netdev - [PATCH v2 net-next 7/7] net: dsa: combine two holes in struct dsa_switch

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Date:   Wed,  5 Jan 2022 15:21:41 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: [PATCH v2 net-next 7/7] net: dsa: combine two holes in struct dsa_switch_tree

There is a 7 byte hole after dst->setup and a 4 byte hole after
dst->default_proto. Combining them, we have a single hole of just 3
bytes on 64 bit machines.

Before:

pahole -C dsa_switch_tree net/dsa/slave.o
struct dsa_switch_tree {
        struct list_head           list;                 /*     0    16 */
        struct list_head           ports;                /*    16    16 */
        struct raw_notifier_head   nh;                   /*    32     8 */
        unsigned int               index;                /*    40     4 */
        struct kref                refcount;             /*    44     4 */
        struct net_device * *      lags;                 /*    48     8 */
        bool                       setup;                /*    56     1 */

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

        /* --- cacheline 1 boundary (64 bytes) --- */
        const struct dsa_device_ops  * tag_ops;          /*    64     8 */
        enum dsa_tag_protocol      default_proto;        /*    72     4 */

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

        struct dsa_platform_data * pd;                   /*    80     8 */
        struct list_head           rtable;               /*    88    16 */
        unsigned int               lags_len;             /*   104     4 */
        unsigned int               last_switch;          /*   108     4 */

        /* size: 112, cachelines: 2, members: 13 */
        /* sum members: 101, holes: 2, sum holes: 11 */
        /* last cacheline: 48 bytes */
};

After:

pahole -C dsa_switch_tree net/dsa/slave.o
struct dsa_switch_tree {
        struct list_head           list;                 /*     0    16 */
        struct list_head           ports;                /*    16    16 */
        struct raw_notifier_head   nh;                   /*    32     8 */
        unsigned int               index;                /*    40     4 */
        struct kref                refcount;             /*    44     4 */
        struct net_device * *      lags;                 /*    48     8 */
        const struct dsa_device_ops  * tag_ops;          /*    56     8 */
        /* --- cacheline 1 boundary (64 bytes) --- */
        enum dsa_tag_protocol      default_proto;        /*    64     4 */
        bool                       setup;                /*    68     1 */

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

        struct dsa_platform_data * pd;                   /*    72     8 */
        struct list_head           rtable;               /*    80    16 */
        unsigned int               lags_len;             /*    96     4 */
        unsigned int               last_switch;          /*   100     4 */

        /* size: 104, cachelines: 2, members: 13 */
        /* sum members: 101, holes: 1, sum holes: 3 */
        /* last cacheline: 40 bytes */
};

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 include/net/dsa.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/net/dsa.h b/include/net/dsa.h
index cbbac75138d9..5d0fec6db3ae 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -136,9 +136,6 @@ struct dsa_switch_tree {
 	 */
 	struct net_device **lags;
 
-	/* Has this tree been applied to the hardware? */
-	bool setup;
-
 	/* Tagging protocol operations */
 	const struct dsa_device_ops *tag_ops;
 
@@ -147,6 +144,9 @@ struct dsa_switch_tree {
 	 */
 	enum dsa_tag_protocol default_proto;
 
+	/* Has this tree been applied to the hardware? */
+	bool setup;
+
 	/*
 	 * Configuration data for the platform device that owns
 	 * this dsa switch tree instance.
-- 
2.25.1