[PATCH v2 0/3] can: raw: optimize the sizes of struct uniqframe and struct raw_sock

[PATCH v2 0/3] can: raw: optimize the sizes of struct uniqframe and struct raw_sock

[Vincent Mailhol]

A few bytes can be shaved out of can raw's struct uniqframe and struct
raw_sock.

Patch #1 reorders struct uniqframe fields to save 8 bytes.

Patch #2 and #3 modify struct raw_sock to use bitfields and to reorder
its fields to save 24 bytes in total.

Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
---
Changes in v2:

  - in patch #2 also add raw_sock->bound and raw_sock->join_filters to
    the bitfield.

  - add Oliver's Ack tags.

Link to v1: https://lore.kernel.org/r/20250915-can-raw-repack-v1-0-5ea293bc6d33@kernel.org

---
Vincent Mailhol (3):
      can: raw: reorder struct uniqframe's members to optimise packing
      can: raw: use bitfields to store flags in struct raw_sock
      can: raw: reorder struct raw_sock's members to optimise packing

 net/can/raw.c | 65 ++++++++++++++++++++++++++++++++++-------------------------
 1 file changed, 38 insertions(+), 27 deletions(-)
---
base-commit: 5e87fdc37f8dc619549d49ba5c951b369ce7c136
change-id: 20250915-can-raw-repack-c21aab25cc11

Best regards,
-- 
Vincent Mailhol <mailhol@kernel.org>

[PATCH v2 1/3] can: raw: reorder struct uniqframe's members to optimise packing

[Vincent Mailhol]

struct uniqframe has one hole. Reorder the fields to save 8 bytes.

Statistics before:

  $ pahole --class_name=uniqframe net/can/raw.o
  struct uniqframe {
  	int                        skbcnt;               /*     0     4 */

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

  	const struct sk_buff  *    skb;                  /*     8     8 */
  	unsigned int               join_rx_count;        /*    16     4 */

  	/* size: 24, cachelines: 1, members: 3 */
  	/* sum members: 16, holes: 1, sum holes: 4 */
  	/* padding: 4 */
  	/* last cacheline: 24 bytes */
  };

...and after:

  $ pahole --class_name=uniqframe net/can/raw.o
  struct uniqframe {
  	const struct sk_buff  *    skb;                  /*     0     8 */
  	int                        skbcnt;               /*     8     4 */
  	unsigned int               join_rx_count;        /*    12     4 */

  	/* size: 16, cachelines: 1, members: 3 */
  	/* last cacheline: 16 bytes */
  };

Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
---
 net/can/raw.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/can/raw.c b/net/can/raw.c
index 76b867d21def209f5c6d236604c0e434a1c55a4d..db21d8a8c54d1b6a25a72c7a9d11d5c94f3187b5 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -75,8 +75,8 @@ MODULE_ALIAS("can-proto-1");
  */
 
 struct uniqframe {
-	int skbcnt;
 	const struct sk_buff *skb;
+	int skbcnt;
 	unsigned int join_rx_count;
 };
 

-- 
2.49.1

[PATCH v2 2/3] can: raw: use bitfields to store flags in struct raw_sock

[Vincent Mailhol]

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>
---
Changelog:

v1 -> v2:

  - also add raw_sock->bound and raw_sock->join_filters to the
    bitfield
---
 net/can/raw.c | 59 +++++++++++++++++++++++++++++++++++------------------------
 1 file changed, 35 insertions(+), 24 deletions(-)

diff --git a/net/can/raw.c b/net/can/raw.c
index db21d8a8c54d1b6a25a72c7a9d11d5c94f3187b5..5a5ded519cd1768456c234c42dc4e865f7350dab 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -82,20 +82,20 @@ struct uniqframe {
 
 struct raw_sock {
 	struct sock sk;
-	int bound;
 	int ifindex;
 	struct net_device *dev;
 	netdevice_tracker dev_tracker;
 	struct list_head notifier;
-	int loopback;
-	int recv_own_msgs;
-	int fd_frames;
-	int xl_frames;
+	unsigned int bound:1;
+	unsigned int loopback:1;
+	unsigned int recv_own_msgs:1;
+	unsigned int fd_frames:1;
+	unsigned int xl_frames:1;
+	unsigned int join_filters:1;
 	struct can_raw_vcid_options raw_vcid_opts;
 	canid_t tx_vcid_shifted;
 	canid_t rx_vcid_shifted;
 	canid_t rx_vcid_mask_shifted;
-	int join_filters;
 	int count;                 /* number of active filters */
 	struct can_filter dfilter; /* default/single filter */
 	struct can_filter *filter; /* pointer to filter(s) */
@@ -560,8 +560,8 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
 	struct can_filter sfilter;         /* single filter */
 	struct net_device *dev = NULL;
 	can_err_mask_t err_mask = 0;
-	int fd_frames;
 	int count = 0;
+	int flag;
 	int err = 0;
 
 	if (level != SOL_CAN_RAW)
@@ -682,44 +682,48 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
 		break;
 
 	case CAN_RAW_LOOPBACK:
-		if (optlen != sizeof(ro->loopback))
+		if (optlen != sizeof(flag))
 			return -EINVAL;
 
-		if (copy_from_sockptr(&ro->loopback, optval, optlen))
+		if (copy_from_sockptr(&flag, optval, optlen))
 			return -EFAULT;
 
+		ro->loopback = !!flag;
 		break;
 
 	case CAN_RAW_RECV_OWN_MSGS:
-		if (optlen != sizeof(ro->recv_own_msgs))
+		if (optlen != sizeof(flag))
 			return -EINVAL;
 
-		if (copy_from_sockptr(&ro->recv_own_msgs, optval, optlen))
+		if (copy_from_sockptr(&flag, optval, optlen))
 			return -EFAULT;
 
+		ro->recv_own_msgs = !!flag;
 		break;
 
 	case CAN_RAW_FD_FRAMES:
-		if (optlen != sizeof(fd_frames))
+		if (optlen != sizeof(flag))
 			return -EINVAL;
 
-		if (copy_from_sockptr(&fd_frames, optval, optlen))
+		if (copy_from_sockptr(&flag, optval, optlen))
 			return -EFAULT;
 
 		/* Enabling CAN XL includes CAN FD */
-		if (ro->xl_frames && !fd_frames)
+		if (ro->xl_frames && !flag)
 			return -EINVAL;
 
-		ro->fd_frames = fd_frames;
+		ro->fd_frames = !!flag;
 		break;
 
 	case CAN_RAW_XL_FRAMES:
-		if (optlen != sizeof(ro->xl_frames))
+		if (optlen != sizeof(flag))
 			return -EINVAL;
 
-		if (copy_from_sockptr(&ro->xl_frames, optval, optlen))
+		if (copy_from_sockptr(&flag, optval, optlen))
 			return -EFAULT;
 
+		ro->xl_frames = !!flag;
+
 		/* Enabling CAN XL includes CAN FD */
 		if (ro->xl_frames)
 			ro->fd_frames = ro->xl_frames;
@@ -739,12 +743,13 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
 		break;
 
 	case CAN_RAW_JOIN_FILTERS:
-		if (optlen != sizeof(ro->join_filters))
+		if (optlen != sizeof(flag))
 			return -EINVAL;
 
-		if (copy_from_sockptr(&ro->join_filters, optval, optlen))
+		if (copy_from_sockptr(&flag, optval, optlen))
 			return -EFAULT;
 
+		ro->join_filters = !!flag;
 		break;
 
 	default:
@@ -758,6 +763,7 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
 {
 	struct sock *sk = sock->sk;
 	struct raw_sock *ro = raw_sk(sk);
+	int flag;
 	int len;
 	void *val;
 
@@ -806,25 +812,29 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
 	case CAN_RAW_LOOPBACK:
 		if (len > sizeof(int))
 			len = sizeof(int);
-		val = &ro->loopback;
+		flag = ro->loopback;
+		val = &flag;
 		break;
 
 	case CAN_RAW_RECV_OWN_MSGS:
 		if (len > sizeof(int))
 			len = sizeof(int);
-		val = &ro->recv_own_msgs;
+		flag = ro->recv_own_msgs;
+		val = &flag;
 		break;
 
 	case CAN_RAW_FD_FRAMES:
 		if (len > sizeof(int))
 			len = sizeof(int);
-		val = &ro->fd_frames;
+		flag = ro->fd_frames;
+		val = &flag;
 		break;
 
 	case CAN_RAW_XL_FRAMES:
 		if (len > sizeof(int))
 			len = sizeof(int);
-		val = &ro->xl_frames;
+		flag = ro->xl_frames;
+		val = &flag;
 		break;
 
 	case CAN_RAW_XL_VCID_OPTS: {
@@ -849,7 +859,8 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
 	case CAN_RAW_JOIN_FILTERS:
 		if (len > sizeof(int))
 			len = sizeof(int);
-		val = &ro->join_filters;
+		flag = ro->join_filters;
+		val = &flag;
 		break;
 
 	default:

-- 
2.49.1

[PATCH v2 3/3] can: raw: reorder struct raw_sock's members to optimise packing

[Vincent Mailhol]

struct raw_sock has several holes. Reorder the fields to save 8 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                        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)));

...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 --- */
  	struct net_device *        dev;                  /*   776     8 */
  	netdevice_tracker          dev_tracker;          /*   784     0 */
  	struct list_head           notifier;             /*   784    16 */
  	int                        ifindex;              /*   800     4 */
  	unsigned int               bound:1;              /*   804: 0  4 */
  	unsigned int               loopback:1;           /*   804: 1  4 */
  	unsigned int               recv_own_msgs:1;      /*   804: 2  4 */
  	unsigned int               fd_frames:1;          /*   804: 3  4 */
  	unsigned int               xl_frames:1;          /*   804: 4  4 */
  	unsigned int               join_filters:1;       /*   804: 5  4 */

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

  	struct can_raw_vcid_options raw_vcid_opts;       /*   805     4 */

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

  	canid_t                    tx_vcid_shifted;      /*   812     4 */
  	canid_t                    rx_vcid_shifted;      /*   816     4 */
  	canid_t                    rx_vcid_mask_shifted; /*   820     4 */
  	can_err_mask_t             err_mask;             /*   824     4 */
  	int                        count;                /*   828     4 */
  	/* --- cacheline 13 boundary (832 bytes) --- */
  	struct can_filter          dfilter;              /*   832     8 */
  	struct can_filter *        filter;               /*   840     8 */
  	struct uniqframe *         uniq;                 /*   848     8 */

  	/* size: 856, cachelines: 14, members: 20 */
  	/* sum members: 852, holes: 1, sum holes: 3 */
  	/* 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: 24 bytes */
  } __attribute__((__aligned__(8)));

Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
---
 net/can/raw.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/can/raw.c b/net/can/raw.c
index 5a5ded519cd1768456c234c42dc4e865f7350dab..bf65d67b5df0135bf02d90c5e1070898a4f5592e 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -82,10 +82,10 @@ struct uniqframe {
 
 struct raw_sock {
 	struct sock sk;
-	int ifindex;
 	struct net_device *dev;
 	netdevice_tracker dev_tracker;
 	struct list_head notifier;
+	int ifindex;
 	unsigned int bound:1;
 	unsigned int loopback:1;
 	unsigned int recv_own_msgs:1;
@@ -96,10 +96,10 @@ struct raw_sock {
 	canid_t tx_vcid_shifted;
 	canid_t rx_vcid_shifted;
 	canid_t rx_vcid_mask_shifted;
+	can_err_mask_t err_mask;
 	int count;                 /* number of active filters */
 	struct can_filter dfilter; /* default/single filter */
 	struct can_filter *filter; /* pointer to filter(s) */
-	can_err_mask_t err_mask;
 	struct uniqframe __percpu *uniq;
 };
 

-- 
2.49.1

Re: [PATCH v2 0/3] can: raw: optimize the sizes of struct uniqframe and struct raw_sock

[Marc Kleine-Budde]

[-- Attachment #1: Type: text/plain, Size: 694 bytes --]

On 17.09.2025 13:48:23, Vincent Mailhol wrote:
> A few bytes can be shaved out of can raw's struct uniqframe and struct
> raw_sock.
> 
> Patch #1 reorders struct uniqframe fields to save 8 bytes.
> 
> Patch #2 and #3 modify struct raw_sock to use bitfields and to reorder
> its fields to save 24 bytes in total.
> 
> Signed-off-by: Vincent Mailhol <mailhol@kernel.org>

Applied to linux-can-next.

Thanks,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

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