On Wed, Jun 22, 2022 at 12:09 AM Stefano Garzarella <sgarzare@xxxxxxxxxx> wrote:
>
> Limit the number of requests (4 per queue as for vdpa_sim_net) handled
> in a batch to prevent the worker from using the CPU for too long.
>
> Suggested-by: Eugenio Pérez <eperezma@xxxxxxxxxx>
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> ---
> drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> index a83a5c76f620..ac86478845b6 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> @@ -197,6 +197,7 @@ static bool vdpasim_blk_handle_req(struct vdpasim *vdpasim,
> static void vdpasim_blk_work(struct work_struct *work)
> {
> struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
> + bool reschedule = false;
> int i;
>
> spin_lock(&vdpasim->lock);
> @@ -206,11 +207,15 @@ static void vdpasim_blk_work(struct work_struct *work)
>
> for (i = 0; i < VDPASIM_BLK_VQ_NUM; i++) {
> struct vdpasim_virtqueue *vq = &vdpasim->vqs[i];
> + bool vq_work = true;
> + int reqs = 0;
>
> if (!vq->ready)
> continue;
>
> - while (vdpasim_blk_handle_req(vdpasim, vq)) {
> + while (vq_work) {
> + vq_work = vdpasim_blk_handle_req(vdpasim, vq);
> +
Is it better to check and exit the loop early here?
Thanks
> /* Make sure used is visible before rasing the interrupt. */
> smp_wmb();
>
> @@ -218,10 +223,18 @@ static void vdpasim_blk_work(struct work_struct *work)
> if (vringh_need_notify_iotlb(&vq->vring) > 0)
> vringh_notify(&vq->vring);
> local_bh_enable();
> +
> + if (++reqs > 4) {
> + vq_work = false;
> + reschedule = true;
> + }
> }
> }
> out:
> spin_unlock(&vdpasim->lock);
> +
> + if (reschedule)
> + schedule_work(&vdpasim->work);
> }
>
> static void vdpasim_blk_get_config(struct vdpasim *vdpasim, void *config)
> --
> 2.36.1
>
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