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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>
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parent
c49e4e573b
commit
ce21a02913
1 changed files with 20 additions and 27 deletions
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@ -404,43 +404,36 @@ static void handle_tx(struct vhost_net *net)
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iov_length(nvq->hdr, s), hdr_size);
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break;
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}
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zcopy_used = zcopy && (len >= VHOST_GOODCOPY_LEN ||
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nvq->upend_idx != nvq->done_idx);
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zcopy_used = zcopy && len >= VHOST_GOODCOPY_LEN
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&& (nvq->upend_idx + 1) % UIO_MAXIOV !=
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nvq->done_idx
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&& vhost_net_tx_select_zcopy(net);
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/* use msg_control to pass vhost zerocopy ubuf info to skb */
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if (zcopy_used) {
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vq->heads[nvq->upend_idx].id = head;
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if (!vhost_net_tx_select_zcopy(net) ||
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len < VHOST_GOODCOPY_LEN) {
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/* copy don't need to wait for DMA done */
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vq->heads[nvq->upend_idx].len =
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VHOST_DMA_DONE_LEN;
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msg.msg_control = NULL;
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msg.msg_controllen = 0;
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ubufs = NULL;
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} else {
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struct ubuf_info *ubuf;
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ubuf = nvq->ubuf_info + nvq->upend_idx;
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struct ubuf_info *ubuf;
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ubuf = nvq->ubuf_info + nvq->upend_idx;
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vq->heads[nvq->upend_idx].len =
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VHOST_DMA_IN_PROGRESS;
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ubuf->callback = vhost_zerocopy_callback;
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ubuf->ctx = nvq->ubufs;
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ubuf->desc = nvq->upend_idx;
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msg.msg_control = ubuf;
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msg.msg_controllen = sizeof(ubuf);
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ubufs = nvq->ubufs;
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kref_get(&ubufs->kref);
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}
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vq->heads[nvq->upend_idx].id = head;
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vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
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ubuf->callback = vhost_zerocopy_callback;
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ubuf->ctx = nvq->ubufs;
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ubuf->desc = nvq->upend_idx;
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msg.msg_control = ubuf;
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msg.msg_controllen = sizeof(ubuf);
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ubufs = nvq->ubufs;
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kref_get(&ubufs->kref);
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nvq->upend_idx = (nvq->upend_idx + 1) % UIO_MAXIOV;
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} else
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} else {
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msg.msg_control = NULL;
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ubufs = NULL;
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}
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/* TODO: Check specific error and bomb out unless ENOBUFS? */
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err = sock->ops->sendmsg(NULL, sock, &msg, len);
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if (unlikely(err < 0)) {
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if (zcopy_used) {
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if (ubufs)
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vhost_net_ubuf_put(ubufs);
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vhost_net_ubuf_put(ubufs);
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nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
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% UIO_MAXIOV;
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}
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