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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>
This commit is contained in:
Jason Wang 2013-09-02 16:40:59 +08:00 committed by David S. Miller
parent c49e4e573b
commit ce21a02913
1 changed files with 20 additions and 27 deletions
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47
drivers/vhost/net.c
View File

@ -404,43 +404,36 @@ 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;
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;
}