe 3.0 as
>> well) can be found here [3].
>> I ask the kernel team to consider including the 3.2 backport of this
>> branch in the Precise kernel, and possibly the Oneiric kernel as well,
>> if this is possible. Please feel free to contact me or Konrad (the patch
>> author) with any questions. Thanks,
>> Mike
> Hi Mike,
> if Konrad would/will manage to upstream those changes into 3.2, those would be
> picked up automatically. Just looking at the number of patches I would be quite
> careful to pick them from a non-upstream branch, even more because those all
> touch the acpi subsystem. And even being useful in Xen does not guarantee there
> is no side effect.
> I will look at them, but still would be careful and cannot make any promise
> right now.
> Thanks,
> Stefan
>> [1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/898112
>> [2] http://blog.xen.org/index.php/2011/11/29/baremetal-vs-xen-vs-kvm-redux/
>> [3]
>> http://git.kernel.org/?p=linux/kernel/git/konrad/xen.git;a=shortlog;h=refs/heads/devel/acpi-cpufreq.v4

Bug opened for this request as well:


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