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Date: Thu, 25 Jul 2013 14:43:45 +0200
From: Thomas Graf <tgraf@...g.ch>
To: davem@...emloft.net, jesse@...ira.com
Cc: netdev@...r.kernel.org, dev@...nvswitch.org,
eric.dumazet@...il.com, Thomas Graf <tgraf@...ap.localdomain>
Subject: [PATCH net-next 2/2] openvswitch: Use skb_zerocopy() to prepare skb for upcall
From: Thomas Graf <tgraf@...ap.localdomain>
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@...g.ch>
Cc: Jesse Gross <jesse@...ira.com>
Cc: Eric Dumazet <eric.dumazet@...il.com>
---
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
--
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