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 ddcebc53224f..a292bf8ad75c 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. */