Re: [Xen-devel] [PATCH v2] credit: generalize __vcpu_has_soft_affinity()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.03.15 at 10:53, <george.dunlap@xxxxxxxxxxxxx> wrote:
> On 03/06/2015 07:36 AM, Jan Beulich wrote:
>> As pointed out in the discussion of the patch at
>> http://lists.xenproject.org/archives/html/xen-devel/2015-02/msg03256.html 
>> generalizing the conditions here means code elsewhere doesn't need to
>> take into consideration internals of how load balancing in the credit
>> scheduler works.
>> 
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> ---
>> v2: Use VCPU2ONLINE(vc) (or really an open coded variant thereof)
>>     instead of cpu_online_map (suggested by Dario).
>> 
>> --- a/xen/common/sched_credit.c
>> +++ b/xen/common/sched_credit.c
>> @@ -292,11 +292,10 @@ __runq_remove(struct csched_vcpu *svc)
>>  static inline int __vcpu_has_soft_affinity(const struct vcpu *vc,
>>                                             const cpumask_t *mask)
>>  {
>> -    if ( cpumask_full(vc->cpu_soft_affinity)
>> -         || !cpumask_intersects(vc->cpu_soft_affinity, mask) )
>> -        return 0;
>> -
>> -    return 1;
>> +    return !cpumask_subset(cpupool_online_cpumask(vc->domain->cpupool),
>> +                           vc->cpu_soft_affinity) &&
>> +           !cpumask_subset(vc->cpu_soft_affinity, vc->cpu_hard_affinity) &&
>> +           cpumask_intersects(vc->cpu_soft_affinity, mask);
> 
> It looks like the comment above this line could use changing too; perhaps:
> 
> ---
> 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

"hard" and "soft" appear to be swapped here. I corrected this,
please let me know if you disagree (in which case the patch would
need changing too).

> * There is an overlap between the soft affinity and the mask which is
> currently being considered.
> ---
> 
> With the comment updated:
> 
> Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

Thanks, Jan


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