Use of skb_zerocopy() can avoids the expensive call to memcpy()
when copying the packet data into the Netlink skb. Completes
checksum through skb_checksum_help() if needed.
Zerocopy is only performed if user space supported unaligned
Netlink messages. memory mapped netlink i/o is preferred over
zerocopy if it is set up.
Cost of upcall is significantly reduced from:
+ 7.48% vhost-8471 [k] memcpy
+ 5.57% ovs-vswitchd [k] memcpy
+ 2.81% vhost-8471 [k] csum_partial_copy_generic
to:
+ 5.72% ovs-vswitchd [k] memcpy
+ 3.32% vhost-5153 [k] memcpy
+ 0.68% vhost-5153 [k] skb_zerocopy
(megaflows disabled)
Signed-off-by: Thomas Graf <tg...@suug.ch>
Reviewed-by: Daniel Borkmann <dbork...@redhat.com>
---
net/openvswitch/datapath.c | 54 +++++++++++++++++++++++++++++++---------------
1 file changed, 37 insertions(+), 17 deletions(-)
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 72cdffb..237f7d7 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -108,10 +108,10 @@ int lockdep_ovsl_is_held(void)
#endif
static struct vport *new_vport(const struct vport_parms *);
-static int queue_gso_packets(struct net *, int dp_ifindex, struct sk_buff *,
- const struct dp_upcall_info *);
-static int queue_userspace_packet(struct net *, int dp_ifindex,
- struct sk_buff *,
+static int queue_gso_packets(struct datapath *, struct net *, int dp_ifindex,
+ struct sk_buff *, const struct dp_upcall_info *);
+static int queue_userspace_packet(struct datapath *, struct net *,
+ int dp_ifindex, struct sk_buff *,
const struct dp_upcall_info *);
/* Must be called with rcu_read_lock or ovs_mutex. */
@@ -292,9 +292,9 @@ int ovs_dp_upcall(struct datapath *dp, struct sk_buff *skb,
}
if (!skb_is_gso(skb))
- err = queue_userspace_packet(ovs_dp_get_net(dp), dp_ifindex,
skb, upcall_info);
+ err = queue_userspace_packet(dp, ovs_dp_get_net(dp),
dp_ifindex, skb, upcall_info);
else
- err = queue_gso_packets(ovs_dp_get_net(dp), dp_ifindex, skb,
upcall_info);
+ err = queue_gso_packets(dp, ovs_dp_get_net(dp), dp_ifindex,
skb, upcall_info);
if (err)
goto err;
@@ -310,7 +310,7 @@ err:
return err;
}
-static int queue_gso_packets(struct net *net, int dp_ifindex,
+static int queue_gso_packets(struct datapath *dp, struct net *net, int
dp_ifindex,
struct sk_buff *skb,
const struct dp_upcall_info *upcall_info)
{
@@ -327,7 +327,7 @@ static int queue_gso_packets(struct net *net, int
dp_ifindex,
/* Queue all of the segments. */
skb = segs;
do {
- err = queue_userspace_packet(net, dp_ifindex, skb, upcall_info);
+ err = queue_userspace_packet(dp, net, dp_ifindex, skb,
upcall_info);
if (err)
break;
@@ -381,10 +381,11 @@ static size_t key_attr_size(void)
}
static size_t upcall_msg_size(const struct sk_buff *skb,
- const struct nlattr *userdata)
+ const struct nlattr *userdata,
+ unsigned int hdrlen)
{
size_t size = NLMSG_ALIGN(sizeof(struct ovs_header))
- + nla_total_size(skb->len) /* OVS_PACKET_ATTR_PACKET */
+ + nla_total_size(hdrlen) /* OVS_PACKET_ATTR_PACKET */
+ nla_total_size(key_attr_size()); /* OVS_PACKET_ATTR_KEY */
/* OVS_PACKET_ATTR_USERDATA */
@@ -394,8 +395,8 @@ static size_t upcall_msg_size(const struct sk_buff *skb,
return size;
}
-static int queue_userspace_packet(struct net *net, int dp_ifindex,
- struct sk_buff *skb,
+static int queue_userspace_packet(struct datapath *dp, struct net *net,
+ int dp_ifindex, struct sk_buff *skb,
const struct dp_upcall_info *upcall_info)
{
struct ovs_header *upcall;
@@ -407,6 +408,7 @@ static int queue_userspace_packet(struct net *net, int
dp_ifindex,
.snd_portid = upcall_info->portid,
};
size_t len;
+ unsigned int hlen;
int err;
if (vlan_tx_tag_present(skb)) {
@@ -427,7 +429,21 @@ static int queue_userspace_packet(struct net *net, int
dp_ifindex,
goto out;
}
- len = upcall_msg_size(skb, upcall_info->userdata);
+ /* Complete checksum if needed */
+ if (skb->ip_summed == CHECKSUM_PARTIAL &&
+ (err = skb_checksum_help(skb)))
+ goto out;
+
+ /* Older versions of OVS user space enforce alignment of the last
+ * Netlink attribute to NLA_ALIGNTO which would require extensive
+ * padding logic. Only perform zerocopy if padding is not required.
+ */
+ if (dp->user_features & OVS_DP_F_UNALIGNED)
+ hlen = skb_zerocopy_headlen(skb);
+ else
+ hlen = skb->len;
+
+ len = upcall_msg_size(skb, upcall_info->userdata, hlen);
user_skb = genlmsg_new_unicast(len, &info, GFP_ATOMIC);
if (!user_skb) {
err = -ENOMEM;
@@ -447,13 +463,17 @@ static int queue_userspace_packet(struct net *net, int
dp_ifindex,
nla_len(upcall_info->userdata),
nla_data(upcall_info->userdata));
- nla = __nla_reserve(user_skb, OVS_PACKET_ATTR_PACKET, skb->len);
+ /* Only reserve room for attribute header, packet data is added
+ * in skb_zerocopy() */
+ if (!(nla = nla_reserve(user_skb, OVS_PACKET_ATTR_PACKET, 0)))
+ goto out;
+ nla->nla_len = nla_attr_size(skb->len);
+
+ skb_zerocopy(user_skb, skb, skb->len, hlen);
- skb_copy_and_csum_dev(skb, nla_data(nla));
+ ((struct nlmsghdr *) user_skb->data)->nlmsg_len = user_skb->len;
- genlmsg_end(user_skb, upcall);
err = genlmsg_unicast(net, user_skb, upcall_info->portid);
-
out:
kfree_skb(nskb);
return err;
--
1.8.3.1
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