Re: [PATCH V2 4/6] vhost_net: determine whether or not to use zerocopy at one time

Sergei Shtylyov
2013-08-30T18:35:50Z

Hello.

On 08/30/2013 08:29 AM, Jason Wang wrote:

> Currently, even if the packet length is smaller than VHOST_GOODCOPY_LEN, if
> upend_idx != done_idx we still set zcopy_used to true and rollback this choice
> later. This could be avoided by determine zerocopy once by checking all
> conditions at one time before.

> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> drivers/vhost/net.c | 46 +++++++++++++++++++---------------------------
> 1 files changed, 19 insertions(+), 27 deletions(-)

> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 8a6dd0d..ff60c2a 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -404,43 +404,35 @@ static void handle_tx(struct vhost_net *net)
> iov_length(nvq->hdr, s), hdr_size);
> break;
> }
> - zcopy_used = zcopy && (len >= VHOST_GOODCOPY_LEN ||
> - nvq->upend_idx != nvq->done_idx);
> +
> + zcopy_used = zcopy && len >= VHOST_GOODCOPY_LEN
> + && (nvq->upend_idx + 1) % UIO_MAXIOV != nvq->done_idx
> + && vhost_net_tx_select_zcopy(net);

Could you leave && on a first of two lines, matching the previous style?

>
> /* use msg_control to pass vhost zerocopy ubuf info to skb */
> if (zcopy_used) {
> + struct ubuf_info *ubuf;
> + ubuf = nvq->ubuf_info + nvq->upend_idx;
> +
> vq->heads[nvq->upend_idx].id = head;
[...]
> + vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
> + ubuf->callback = vhost_zerocopy_callback;
> + ubuf->ctx = nvq->ubufs;
> + ubuf->desc = nvq->upend_idx;
> + msg.msg_control = ubuf;
> + msg.msg_controllen = sizeof(ubuf);

'sizeof(ubuf)' where 'ubuf' is a pointer? Are you sure it shouldn't be
'sizeof(*ubuf)'?

WBR, Sergei