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authorMichael S. Tsirkin <mst@redhat.com>2012-12-06 17:00:18 +0200
committerMichael S. Tsirkin <mst@redhat.com>2012-12-06 17:09:18 +0200
commitcedb9bdce099206290a2bdd02ce47a7b253b6a84 (patch)
treee30b69a7b94c6fe30272549f3c3ad6faf10bd37f /drivers/vhost
parent1280c27f8e29acf4af2da914e80ec27c3dbd5c01 (diff)
downloadblackbird-op-linux-cedb9bdce099206290a2bdd02ce47a7b253b6a84.tar.gz
blackbird-op-linux-cedb9bdce099206290a2bdd02ce47a7b253b6a84.zip
vhost-net: skip head management if no outstanding
For short packets zerocopy mode adds overhead of managing heads which isn't necessary: we could simly update used ring directly same as with zerocopy disabled. Things seem to run a bit faster if we detect and bypass head management when zcopy isn't used. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'drivers/vhost')
-rw-r--r--drivers/vhost/net.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 6a86deb39a72..aa76ca72606a 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -241,7 +241,7 @@ static void handle_tx(struct vhost_net *net)
size_t hdr_size;
struct socket *sock;
struct vhost_ubuf_ref *uninitialized_var(ubufs);
- bool zcopy;
+ bool zcopy, zcopy_used;
/* TODO: check that we are running from vhost_worker? */
sock = rcu_dereference_check(vq->private_data, 1);
@@ -319,8 +319,11 @@ static void handle_tx(struct vhost_net *net)
iov_length(vq->hdr, s), hdr_size);
break;
}
+ zcopy_used = zcopy && (len >= VHOST_GOODCOPY_LEN ||
+ vq->upend_idx != vq->done_idx);
+
/* use msg_control to pass vhost zerocopy ubuf info to skb */
- if (zcopy) {
+ if (zcopy_used) {
vq->heads[vq->upend_idx].id = head;
if (!vhost_net_tx_select_zcopy(net) ||
len < VHOST_GOODCOPY_LEN) {
@@ -348,7 +351,7 @@ static void handle_tx(struct vhost_net *net)
/* TODO: Check specific error and bomb out unless ENOBUFS? */
err = sock->ops->sendmsg(NULL, sock, &msg, len);
if (unlikely(err < 0)) {
- if (zcopy) {
+ if (zcopy_used) {
if (ubufs)
vhost_ubuf_put(ubufs);
vq->upend_idx = ((unsigned)vq->upend_idx - 1) %
@@ -362,7 +365,7 @@ static void handle_tx(struct vhost_net *net)
if (err != len)
pr_debug("Truncated TX packet: "
" len %d != %zd\n", err, len);
- if (!zcopy)
+ if (!zcopy_used)
vhost_add_used_and_signal(&net->dev, vq, head, 0);
else
vhost_zerocopy_signal_used(net, vq);
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