On Mon, Dec 5, 2022 at 4:59 PM Xie Yongji <xieyongji@xxxxxxxxxxxxx> wrote:
>
> This brings current interrupt affinity spreading mechanism
> to vduse device. We will make use of irq_create_affinity_masks()
> to create an irq callback affinity mask for each virtqueue of
> vduse device. Then we will choose the CPU which has the lowest
> number of interrupt allocated in the affinity mask to run the
> irq callback.
This seems a balance mechanism but it might not be the semantic of the
affinity or any reason we need to do this? I guess we should use at
least round-robin in this case.
>
> Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
> ---
> drivers/vdpa/vdpa_user/vduse_dev.c | 50 ++++++++++++++++++++++++++++++
> 1 file changed, 50 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index d126f3e32a20..90c2896039d9 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -23,6 +23,7 @@
> #include <linux/nospec.h>
> #include <linux/vmalloc.h>
> #include <linux/sched/mm.h>
> +#include <linux/interrupt.h>
> #include <uapi/linux/vduse.h>
> #include <uapi/linux/vdpa.h>
> #include <uapi/linux/virtio_config.h>
> @@ -58,6 +59,8 @@ struct vduse_virtqueue {
> struct work_struct inject;
> struct work_struct kick;
> int irq_effective_cpu;
> + struct cpumask irq_affinity;
> + spinlock_t irq_affinity_lock;
Ok, I'd suggest to squash this into patch 5 to make it more easier to
be reviewed.
> };
>
> struct vduse_dev;
> @@ -123,6 +126,7 @@ struct vduse_control {
>
> static DEFINE_MUTEX(vduse_lock);
> static DEFINE_IDR(vduse_idr);
> +static DEFINE_PER_CPU(unsigned long, vduse_allocated_irq);
>
> static dev_t vduse_major;
> static struct class *vduse_class;
> @@ -710,6 +714,49 @@ static u32 vduse_vdpa_get_generation(struct vdpa_device *vdpa)
> return dev->generation;
> }
>
> +static void vduse_vq_update_effective_cpu(struct vduse_virtqueue *vq)
> +{
> + unsigned int cpu, best_cpu;
> + unsigned long allocated, allocated_min = UINT_MAX;
> +
> + spin_lock(&vq->irq_affinity_lock);
> +
> + best_cpu = vq->irq_effective_cpu;
> + if (best_cpu != -1)
> + per_cpu(vduse_allocated_irq, best_cpu) -= 1;
> +
> + for_each_cpu(cpu, &vq->irq_affinity) {
> + allocated = per_cpu(vduse_allocated_irq, cpu);
> + if (!cpu_online(cpu) || allocated >= allocated_min)
> + continue;
> +
> + best_cpu = cpu;
> + allocated_min = allocated;
> + }
> + vq->irq_effective_cpu = best_cpu;
> + per_cpu(vduse_allocated_irq, best_cpu) += 1;
> +
> + spin_unlock(&vq->irq_affinity_lock);
> +}
> +
> +static void vduse_vdpa_set_irq_affinity(struct vdpa_device *vdpa,
> + struct irq_affinity *desc)
> +{
> + struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> + struct irq_affinity_desc *affd = NULL;
> + int i;
> +
> + affd = irq_create_affinity_masks(dev->vq_num, desc);
> + if (!affd)
Let's add a comment on the vdpa config ops to say set_irq_affinity()
is best effort.
Thanks
> + return;
> +
> + for (i = 0; i < dev->vq_num; i++) {
> + cpumask_copy(&dev->vqs[i]->irq_affinity, &affd[i].mask);
> + vduse_vq_update_effective_cpu(dev->vqs[i]);
> + }
> + kfree(affd);
> +}
> +
> static int vduse_vdpa_set_map(struct vdpa_device *vdpa,
> unsigned int asid,
> struct vhost_iotlb *iotlb)
> @@ -760,6 +807,7 @@ static const struct vdpa_config_ops vduse_vdpa_config_ops = {
> .get_config = vduse_vdpa_get_config,
> .set_config = vduse_vdpa_set_config,
> .get_generation = vduse_vdpa_get_generation,
> + .set_irq_affinity = vduse_vdpa_set_irq_affinity,
> .reset = vduse_vdpa_reset,
> .set_map = vduse_vdpa_set_map,
> .free = vduse_vdpa_free,
> @@ -1380,6 +1428,8 @@ static int vduse_dev_init_vqs(struct vduse_dev *dev, u32 vq_align, u32 vq_num)
> INIT_WORK(&dev->vqs[i]->kick, vduse_vq_kick_work);
> spin_lock_init(&dev->vqs[i]->kick_lock);
> spin_lock_init(&dev->vqs[i]->irq_lock);
> + spin_lock_init(&dev->vqs[i]->irq_affinity_lock);
> + cpumask_setall(&dev->vqs[i]->irq_affinity);
> }
>
> return 0;
> --
> 2.20.1
>
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