On Sun, Jun 18, 2023 at 6:16 AM Christophe JAILLET
<christophe.jaillet@xxxxxxxxxx> wrote:
>
> Group some variables based on their sizes to reduce hole and avoid padding.
> On x86_64, this shrinks the size of 'struct netlbl_domaddr6_map'
> from 72 to 64 bytes.
>
> It saves a few bytes of memory and is more cache-line friendly.
>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> ---
> Using pahole
>
> Before:
> ======
> struct netlbl_dom_map {
> char * domain; /* 0 8 */
> u16 family; /* 8 2 */
>
> /* XXX 6 bytes hole, try to pack */
>
> struct netlbl_dommap_def def; /* 16 16 */
> u32 valid; /* 32 4 */
>
> /* XXX 4 bytes hole, try to pack */
>
> struct list_head list; /* 40 16 */
> struct callback_head rcu __attribute__((__aligned__(8))); /* 56 16 */
>
> /* size: 72, cachelines: 2, members: 6 */
> /* sum members: 62, holes: 2, sum holes: 10 */
> /* forced alignments: 1 */
> /* last cacheline: 8 bytes */
> } __attribute__((__aligned__(8)));
>
>
> After:
> =====
> struct netlbl_dom_map {
> char * domain; /* 0 8 */
> struct netlbl_dommap_def def; /* 8 16 */
> u16 family; /* 24 2 */
>
> /* XXX 2 bytes hole, try to pack */
>
> u32 valid; /* 28 4 */
> struct list_head list; /* 32 16 */
> struct callback_head rcu __attribute__((__aligned__(8))); /* 48 16 */
>
> /* size: 64, cachelines: 1, members: 6 */
> /* sum members: 62, holes: 1, sum holes: 2 */
> /* forced alignments: 1 */
> } __attribute__((__aligned__(8)));
> ---
> net/netlabel/netlabel_domainhash.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx>
--
paul-moore.com
