net: dsa: merge all bools of struct dsa_switch into a single u32

net: dsa: merge all bools of struct dsa_switch into a single u32

struct dsa_switch has 9 boolean properties, many of which are in fact
set by drivers for custom behavior (vlan_filtering_is_global,
needs_standalone_vlan_filtering, etc etc). The binary layout of the
structure could be improved. For example, the "bool setup" at the
beginning introduces a gratuitous 7 byte hole in the first cache line.

The change merges all boolean properties into bitfields of an u32, and
places that u32 in the first cache line of the structure, since many
bools are accessed from the data path (untag_bridge_pvid, vlan_filtering,
vlan_filtering_is_global).

We place this u32 after the existing ds->index, which is also 4 bytes in
size. As a positive side effect, ds->tagger_data now fits into the first
cache line too, because 4 bytes are saved.

Before:

pahole -C dsa_switch net/dsa/slave.o
struct dsa_switch {
        bool                       setup;                /*     0     1 */

        /* XXX 7 bytes hole, try to pack */

        struct device *            dev;                  /*     8     8 */
        struct dsa_switch_tree *   dst;                  /*    16     8 */
        unsigned int               index;                /*    24     4 */

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

        struct notifier_block      nb;                   /*    32    24 */

        /* XXX last struct has 4 bytes of padding */

        void *                     priv;                 /*    56     8 */
        /* --- cacheline 1 boundary (64 bytes) --- */
        void *                     tagger_data;          /*    64     8 */
        struct dsa_chip_data *     cd;                   /*    72     8 */
        const struct dsa_switch_ops  * ops;              /*    80     8 */
        u32                        phys_mii_mask;        /*    88     4 */

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

        struct mii_bus *           slave_mii_bus;        /*    96     8 */
        unsigned int               ageing_time_min;      /*   104     4 */
        unsigned int               ageing_time_max;      /*   108     4 */
        struct dsa_8021q_context * tag_8021q_ctx;        /*   112     8 */
        struct devlink *           devlink;              /*   120     8 */
        /* --- cacheline 2 boundary (128 bytes) --- */
        unsigned int               num_tx_queues;        /*   128     4 */
        bool                       vlan_filtering_is_global; /*   132     1 */
        bool                       needs_standalone_vlan_filtering; /*   133     1 */
        bool                       configure_vlan_while_not_filtering; /*   134     1 */
        bool                       untag_bridge_pvid;    /*   135     1 */
        bool                       assisted_learning_on_cpu_port; /*   136     1 */
        bool                       vlan_filtering;       /*   137     1 */
        bool                       pcs_poll;             /*   138     1 */
        bool                       mtu_enforcement_ingress; /*   139     1 */
        unsigned int               num_lag_ids;          /*   140     4 */
        unsigned int               max_num_bridges;      /*   144     4 */

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

        size_t                     num_ports;            /*   152     8 */

        /* size: 160, cachelines: 3, members: 27 */
        /* sum members: 141, holes: 4, sum holes: 19 */
        /* paddings: 1, sum paddings: 4 */
        /* last cacheline: 32 bytes */
};

After:

pahole -C dsa_switch net/dsa/slave.o
struct dsa_switch {
        struct device *            dev;                  /*     0     8 */
        struct dsa_switch_tree *   dst;                  /*     8     8 */
        unsigned int               index;                /*    16     4 */
        u32                        setup:1;              /*    20: 0  4 */
        u32                        vlan_filtering_is_global:1; /*    20: 1  4 */
        u32                        needs_standalone_vlan_filtering:1; /*    20: 2  4 */
        u32                        configure_vlan_while_not_filtering:1; /*    20: 3  4 */
        u32                        untag_bridge_pvid:1;  /*    20: 4  4 */
        u32                        assisted_learning_on_cpu_port:1; /*    20: 5  4 */
        u32                        vlan_filtering:1;     /*    20: 6  4 */
        u32                        pcs_poll:1;           /*    20: 7  4 */
        u32                        mtu_enforcement_ingress:1; /*    20: 8  4 */

        /* XXX 23 bits hole, try to pack */

        struct notifier_block      nb;                   /*    24    24 */

        /* XXX last struct has 4 bytes of padding */

        void *                     priv;                 /*    48     8 */
        void *                     tagger_data;          /*    56     8 */
        /* --- cacheline 1 boundary (64 bytes) --- */
        struct dsa_chip_data *     cd;                   /*    64     8 */
        const struct dsa_switch_ops  * ops;              /*    72     8 */
        u32                        phys_mii_mask;        /*    80     4 */

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

        struct mii_bus *           slave_mii_bus;        /*    88     8 */
        unsigned int               ageing_time_min;      /*    96     4 */
        unsigned int               ageing_time_max;      /*   100     4 */
        struct dsa_8021q_context * tag_8021q_ctx;        /*   104     8 */
        struct devlink *           devlink;              /*   112     8 */
        unsigned int               num_tx_queues;        /*   120     4 */
        unsigned int               num_lag_ids;          /*   124     4 */
        /* --- cacheline 2 boundary (128 bytes) --- */
        unsigned int               max_num_bridges;      /*   128     4 */

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

        size_t                     num_ports;            /*   136     8 */

        /* size: 144, cachelines: 3, members: 27 */
        /* sum members: 132, holes: 2, sum holes: 8 */
        /* sum bitfield members: 9 bits, bit holes: 1, sum bit holes: 23 bits */
        /* paddings: 1, sum paddings: 4 */
        /* last cacheline: 16 bytes */
};

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>