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SubjectRe: [PATCH 11/13] blk-mq: allow the driver to pass in an affinity mask
On Tue, Jun 14, 2016 at 09:59:04PM +0200, Christoph Hellwig wrote:
> +static int blk_mq_create_mq_map(struct blk_mq_tag_set *set,
> + const struct cpumask *affinity_mask)
> +{
> + int queue = -1, cpu = 0;
> +
> + set->mq_map = kzalloc_node(sizeof(*set->mq_map) * nr_cpu_ids,
> + GFP_KERNEL, set->numa_node);
> + if (!set->mq_map)
> + return -ENOMEM;
> +
> + if (!affinity_mask)
> + return 0; /* map all cpus to queue 0 */
> +
> + /* If cpus are offline, map them to first hctx */
> + for_each_online_cpu(cpu) {
> + if (cpumask_test_cpu(cpu, affinity_mask))
> + queue++;

CPUs missing in an affinity mask are mapped to hctxs. Is that intended?

> + if (queue > 0)

Why this check?

> + set->mq_map[cpu] = queue;
> + }
> +
> + return 0;
> +}
> +

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