network and vnic qos

[Michal Privoznik]

On 14.07.2013 09:22, Ofri Masad wrote:
> Hi Giuseppe,
> 
> First of all, thanks for reviewing the design and the implementation.
> as for your comments, as I see it, we need to separate between what we can do (using libvirt) and what we would like to expose to the user.
> in my point of view, when a user is working with out engine (in appose to working directly with libvirt or vdsm) he expects different things.
> this is why we sometime take different choices from libvirt, to make the usage more simple/intuitive, to allow more complex abstraction 
> or to get better control over the full system.
> 
> specific comment inline
>      
> ----- Original Message -----
>> From: "Giuseppe Vallarelli" <gvallare at redhat.com>
>> To: arch at ovirt.org
>> Cc: "Ofri Masad" <omasad at redhat.com>, "Moti Asayag" <masayag at redhat.com>, "Mike Kolesnik" <mkolesni at redhat.com>,
>> "Michal Privoznik" <mprivozn at redhat.com>
>> Sent: Thursday, July 11, 2013 6:14:59 PM
>> Subject: network and vnic qos
>>
>> Hi Ofri, me, Moti and Mike have been looking carefully through the design
>> spec of the vnic profiles[0]
>> and lately to the network traffic shaping [1] which is very closely related.
>> A reason of concern is the current design of network qos table[2].
>>
>> First issue is the one related to the attributes associated to the traffic
>> shaping (either inbound
>> or outbound), I got the chance to talk with Michal (a libvirt developer in
>> Brno) which confirmed me
>> that the only compulsory attribute is average both burst and peak are
>> optional, also he told me that
>> libvirt doesn't provide any default values in case those are missing ones.
>> Looking at missingValue()
>> method in [3] seems that all 3 values are compulsory.
> 
> By not defining the other two values, we actually leave the decision to libvirt. that means that the different libvirt releases 
> may take different decision. when the user is setting a specific QoS for his network, he expect to see the same behavior over 
> all of the VNICs using that QoS (even if they are running on different libvirt versions). setting all three values in the engine
> allows us to force this unity. I will, however, add some default relations to the UI. so that when a user is setting the Average
> value, the Peak and Burst values will be automatically derived (but could be edited, of course).  

Libvirt doesn't set any of optional attributes if there's none set in
XML. We don't want to make any auto detection or AI for guessing the
correct values neither. I mean, for instance libvirt doesn't auto detect
the maximal bandwidth for a network but lets user to tell us the proper
values instead.

Michal