4c9258dd26
Save eight bytes of holes on x86-64 architectures by reordering struct
can_priv members.
Before:
$ pahole -C can_priv drivers/net/can/dev/dev.o
struct can_priv {
struct net_device * dev; /* 0 8 */
struct can_device_stats can_stats; /* 8 24 */
struct can_bittiming bittiming; /* 32 32 */
/* --- cacheline 1 boundary (64 bytes) --- */
struct can_bittiming data_bittiming; /* 64 32 */
const struct can_bittiming_const * bittiming_const; /* 96 8 */
const struct can_bittiming_const * data_bittiming_const; /* 104 8 */
struct can_tdc tdc; /* 112 12 */
/* XXX 4 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
const struct can_tdc_const * tdc_const; /* 128 8 */
const u16 * termination_const; /* 136 8 */
unsigned int termination_const_cnt; /* 144 4 */
u16 termination; /* 148 2 */
/* XXX 2 bytes hole, try to pack */
const u32 * bitrate_const; /* 152 8 */
unsigned int bitrate_const_cnt; /* 160 4 */
/* XXX 4 bytes hole, try to pack */
const u32 * data_bitrate_const; /* 168 8 */
unsigned int data_bitrate_const_cnt; /* 176 4 */
u32 bitrate_max; /* 180 4 */
struct can_clock clock; /* 184 4 */
enum can_state state; /* 188 4 */
/* --- cacheline 3 boundary (192 bytes) --- */
u32 ctrlmode; /* 192 4 */
u32 ctrlmode_supported; /* 196 4 */
u32 ctrlmode_static; /* 200 4 */
int restart_ms; /* 204 4 */
struct delayed_work restart_work; /* 208 168 */
/* XXX last struct has 4 bytes of padding */
/* --- cacheline 5 boundary (320 bytes) was 56 bytes ago --- */
int (*do_set_bittiming)(struct net_device *); /* 376 8 */
/* --- cacheline 6 boundary (384 bytes) --- */
int (*do_set_data_bittiming)(struct net_device *); /* 384 8 */
int (*do_set_mode)(struct net_device *, enum can_mode); /* 392 8 */
int (*do_set_termination)(struct net_device *, u16); /* 400 8 */
int (*do_get_state)(const struct net_device *, enum can_state *); /* 408 8 */
int (*do_get_berr_counter)(const struct net_device *, struct can_berr_counter *); /* 416 8 */
unsigned int echo_skb_max; /* 424 4 */
/* XXX 4 bytes hole, try to pack */
struct sk_buff * * echo_skb; /* 432 8 */
/* size: 440, cachelines: 7, members: 31 */
/* sum members: 426, holes: 4, sum holes: 14 */
/* paddings: 1, sum paddings: 4 */
/* last cacheline: 56 bytes */
};
After:
$ pahole -C can_priv drivers/net/can/dev/dev.o
struct can_priv {
struct net_device * dev; /* 0 8 */
struct can_device_stats can_stats; /* 8 24 */
const struct can_bittiming_const * bittiming_const; /* 32 8 */
const struct can_bittiming_const * data_bittiming_const; /* 40 8 */
struct can_bittiming bittiming; /* 48 32 */
/* --- cacheline 1 boundary (64 bytes) was 16 bytes ago --- */
struct can_bittiming data_bittiming; /* 80 32 */
const struct can_tdc_const * tdc_const; /* 112 8 */
struct can_tdc tdc; /* 120 12 */
/* --- cacheline 2 boundary (128 bytes) was 4 bytes ago --- */
unsigned int bitrate_const_cnt; /* 132 4 */
const u32 * bitrate_const; /* 136 8 */
const u32 * data_bitrate_const; /* 144 8 */
unsigned int data_bitrate_const_cnt; /* 152 4 */
u32 bitrate_max; /* 156 4 */
struct can_clock clock; /* 160 4 */
unsigned int termination_const_cnt; /* 164 4 */
const u16 * termination_const; /* 168 8 */
u16 termination; /* 176 2 */
/* XXX 2 bytes hole, try to pack */
enum can_state state; /* 180 4 */
u32 ctrlmode; /* 184 4 */
u32 ctrlmode_supported; /* 188 4 */
/* --- cacheline 3 boundary (192 bytes) --- */
u32 ctrlmode_static; /* 192 4 */
int restart_ms; /* 196 4 */
struct delayed_work restart_work; /* 200 168 */
/* XXX last struct has 4 bytes of padding */
/* --- cacheline 5 boundary (320 bytes) was 48 bytes ago --- */
int (*do_set_bittiming)(struct net_device *); /* 368 8 */
int (*do_set_data_bittiming)(struct net_device *); /* 376 8 */
/* --- cacheline 6 boundary (384 bytes) --- */
int (*do_set_mode)(struct net_device *, enum can_mode); /* 384 8 */
int (*do_set_termination)(struct net_device *, u16); /* 392 8 */
int (*do_get_state)(const struct net_device *, enum can_state *); /* 400 8 */
int (*do_get_berr_counter)(const struct net_device *, struct can_berr_counter *); /* 408 8 */
unsigned int echo_skb_max; /* 416 4 */
/* XXX 4 bytes hole, try to pack */
struct sk_buff * * echo_skb; /* 424 8 */
/* size: 432, cachelines: 7, members: 31 */
/* sum members: 426, holes: 2, sum holes: 6 */
/* paddings: 1, sum paddings: 4 */
/* last cacheline: 48 bytes */
};
Link: https://lore.kernel.org/r/20210224002008.4158-3-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.