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authorThomas Graf <tgraf@suug.ch>2013-12-13 15:22:21 +0100
committerJesse Gross <jesse@nicira.com>2014-01-06 15:53:17 -0800
commitbda56f143c9dc38ae7926ba21ebeb35359a6c051 (patch)
treeb3deb68ee339b9857796a51a4a68deba0188fede /net
parent8055a89cfa533f70bea5970727a50e220bb7d18e (diff)
openvswitch: Use skb_zerocopy() for upcall
Use of skb_zerocopy() can avoid the expensive call to memcpy() when copying the packet data into the Netlink skb. Completes checksum through skb_checksum_help() if not already done in GSO segmentation. 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 <tgraf@suug.ch> Signed-off-by: Jesse Gross <jesse@nicira.com>
Diffstat (limited to 'net')
-rw-r--r--net/openvswitch/datapath.c37
1 files changed, 29 insertions, 8 deletions
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 235acaeaedc..85578342d56 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -371,11 +371,11 @@ static size_t key_attr_size(void)
+ nla_total_size(28); /* OVS_KEY_ATTR_ND */
}
-static size_t upcall_msg_size(const struct sk_buff *skb,
- const struct nlattr *userdata)
+static size_t upcall_msg_size(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 */
@@ -397,6 +397,7 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
.snd_portid = upcall_info->portid,
};
size_t len;
+ unsigned int hlen;
int err, dp_ifindex;
dp_ifindex = get_dpifindex(dp);
@@ -421,7 +422,21 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
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(upcall_info->userdata, hlen);
user_skb = genlmsg_new_unicast(len, &info, GFP_ATOMIC);
if (!user_skb) {
err = -ENOMEM;
@@ -441,13 +456,19 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
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))) {
+ err = -ENOBUFS;
+ goto out;
+ }
+ nla->nla_len = nla_attr_size(skb->len);
- skb_copy_and_csum_dev(skb, nla_data(nla));
+ skb_zerocopy(user_skb, skb, skb->len, hlen);
- genlmsg_end(user_skb, upcall);
- err = genlmsg_unicast(ovs_dp_get_net(dp), user_skb, upcall_info->portid);
+ ((struct nlmsghdr *) user_skb->data)->nlmsg_len = user_skb->len;
+ err = genlmsg_unicast(ovs_dp_get_net(dp), user_skb, upcall_info->portid);
out:
kfree_skb(nskb);
return err;