net 01/05: fib_rules: rearrange struct fib_rule
Patrick McHardy [Thu, 3 Dec 2009 01:25:53 +0000 (01:25 +0000)]
commit b8952893d5d86f69c4e499d191b98c6658f64b0f
Author: Patrick McHardy <kaber@trash.net>
Date:   Thu Dec 3 12:05:22 2009 +0100

    net: fib_rules: rearrange struct fib_rule

    The ifname member is only used to resolve interface names and is not needed
    during rule lookups. The target and ctarget members however are used during
    rule lookups and are currently located in a second cacheline.

    Move ifname further to the end to make sure both target and ctarget are
    located in the same cacheline as other members used during rule lookups.

    The layout on 64 bit changes from:

    struct fib_rule {
     ...
            u32                        table;                /*    56     4 */
            u8                         action;               /*    60     1 */

            /* XXX 3 bytes hole, try to pack */

            /* --- cacheline 1 boundary (64 bytes) --- */
            u32                        target;               /*    64     4 */

            /* XXX 4 bytes hole, try to pack */

            struct fib_rule *          ctarget;              /*    72     8 */
            struct rcu_head            rcu;                  /*    80    16 */
            struct net *               fr_net;               /*    96     8 */
    };

    to:

    struct fib_rule {
     ...
            u32                        table;                /*    40     4 */
            u8                         action;               /*    44     1 */

            /* XXX 3 bytes hole, try to pack */

            u32                        target;               /*    48     4 */

            /* XXX 4 bytes hole, try to pack */

            struct fib_rule *          ctarget;              /*    56     8 */
            /* --- cacheline 1 boundary (64 bytes) --- */
            char                       ifname[16];           /*    64    16 */
            struct rcu_head            rcu;                  /*    80    16 */
            struct net *               fr_net;               /*    96     8 */

    };

Signed-off-by: Patrick McHardy <kaber@trash.net>

Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/fib_rules.h

index 2cd707b..22fb323 100644 (file)
@@ -11,7 +11,6 @@ struct fib_rule {
        struct list_head        list;
        atomic_t                refcnt;
        int                     ifindex;
-       char                    ifname[IFNAMSIZ];
        u32                     mark;
        u32                     mark_mask;
        u32                     pref;
@@ -20,6 +19,7 @@ struct fib_rule {
        u8                      action;
        u32                     target;
        struct fib_rule *       ctarget;
+       char                    ifname[IFNAMSIZ];
        struct rcu_head         rcu;
        struct net *            fr_net;
 };