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 <jasow...@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

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