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Commit ce21a029 authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
Browse files

vhost_net: determine whether or not to use zerocopy at one time 



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 determining zerocopy once by checking all
conditions at one time before.

Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c49e4e57

drivers/vhost/net.c

+20 −27
Original line number Diff line number Diff line
@@ -404,26 +404,19 @@ 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);



		/* use msg_control to pass vhost zerocopy ubuf info to skb */

		if (zcopy_used) {

			vq->heads[nvq->upend_idx].id = head;

			if (!vhost_net_tx_select_zcopy(net) ||

			    len < VHOST_GOODCOPY_LEN) {

				/* copy don't need to wait for DMA done */

				vq->heads[nvq->upend_idx].len =

							VHOST_DMA_DONE_LEN;

				msg.msg_control = NULL;

				msg.msg_controllen = 0;

				ubufs = NULL;

			} else {

			struct ubuf_info *ubuf;

			ubuf = nvq->ubuf_info + nvq->upend_idx;



				vq->heads[nvq->upend_idx].len =

					VHOST_DMA_IN_PROGRESS;

			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;
@@ -431,15 +424,15 @@ static void handle_tx(struct vhost_net *net) 
			msg.msg_controllen = sizeof(ubuf);

			ubufs = nvq->ubufs;

			kref_get(&ubufs->kref);

			}

			nvq->upend_idx = (nvq->upend_idx + 1) % UIO_MAXIOV;

		} else

		} else {

			msg.msg_control = NULL;

			ubufs = NULL;

		}

		/* TODO: Check specific error and bomb out unless ENOBUFS? */

		err = sock->ops->sendmsg(NULL, sock, &msg, len);

		if (unlikely(err < 0)) {

			if (zcopy_used) {

				if (ubufs)

				vhost_net_ubuf_put(ubufs);

				nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)

					% UIO_MAXIOV;