net: optimize INET input path further

Followup of commit b178bb3dfc30 (net: reorder struct sock fields)

Optimize INET input path a bit further, by :

1) moving sk_refcnt close to sk_lock.

This reduces number of dirtied cache lines by one on 64bit arches (and
64 bytes cache line size).

2) moving inet_daddr & inet_rcv_saddr at the beginning of sk

(same cache line than hash / family / bound_dev_if / nulls_node)

This reduces number of accessed cache lines in lookups by one, and dont
increase size of inet and timewait socks.
inet and tw sockets now share same place-holder for these fields.

Before patch :

offsetof(struct sock, sk_refcnt) = 0x10
offsetof(struct sock, sk_lock) = 0x40
offsetof(struct sock, sk_receive_queue) = 0x60
offsetof(struct inet_sock, inet_daddr) = 0x270
offsetof(struct inet_sock, inet_rcv_saddr) = 0x274

After patch :

offsetof(struct sock, sk_refcnt) = 0x44
offsetof(struct sock, sk_lock) = 0x48
offsetof(struct sock, sk_receive_queue) = 0x68
offsetof(struct inet_sock, inet_daddr) = 0x0
offsetof(struct inet_sock, inet_rcv_saddr) = 0x4

compute_score() (udp or tcp) now use a single cache line per ignored
item, instead of two.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 24 insertions, 13 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 3482004e5c29..82e86034702f 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -105,10 +105,8 @@ struct net;
 
 /**
  *      struct sock_common - minimal network layer representation of sockets
- *      @skc_node: main hash linkage for various protocol lookup tables
- *      @skc_nulls_node: main hash linkage for TCP/UDP/UDP-Lite protocol
- *      @skc_refcnt: reference count
- *      @skc_tx_queue_mapping: tx queue number for this connection
+ *      @skc_daddr: Foreign IPv4 addr
+ *      @skc_rcv_saddr: Bound local IPv4 addr
  *      @skc_hash: hash value used with various protocol lookup tables
  *      @skc_u16hashes: two u16 hash values used by UDP lookup tables
  *      @skc_family: network address family
@@ -119,20 +117,20 @@ struct net;
  *      @skc_portaddr_node: second hash linkage for UDP/UDP-Lite protocol
  *      @skc_prot: protocol handlers inside a network family
  *      @skc_net: reference to the network namespace of this socket
+ *      @skc_node: main hash linkage for various protocol lookup tables
+ *      @skc_nulls_node: main hash linkage for TCP/UDP/UDP-Lite protocol
+ *      @skc_tx_queue_mapping: tx queue number for this connection
+ *      @skc_refcnt: reference count
  *
  *      This is the minimal network layer representation of sockets, the header
  *      for struct sock and struct inet_timewait_sock.
  */
 struct sock_common {
-        /*
-         * first fields are not copied in sock_copy()
+        /* skc_daddr and skc_rcv_saddr must be grouped :
+         * cf INET_MATCH() and INET_TW_MATCH()
          */
-        union {
-                struct hlist_node       skc_node;
-                struct hlist_nulls_node skc_nulls_node;
-        };
-        atomic_t                skc_refcnt;
-        int                     skc_tx_queue_mapping;
+        __be32                  skc_daddr;
+        __be32                  skc_rcv_saddr;
 
         union  {
                 unsigned int    skc_hash;
@@ -150,6 +148,18 @@ struct sock_common {
 #ifdef CONFIG_NET_NS
         struct net              *skc_net;
 #endif
+        /*
+         * fields between dontcopy_begin/dontcopy_end
+         * are not copied in sock_copy()
+         */
+        int                     skc_dontcopy_begin[0];
+        union {
+                struct hlist_node       skc_node;
+                struct hlist_nulls_node skc_nulls_node;
+        };
+        int                     skc_tx_queue_mapping;
+        atomic_t                skc_refcnt;
+        int                     skc_dontcopy_end[0];
 };
 
 /**
@@ -232,7 +242,8 @@ struct sock {
 #define sk_refcnt               __sk_common.skc_refcnt
 #define sk_tx_queue_mapping     __sk_common.skc_tx_queue_mapping
 
-#define sk_copy_start           __sk_common.skc_hash
+#define sk_dontcopy_begin       __sk_common.skc_dontcopy_begin
+#define sk_dontcopy_end         __sk_common.skc_dontcopy_end
 #define sk_hash                 __sk_common.skc_hash
 #define sk_family               __sk_common.skc_family
 #define sk_state                __sk_common.skc_state