Re: [PATCH 17/24] xen: credit2: soft-affinity awareness in runq_tickle()

[anshul makkar <anshul.makkar@citrix.com>]

On 05/09/16 15:55, Dario Faggioli wrote:
> On Thu, 2016-09-01 at 11:52 +0100, anshul makkar wrote:
>> On 17/08/16 18:19, Dario Faggioli wrote:
>>>
>>> +    /*
>>> +     * We're doing soft-affinity, and we know that the current
>>> vcpu on cpu
>>> +     * has a soft affinity. We now want to know whether cpu itself
>>> is in
>> Please can you explain the above statment. If the vcpu has soft
>> affinity
>> and its currently executing, doesn;t it always means that its running
>> on
>> one of the pcpu which is there in its soft affinity or hard affinity?
>>
> A vcpu will always run on a pcpu from its own hard-affinity (that's the
> definition of hard-affinity).
>
> On the other hand, a vcpu will, most of the time, run on a cpu from its
> own soft affinity, but can run on a cpu that is in its hard-affinity,
> but *IS NOT* in its soft-affinity.
>
> That's the definition of soft-affinity: the scheduler will try to run
> it there, but it that can't happen, it will run it will run it outside
> of it (but still within its hard-affinity, of course).
>
> So, yes, we know already that it's running in a cpu at least from its
> hard affinity, what is it exactly that you are not understanding?

If I put it simply ,  can  (X being a vcpu)
x {soft affinity pcpus} Intersect x { hard affinity pcpu} -> be Null or 
disjoint set ?
and

x{runnable pcpu} intersect (x{hard affinity pcpu} union x{soft affinity 
pcpu} ) -> be null or disjoint ??

>
>>> +     * such affinity. In fact, since we now that new (in
>>> runq_tickle()) is
>> Typo:   * such affinity. In fact, since now we know that new (in
>> runq_tickle()) is
>>
> Thanks. :-)

>>> +     */
>>
> Regards,
> Dario
>
Anshul Makkar

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