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Re: [Xen-devel] [PATCH RFC V2 24/45] xen: let vcpu_create() select processor
- To: Jan Beulich <JBeulich@xxxxxxxx>
- From: Juergen Gross <jgross@xxxxxxxx>
- Date: Thu, 16 May 2019 14:46:25 +0200
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- Cc: Tim Deegan <tim@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, Dario Faggioli <dfaggioli@xxxxxxxx>, Julien Grall <julien.grall@xxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>
- Delivery-date: Thu, 16 May 2019 12:46:37 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Openpgp: preference=signencrypt
On 16/05/2019 14:20, Jan Beulich wrote:
>>>> On 06.05.19 at 08:56, <jgross@xxxxxxxx> wrote:
>> --- a/xen/common/schedule.c
>> +++ b/xen/common/schedule.c
>> @@ -314,14 +314,42 @@ static struct sched_item *sched_alloc_item(struct vcpu
>> *v)
>> return NULL;
>> }
>>
>> -int sched_init_vcpu(struct vcpu *v, unsigned int processor)
>> +static unsigned int sched_select_initial_cpu(struct vcpu *v)
>> +{
>> + struct domain *d = v->domain;
>
> const (perhaps also the function parameter)?
Yes.
>
>> + nodeid_t node;
>> + cpumask_t cpus;
>
> To be honest, I'm not happy to see new on-stack instances of
> cpumask_t appear. Seeing ...
>
>> + cpumask_clear(&cpus);
>> + for_each_node_mask ( node, d->node_affinity )
>> + cpumask_or(&cpus, &cpus, &node_to_cpumask(node));
>> + cpumask_and(&cpus, &cpus, cpupool_domain_cpumask(d));
>> + if ( cpumask_empty(&cpus) )
>> + cpumask_copy(&cpus, cpupool_domain_cpumask(d));
>
> ... this fallback you use anyway, is there any issue with it also
> serving the case where zalloc_cpumask_var() fails?
Either that, or:
- just fail to create the vcpu in that case, as chances are rather
high e.g. the following arch_vcpu_create() will fail anyway
- take the scheduling lock and use cpumask_scratch
- (ab)use one of the available cpumasks in struct sched_unit which
are not in use yet
My preference would be using cpumask_scratch.
Juergen
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