openvswitch: Compact sw_flow_key.

Minimize padding in sw_flow_key and move 'tp' top the main struct.
These changes simplify code when accessing the transport port numbers
and the tcp flags, and makes the sw_flow_key 8 bytes smaller on 64-bit
systems (128->120 bytes).  These changes also make the keys for IPv4
packets to fit in one cache line.

There is a valid concern for safety of packing the struct
ovs_key_ipv4_tunnel, as it would be possible to take the address of
the tun_id member as a __be64 * which could result in unaligned access
in some systems. However:

- sw_flow_key itself is 64-bit aligned, so the tun_id within is
  always
  64-bit aligned.
- We never make arrays of ovs_key_ipv4_tunnel (which would force
  every
  second tun_key to be misaligned).
- We never take the address of the tun_id in to a __be64 *.
- Whereever we use struct ovs_key_ipv4_tunnel outside the
  sw_flow_key,
  it is in stack (on tunnel input functions), where compiler has full
  control of the alignment.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>

1 files changed, 11 insertions, 18 deletions

diff --git a/net/openvswitch/flow.h b/net/openvswitch/flow.h
index ddcebc53224..a292bf8ad75 100644
--- a/net/openvswitch/flow.h
+++ b/net/openvswitch/flow.h
@@ -47,7 +47,7 @@ struct ovs_key_ipv4_tunnel {
 	__be16 tun_flags;
 	u8   ipv4_tos;
 	u8   ipv4_ttl;
-};
+} __packed __aligned(4); /* Minimize padding. */
 
 static inline void ovs_flow_tun_key_init(struct ovs_key_ipv4_tunnel *tun_key,
 					 const struct iphdr *iph, __be64 tun_id,
@@ -71,7 +71,7 @@ struct sw_flow_key {
 		u32	priority;	/* Packet QoS priority. */
 		u32	skb_mark;	/* SKB mark. */
 		u16	in_port;	/* Input switch port (or DP_MAX_PORTS). */
-	} phy;
+	} __packed phy; /* Safe when right after 'tun_key'. */
 	struct {
 		u8     src[ETH_ALEN];	/* Ethernet source address. */
 		u8     dst[ETH_ALEN];	/* Ethernet destination address. */
@@ -84,23 +84,21 @@ struct sw_flow_key {
 		u8     ttl;		/* IP TTL/hop limit. */
 		u8     frag;		/* One of OVS_FRAG_TYPE_*. */
 	} ip;
+	struct {
+		__be16 src;		/* TCP/UDP/SCTP source port. */
+		__be16 dst;		/* TCP/UDP/SCTP destination port. */
+		__be16 flags;		/* TCP flags. */
+	} tp;
 	union {
 		struct {
 			struct {
 				__be32 src;	/* IP source address. */
 				__be32 dst;	/* IP destination address. */
 			} addr;
-			union {
-				struct {
-					__be16 src;		/* TCP/UDP/SCTP source port. */
-					__be16 dst;		/* TCP/UDP/SCTP destination port. */
-					__be16 flags;		/* TCP flags. */
-				} tp;
-				struct {
-					u8 sha[ETH_ALEN];	/* ARP source hardware address. */
-					u8 tha[ETH_ALEN];	/* ARP target hardware address. */
-				} arp;
-			};
+			struct {
+				u8 sha[ETH_ALEN];	/* ARP source hardware address. */
+				u8 tha[ETH_ALEN];	/* ARP target hardware address. */
+			} arp;
 		} ipv4;
 		struct {
 			struct {
@@ -109,11 +107,6 @@ struct sw_flow_key {
 			} addr;
 			__be32 label;			/* IPv6 flow label. */
 			struct {
-				__be16 src;		/* TCP/UDP/SCTP source port. */
-				__be16 dst;		/* TCP/UDP/SCTP destination port. */
-				__be16 flags;		/* TCP flags. */
-			} tp;
-			struct {
 				struct in6_addr target;	/* ND target address. */
 				u8 sll[ETH_ALEN];	/* ND source link layer address. */
 				u8 tll[ETH_ALEN];	/* ND target link layer address. */