[CentOS-virt] libvirt, xen PV, qemu-system-i386, root user

Fri Sep 11 23:35:48 UTC 2015
Karel Hendrych <k+centosvirt at karlos.cz>

Comparing simple dd bs=1M count=10000 on dom0 vs domU. Qemu driver is 
achieving pretty much the same like dom0.
Thanks
--
Karel

On 7.9.2015 21:45, Pasi Kärkkäinen wrote:
> On Mon, Sep 07, 2015 at 05:47:39PM +0200, Karel Hendrych wrote:
>> ...
>>
>> changing from: <driver name='file'/> to: <driver name='tap2'/> makes
>> the domain start without QEMU.
>>
>> However I see much better performance with QEMU (close to dom0,
>> tested using simple dd writes) than with tap2 driver. Is that
>> expected?
>>
>
> How did you measure it? buffered or direct io?
>
>
> -- Pasi
>
>
>> What's best practise to file based storage on latest CentOS6-xen
>> (Kernel 3.18.17, Xen 4.4.2-7)
>>
>> Are there any guides around running QEMU on CentOS6-xen as non-root user?
>>
>> Cheers
>> --
>> Karel
>>
>> On 7.9.2015 17:42, Karel Hendrych wrote:
>>> Hi, spot on!
>>>
>>>
>>> On 6.9.2015 12:56, Pasi Kärkkäinen wrote:
>>>> On Sun, Sep 06, 2015 at 09:08:50AM +0200, Karel Hendrych wrote:
>>>>> Hi, after migrating to libvirt/libxl according to:
>>>>>
>>>>
>>>> Hi,
>>>>
>>>>> https://wiki.centos.org/HowTos/Xen/Xen4QuickStart/Xen4Libvirt
>>>>>
>>>>> I've noticed that my Xen PV domains are being launched by
>>>>> qemu-system-i386 running under root privileges.
>>>>>
>>>>> I am wondering why is this? Previously no qemu process was used.
>>>>>
>>>>> If qemu is needed for some reason, are there any guidelines for
>>>>> non-root operation?
>>>>>
>>>>
>>>> In general qemu is used for the following purposes:
>>>>
>>>> - for certain domU disk backend types (image files), and/or if there's
>>>> no blktap driver in dom0 kernel.
>>>> - domU graphical console (PVFB) VNC server, if it's enabled for the domU.
>>>>
>>>>
>>>>> --
>>>>> Karel Hendrych
>>>>
>>>>
>>>> -- Pasi
>>>>
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