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

["Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>]

> -----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.

Thanks,
Dongxiao




> 
> Jan


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