[PATCH net-next 2/2] openvswitch: Use skb_zerocopy() to prepare skb for upcall
From: Thomas Graf <tgraf@suug.ch>
Date: 2013-07-25 12:43:53
Subsystem:
networking [general], openvswitch, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Aaron Conole, Eelco Chaudron, Ilya Maximets, Linus Torvalds
From: Thomas Graf <redacted>
Use of skb_zerocopy() avoids the expensive call to memcpy() when
copying the packet data into the Netlink skb. Completes checksum
through skb_checksum_help() if needed (typicall packet input from
software device) which invalidates some of the gains again.
Stock-RX
- 38.30% swapper [kernel.kallsyms] [k] memcpy
- memcpy
+ 87.46% queue_userspace_packet
+ 12.54% nla_put
+ 24.72% ovs-vswitchd libc-2.17.so [.] __memcpy_ssse3_back
+ 13.80% ovs-vswitchd [kernel.kallsyms] [k] memcpy
- 7.68% ksoftirqd/2 [kernel.kallsyms] [k] memcpy
- memcpy
+ 85.83% queue_userspace_packet
+ 14.17% nla_put
- 7.06% ksoftirqd/3 [kernel.kallsyms] [k] memcpy
- memcpy
+ 84.85% queue_userspace_packet
+ 15.15% nla_put
- 4.41% ksoftirqd/0 [kernel.kallsyms] [k] memcpy
- memcpy
+ 83.48% queue_userspace_packet
+ 16.52% nla_put
Zerocopy-RX
+ 50.35% ovs-vswitchd libc-2.17.so [.] __memcpy_ssse3_back
- 27.78% ovs-vswitchd [kernel.kallsyms] [k] memcpy
- memcpy
+ 74.53% ovs_packet_cmd_execute
+ 24.11% nla_put
+ 0.93% ovs_flow_cmd_new_or_set
+ 13.49% swapper [kernel.kallsyms] [k] memcpy
+ 1.45% ksoftirqd/3 [kernel.kallsyms] [k] memcpy
+ 1.20% ksoftirqd/2 [kernel.kallsyms] [k] memcpy
10Gb remote pktgen, 1200 bytes, randomized flows, w/ UDPCSUM:
Hits Missed Lost
Stock RX 731'945 6'315'739 3'606'678
Zerocopy RX 764'041 6'442'761 3'947'451
local pktgen, 4/6 CPUs, 1200 bytes, randomized flows, UDPCSUM:
Hits Missed Lost
Stock TX 2'071'030 17'929'192 16'807'785
Zerocopy TX 1'951'142 18'049'056 16'977'296
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Cc: Jesse Gross <redacted>
Cc: Eric Dumazet <redacted>
---
net/openvswitch/datapath.c | 47 ++++++++++++++++++++++++++++++++++++++++------
1 file changed, 41 insertions(+), 6 deletions(-)
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index f7e3a0d..c5927ad 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c@@ -383,10 +383,11 @@ 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 */
@@ -404,6 +405,7 @@ static int queue_userspace_packet(struct net *net, int dp_ifindex, struct sk_buff *nskb = NULL; struct sk_buff *user_skb; /* to be queued to userspace */ struct nlattr *nla; + unsigned int plen, hlen; int err; if (vlan_tx_tag_present(skb)) {
@@ -424,7 +426,12 @@ static int queue_userspace_packet(struct net *net, int dp_ifindex, goto out; } - user_skb = genlmsg_new(upcall_msg_size(skb, upcall_info->userdata), GFP_ATOMIC); + if (skb->ip_summed == CHECKSUM_PARTIAL && + (err = skb_checksum_help(skb))) + goto out; + + hlen = skb_zerocopy_headlen(skb); + user_skb = genlmsg_new(upcall_msg_size(skb, upcall_info->userdata, hlen), GFP_ATOMIC); if (!user_skb) { err = -ENOMEM; goto out;
@@ -443,11 +450,39 @@ 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); + 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); + + /* Align the end of the attribute to NLA_ALIGNTO */ + plen = NLA_ALIGN(user_skb->len) - user_skb->len; + if (plen > 0) { + int nr_frags = skb_shinfo(user_skb)->nr_frags; - skb_copy_and_csum_dev(skb, nla_data(nla)); + if (nr_frags) { + skb_frag_t *frag; + + /* Assumption is made that PAGE_SIZE is always alligned + * to at least NLA_ALIGNTO (4) which means that we it + * should be safe to add the padding bytes to the frag + */ + frag = &skb_shinfo(user_skb)->frags[nr_frags -1]; + skb_frag_size_add(frag, plen); + + user_skb->truesize += plen; + user_skb->len += plen; + user_skb->data_len += plen; + } else + memset(skb_put(user_skb, plen), 0, plen); + } + + /* Fix alignment of .nlmsg_len, OVS user space enforces a strict + * total message size alignment. + */ + ((struct nlmsghdr *) user_skb->data)->nlmsg_len = NLA_ALIGN(user_skb->len); - genlmsg_end(user_skb, upcall); err = genlmsg_unicast(net, user_skb, upcall_info->portid); out:
--
1.8.3.1