Group some variables based on their sizes to reduce hole and avoid padding.
On x86_64, this shrinks the size of 'struct mptcp_pm_add_entry'
from 136 to 128 bytes.
It saves a few bytes of memory and is more cache-line friendly.
Signed-off-by: Christophe JAILLET <[email protected]>
---
Using pahole
Before:
======
struct mptcp_pm_add_entry {
struct list_head list; /* 0 16 */
struct mptcp_addr_info addr; /* 16 12 */
/* XXX 4 bytes hole, try to pack */
struct timer_list add_timer; /* 32 88 */
/* --- cacheline 1 boundary (64 bytes) was 56 bytes ago --- */
struct mptcp_sock * sock; /* 120 8 */
/* --- cacheline 2 boundary (128 bytes) --- */
u8 retrans_times; /* 128 1 */
/* size: 136, cachelines: 3, members: 5 */
/* sum members: 125, holes: 1, sum holes: 4 */
/* padding: 7 */
/* last cacheline: 8 bytes */
};
After:
=====
struct mptcp_pm_add_entry {
struct list_head list; /* 0 16 */
struct mptcp_addr_info addr; /* 16 12 */
u8 retrans_times; /* 28 1 */
/* XXX 3 bytes hole, try to pack */
struct timer_list add_timer; /* 32 88 */
/* --- cacheline 1 boundary (64 bytes) was 56 bytes ago --- */
struct mptcp_sock * sock; /* 120 8 */
/* size: 128, cachelines: 2, members: 5 */
/* sum members: 125, holes: 1, sum holes: 3 */
};
---
net/mptcp/pm_netlink.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index a12a87b780f6..a56718ffdd02 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -25,9 +25,9 @@ static int pm_nl_pernet_id;
struct mptcp_pm_add_entry {
struct list_head list;
struct mptcp_addr_info addr;
+ u8 retrans_times;
struct timer_list add_timer;
struct mptcp_sock *sock;
- u8 retrans_times;
};
struct pm_nl_pernet {
--
2.34.1
Hi Christophe,
On 18/06/2023 11:46, Christophe JAILLET wrote:
> Group some variables based on their sizes to reduce hole and avoid padding.
> On x86_64, this shrinks the size of 'struct mptcp_pm_add_entry'
> from 136 to 128 bytes.
>
> It saves a few bytes of memory and is more cache-line friendly.
Good catch and thank you for having shared this patch, it looks good to me!
Reviewed-by: Matthieu Baerts <[email protected]>
Cheers,
Matt
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Sun, Jun 18, 2023 at 11:46:46AM CEST, [email protected] wrote:
>Group some variables based on their sizes to reduce hole and avoid padding.
>On x86_64, this shrinks the size of 'struct mptcp_pm_add_entry'
>from 136 to 128 bytes.
>
>It saves a few bytes of memory and is more cache-line friendly.
>
>Signed-off-by: Christophe JAILLET <[email protected]>
Reviewed-by: Jiri Pirko <[email protected]>
Hello:
This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <[email protected]>:
On Sun, 18 Jun 2023 11:46:46 +0200 you wrote:
> Group some variables based on their sizes to reduce hole and avoid padding.
> On x86_64, this shrinks the size of 'struct mptcp_pm_add_entry'
> from 136 to 128 bytes.
>
> It saves a few bytes of memory and is more cache-line friendly.
>
> Signed-off-by: Christophe JAILLET <[email protected]>
>
> [...]
Here is the summary with links:
- [net-next] mptcp: Reorder fields in 'struct mptcp_pm_add_entry'
https://git.kernel.org/netdev/net-next/c/92b08290859b
You are awesome, thank you!
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