On Fri, Aug 16, 2013 at 01:16:30PM +0800, Jason Wang wrote:
> We used to limit the max pending DMAs to prevent guest from pinning too many
> pages. But this could be removed since:
>
> - We have the sk_wmem_alloc check in both tun/macvtap to do the same work
> - This max pending check were almost useless since it was one done when there's
> no new buffers coming from guest. Guest can easily exceeds the limitation.
> - We've already check upend_idx != done_idx and switch to non zerocopy then. So
> even if all vq->heads were used, we can still does the packet transmission.
We can but performance will suffer.
>
> So remove this check completely.
>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> drivers/vhost/net.c | 13 -------------
> 1 files changed, 0 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index a035a89..ed3f165 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -38,8 +38,6 @@ MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero Copy TX;"
> * Using this limit prevents one virtqueue from starving others. */
> #define VHOST_NET_WEIGHT 0x80000
>
> -/* MAX number of TX used buffers for outstanding zerocopy */
> -#define VHOST_MAX_PEND 128
> #define VHOST_GOODCOPY_LEN 256
>
> /*
> @@ -372,17 +370,6 @@ static void handle_tx(struct vhost_net *net)
> break;
> /* Nothing new? Wait for eventfd to tell us they refilled. */
> if (head == vq->num) {
> - int num_pends;
> -
> - /* If more outstanding DMAs, queue the work.
> - * Handle upend_idx wrap around
> - */
> - num_pends = likely(nvq->upend_idx >= nvq->done_idx) ?
> - (nvq->upend_idx - nvq->done_idx) :
> - (nvq->upend_idx + UIO_MAXIOV -
> - nvq->done_idx);
> - if (unlikely(num_pends > VHOST_MAX_PEND))
> - break;
> if (unlikely(vhost_enable_notify(&net->dev, vq))) {
> vhost_disable_notify(&net->dev, vq);
> continue;
> --
> 1.7.1
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