Re: [PATCH v2] credit: generalize __vcpu_has_soft_affinity()

[George Dunlap <george.dunlap@eu.citrix.com>]

On 03/06/2015 11:12 AM, Dario Faggioli wrote:
> On Fri, 2015-03-06 at 09:53 +0000, George Dunlap wrote:
>> On 03/06/2015 07:36 AM, Jan Beulich wrote:
> 
>> It looks like the comment above this line could use changing too;
>>
> It probably does.
> 
>> ---
>> Hard affinity balancing is always necessary and must never be skipped.
>> But soft affinity need only be considered when it has a functionally
>> different effect than other constraints (such as hard affinity, cpus
>> online, or cpupools).
>>
>> Soft affinity only needs to be considered if:
>> * The cpus in the cpupool are not a subset of soft affinity
>> * The hard affinity is not a subset of soft affinity
>> * There is an overlap between the soft affinity and the mask which is
>> currently being considered.
>> ---
> The original comment was more aimed at trying to make as evident as
> possible to the reader why the occurrence of a particular combination of
> hard and soft affinity makes using the latter pointless (perhaps it was
> not that effective at that, but that's another story! :-D).
> 
> So, if changing it, I'd go for something more 'high level'; something
> that helps the reader grasp more quickly what is the actual meaning of
> those _subsect() and _intersect() operations. Perhaps:
> 
> ---
> Hard affinity balancing is always necessary and must never be skipped.
> Soft affinity balancing is only useful if it, potentially, makes a
> difference.
> 
> In more details, there is no point checking soft affinity if:
> * there is no online pCPU in the domain's cpupool that is not in the
>   soft affinity mask
> * there is no pCPU in the hard affinity mask that is not in the soft
>   affinity mask
> * there is no overlapping between the soft affinity mask and the mask
>   being considered (which, in most cases, is the hard affinity mask)
> ---

I think what you've said here is almost exactly the same thing as what I
said, except using different words. (i.e., "X not a subset of Y" means
"there are X which are not in Y")

I don't mind necessarily, but I'm not sure you've actually accomplished
your purpose. :-)

 -George