can: raw: use bitfields to store flags in struct raw_sock

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The bound, loopback, recv_own_msgs, fd_frames, xl_frames and
join_filters fields of struct raw_sock just need to store one bit of
information.

Declare all those members as a bitfields of type unsigned int and
width one bit.

Add a temporary variable to raw_setsockopt() and raw_getsockopt() to
make the conversion between the stored bits and the socket interface.

This reduces the size of struct raw_sock by sixteen bytes.

Statistics before:

  $ pahole --class_name=raw_sock net/can/raw.o
  struct raw_sock {
  	struct sock                sk __attribute__((__aligned__(8))); /*     0   776 */

  	/* XXX last struct has 1 bit hole */

  	/* --- cacheline 12 boundary (768 bytes) was 8 bytes ago --- */
  	int                        bound;                /*   776     4 */
  	int                        ifindex;              /*   780     4 */
  	struct net_device *        dev;                  /*   784     8 */
  	netdevice_tracker          dev_tracker;          /*   792     0 */
  	struct list_head           notifier;             /*   792    16 */
  	int                        loopback;             /*   808     4 */
  	int                        recv_own_msgs;        /*   812     4 */
  	int                        fd_frames;            /*   816     4 */
  	int                        xl_frames;            /*   820     4 */
  	struct can_raw_vcid_options raw_vcid_opts;       /*   824     4 */
  	canid_t                    tx_vcid_shifted;      /*   828     4 */
  	/* --- cacheline 13 boundary (832 bytes) --- */
  	canid_t                    rx_vcid_shifted;      /*   832     4 */
  	canid_t                    rx_vcid_mask_shifted; /*   836     4 */
  	int                        join_filters;         /*   840     4 */
  	int                        count;                /*   844     4 */
  	struct can_filter          dfilter;              /*   848     8 */
  	struct can_filter *        filter;               /*   856     8 */
  	can_err_mask_t             err_mask;             /*   864     4 */

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

  	struct uniqframe *         uniq;                 /*   872     8 */

  	/* size: 880, cachelines: 14, members: 20 */
  	/* sum members: 876, holes: 1, sum holes: 4 */
  	/* member types with bit holes: 1, total: 1 */
  	/* forced alignments: 1 */
  	/* last cacheline: 48 bytes */
  } __attribute__((__aligned__(8)));

...and after:

  $ pahole --class_name=raw_sock net/can/raw.o
  struct raw_sock {
  	struct sock                sk __attribute__((__aligned__(8))); /*     0   776 */

  	/* XXX last struct has 1 bit hole */

  	/* --- cacheline 12 boundary (768 bytes) was 8 bytes ago --- */
  	int                        ifindex;              /*   776     4 */

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

  	struct net_device *        dev;                  /*   784     8 */
  	netdevice_tracker          dev_tracker;          /*   792     0 */
  	struct list_head           notifier;             /*   792    16 */
  	unsigned int               bound:1;              /*   808: 0  4 */
  	unsigned int               loopback:1;           /*   808: 1  4 */
  	unsigned int               recv_own_msgs:1;      /*   808: 2  4 */
  	unsigned int               fd_frames:1;          /*   808: 3  4 */
  	unsigned int               xl_frames:1;          /*   808: 4  4 */
  	unsigned int               join_filters:1;       /*   808: 5  4 */

  	/* XXX 2 bits hole, try to pack */
  	/* Bitfield combined with next fields */

  	struct can_raw_vcid_options raw_vcid_opts;       /*   809     4 */

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

  	canid_t                    tx_vcid_shifted;      /*   816     4 */
  	canid_t                    rx_vcid_shifted;      /*   820     4 */
  	canid_t                    rx_vcid_mask_shifted; /*   824     4 */
  	int                        count;                /*   828     4 */
  	/* --- cacheline 13 boundary (832 bytes) --- */
  	struct can_filter          dfilter;              /*   832     8 */
  	struct can_filter *        filter;               /*   840     8 */
  	can_err_mask_t             err_mask;             /*   848     4 */

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

  	struct uniqframe *         uniq;                 /*   856     8 */

  	/* size: 864, cachelines: 14, members: 20 */
  	/* sum members: 852, holes: 3, sum holes: 11 */
  	/* sum bitfield members: 6 bits, bit holes: 1, sum bit holes: 2 bits */
  	/* member types with bit holes: 1, total: 1 */
  	/* forced alignments: 1 */
  	/* last cacheline: 32 bytes */
  } __attribute__((__aligned__(8)));

Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Link: https://patch.msgid.link/20250917-can-raw-repack-v2-2-395e8b3a4437@kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

...

This commit is contained in:

Vincent Mailhol 2025-09-17 13:48:25 +09:00 • committed by Marc Kleine-Budde

parent fc8418eca4

commit 890e5198a6

1 changed files with 35 additions and 24 deletions

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net/can/raw.c

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