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Re: [Xen-devel] Xen Platform QoS design discussion

>>> On 02.05.14 at 14:30, <dongxiao.xu@xxxxxxxxx> wrote:
>>  -----Original Message-----
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: Friday, May 02, 2014 5:24 PM
>> To: Xu, Dongxiao
>> Cc: Andrew Cooper(andrew.cooper3@xxxxxxxxxx); Ian Campbell;
>> xen-devel@xxxxxxxxxxxxx 
>> Subject: RE: Xen Platform QoS design discussion
>> >>> On 01.05.14 at 02:56, <dongxiao.xu@xxxxxxxxx> wrote:
>> >> From: Ian Campbell [mailto:Ian.Campbell@xxxxxxxxxx]
>> >> Have you asked yourself whether this information even needs to be
>> >> exposed all the way up to libxl? Who are the expected consumers of this
>> >> interface? Are they low-level CLI tools (i.e. like xenpm is) or are you
>> >> expecting toolstacks to plumb this information all the way up to their
>> >> GUI or CLI (e.g. xl or virsh)?
>> >
>> > The information returned to libxl users is the cache utilization for a
>> > certain domain in certain socket, and the main consumers are cloud users 
> like
>> > openstack, etc. Of course, we will also provide an xl command to present 
> such
>> > information.
>> To me this doesn't really address the question Ian asked, yet knowing
>> who's going to be the consumer of the data is also quite relevant for
>> answering your original question on the method to obtain that data.
>> Obviously, if the main use of it is per-domain, a domctl would seem like
>> a suitable approach despite the data being more of sysctl kind. But if
>> a global view would be more important, that model would seem to make
>> life needlessly hard for the consumers. In turn, if using a domctl, I tend
>> to agree that not using shared pages would be preferable; iirc their use
>> was mainly suggested because of the size of the data.
> From the discussion with openstack developers, on certain cloud host, all 
> running VM's information (e.g., domain ID) will be stored in a database, and 
> openstack software will use libvirt/XenAPI to query specific domain 
> information. That libvirt/XenAPI API interface basically accepts the domain 
> ID as input parameter and get the domain information, including the platform 
> QoS one.
> Based on above information, I think we'd better design the QoS hypercall 
> per-domain.

If you think that this is going to be the only (or at least prevalent)
usage model, that's probably okay then. But I'm a little puzzled that
all this effort is just for a single, rather specific consumer. I thought
that if this is so important to Intel there would be wider interested


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