Re: [PATCH v14 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG

Wei Wang
2017-08-18T07:37:15Z

On 08/18/2017 10:22 AM, Michael S. Tsirkin wrote:
> +static void send_balloon_page_sg(struct virtio_balloon *vb,
> + struct virtqueue *vq,
> + void *addr,
> + uint32_t size)
> +{
> + unsigned int len;
> + int ret;
> +
> + do {
> + ret = add_one_sg(vq, addr, size);
> + virtqueue_kick(vq);
> + wait_event(vb->acked, virtqueue_get_buf(vq, &len));
> + /*
> + * It is uncommon to see the vq is full, because the sg is sent
> + * one by one and the device is able to handle it in time. But
> + * if that happens, we go back to retry after an entry gets
> + * released.
> + */
> Why send one by one though? Why not batch some s/gs and wait for all
> of them to be completed? If memory if fragmented, waiting every time is
> worse than what we have now (VIRTIO_BALLOON_ARRAY_PFNS_MAX at a time).
>

OK, I'll do batching in some fashion.

Best,
Wei