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Message-Id: <20250917-can-raw-repack-v2-3-395e8b3a4437@kernel.org>
Date: Wed, 17 Sep 2025 13:48:26 +0900
From: Vincent Mailhol <mailhol@...nel.org>
To: Oliver Hartkopp <socketcan@...tkopp.net>,
Marc Kleine-Budde <mkl@...gutronix.de>
Cc: linux-can@...r.kernel.org, linux-kernel@...r.kernel.org,
Christophe Jaillet <christophe.jaillet@...adoo.fr>,
Vincent Mailhol <mailhol@...nel.org>
Subject: [PATCH v2 3/3] can: raw: reorder struct raw_sock's members to
optimise packing
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@...tkopp.net>
Signed-off-by: Vincent Mailhol <mailhol@...nel.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
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