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: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 8a6dd0d..3f89dea 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -404,43 +404,36 @@
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;
+ struct ubuf_info *ubuf;
+ ubuf = nvq->ubuf_info + nvq->upend_idx;
- 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);
- ubufs = nvq->ubufs;
- kref_get(&ubufs->kref);
- }
+ 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);
+ 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);
+ vhost_net_ubuf_put(ubufs);
nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
% UIO_MAXIOV;
}